BW66 can't be figured out

XJ
1

Hi and thank you for reading, in advance.

Before you ask, I went through the workshop manual, the haynes copy and most of the internet.
My gearbox was among the few parts of my XJ6 that worked flawlessly when I bought it. A few weeks ago, however, it emitted a creaking noise on acceleration which I first thought to be wheel spin related, but obviously it wasn’t. There is no flare, shift quality is okay.

I then topped of the fluid which was red but slightly low (hot side, went through all gears, oil hot, idling in P).
Stall test in first reproduced the creak (not the brakes).
What happened next was that the box decided to ignore my throttle commands, as in upshifts as soon as possible, no load relation. My guess then was, and still is that it had something to do with the TV, or kickdown cable: The line pressure too low / the cable disconnected should reproduce the mentioned issues, right?
So an hour ago I went out to make careful adjustments.

The cable pulls out with minimal resistance, albeit frayed (Which I knew of, so I threw a spare in the trunk just before things went downhill), I can feel slack, then resistance and then even more resistance which should be the kickdown - a ‘click’, then stop- and all that engages within normal pedal travel so it should be good, not stretched!
Didn’t mind the bands as it was a rather sudden change, gradually worsening afterwards and it changes gears via the lever albeit just as bad.
I went through the full cable adjustment range anyway, without any change in shift characteristics.

Stall test is creaking in drive, not so in reverse where it stalled around 2300 for a second and then went on to produce a wee bit of smoke and more rpms and as reverse uses only the rear band & clutch, I ruled out band adjustment as major issue… Also it whines in first which it always did, and seemingly this is normal.

So I guess I will need to adjust bands if there’s any lining left, also do the oil and filter and also adjust the tv cable cam. I do have a spare BW65, condition unknown, but don’t want to swap them. Wish it was a four speed overdrive. Also, I don’t really want to drive anywhere to swap.

Do you have any ideas, suggestions, help? Could something be blocked, clogged, jammed, broken?

(Truly!) yours, David

2

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Firstly, the stall test in ‘D’ should produce some 1950 - 2000 rpms, David - what did you get…?

Stall rpms is a measure of the slip between the impeller and the stator - basically verifying engine condition, and there is no slip in the box. Stall rpms in revers or any other gear is not spec’ed - and your reverse reading is inconclusive…?

Apart from the creaking; you do not mention the shift points in general. Certainly, the box should upshift very quickly under light pedal input/load; 1/2 at 8 - 12 mph and 2/3 at 13 - 19 mph. And also, at such speeds, should downshift if the pedal is pushed enough. The shiftpoints/pedal relations pertains to drivers wishes; light pedal a whish for economy, heavy pedal a whish for power - requiring rpm increase…

The downshift cable mechanically connects the gas pedal to a cam which in turn influences pressures and pressure distribution in the valve body - there should be no slack in the cable with the pedal released. if the cable stretches over time it can be readjusted at the throttle pedestal - as you tried…

The proper adjustment procedure involves a pressure gauge connected to the pressure take-off point - the main function of the adjustment is to ‘tune’ the gearbox to the engine. The box works on hydraulic pressures, but the box must ‘learn’ the pressures delivered from the engine driven pump - and how it varies with engine rpms.

So idling in ‘D’; the pressure is measured, and must be within spec limits. Rpms is then increased by 500 and again observed within specs - and the difference noted. This must also be within specs, but if not; the cable is adjusted (with engine stopped and the shift lever in ‘N’) - and the test is repeated until specs are reached. All set; a small ferrule is then crimped to the cable - 0.010" fro the adjuster…

With shift anomalies. the first step is to verify that the ferrule is present (and firmly attached to the cable) - then adjust cable to the spec distance. If ‘freehand’ adjustment is done (for minor shift anomalies) incremental adjustments must be used - the adjustment is very sensitive…

If, however, large adjustments are carried out with little effect; something is wrong - and the proper procedure should be used. As it should if the cable is replaced…

In your case; carefully check the cable’s attachment to box. The plastic ferrule at the box might be faulty and/or adrift, or the cable damaged - if so; adjustment at the pedal end is pointless…

Frank
xj6 85 Sov Europe (UK/NZ)
**

3

Thank you, Frank!

The stall speed in D is indeed too high and creaks so I didn’t investigate further.
As stall speed checks mainly the TC, but also the bands&clutches that hold the gear the test would give some information as to fault finding. Strange that both bands would slip at the same time, so I got hung up with pressure.
Upshifts are the same as if you were rolling downhill gaining speed, no downshift per pedal.

I will look for proper cable connection at the transmission end - good catch! There’s no ferrule at both cables I recall however when all is opened we could come close to the correct length, rest with gauge.
The fault key lists cleaning and dismantling valve bodies and to check the route to the pump; so that’s whats next. Also gives me hope, I fear I have missed that particular fault key.

I will report back when I performed the operation, of course with pressure gauge. I just wanted to get any kind of response with the adjustment and got desperate, read frustrated, to no avail!

Best regards, David

4

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The pressure test may indicate whether there is something deeper than a cable adjustment involved, David…

What was the actual stall speed? There is a difference between ‘normal’ 2100 rpms and ‘excessive/faulty’ past 2500 rpms which signifies clutch slipping. With no downshift from 20 mph in high gear with pedal action - did the car just accelerate in high with no slipping/engine flaring?

The gearbox has three pressure regulating inputs; the engine rpms, the governor (roadspeed) and pedal input - the box then decides what to do. The valve body uses the pressures to move spring loaded spool valves to open and close passages to the respective clutches and bands.

Lack of pedal inputs, faulty downshift cable, the box will basically upshift and downshift based on engine rpms and roadspeed, with no mechanical noises expected. Manual downshift (D2 and D1) will be normal, but 1/2 upshifts will behave as upshifts in ‘D’.

Faults in the valve body may give various symptoms, depending on the cause. Cleaning the valve body is complicated, and it is advisable to use a workshop manual to get all the bits back in their rightful places. Access to valve body. fluid and filter change requires removal of the pan as will changing the downshift cable - so a more careful inspection of the cable attachment should be done at the same time. Drained off fluid should be routinely inspected for sign of scorching and eventual debris - it may give a clue to the noise…

As said; there should be no mechanical noises in the box - sometimes loose rivets on the flex plate may rattle. In theory. worn-out band linings may grate, but normally one would expect metal to metal contact to cause slipping.

I think the focus should initially be at the downshift cable, if frayed it should really be changed - and the pressure/adjustment checks…

Frank
xj6 85 Sov Europe (UK/NZ)
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5

Thank you again. A pressure test will definitely help locate the problem. The stall speed is way too high as in the engine starts revving up in the low 2000s and continues.
No automatic downshift from 20 in high, no or not much slip except at full throttle, and mainly in 1st, also in 2nd. I’m not accustomed to auto boxes and attribute the rest to the torque converter, if it were engaged properly it’s quite driveable. No flare between shifts and shift quality is soft, but clean; If anything, far too early (As specified for roll-out). From a standstill it’s always in 1st and going fast worked well before I figured there was a bigger issue.

Because pan removal is in order I will be doing that on Tuesday afternoon. Fluid, filter, gasket, cable, band adjustment. Today the spare BW65 will have its internals inspected, so I get an idea of how it all goes together, what to expect and whether to get help. (Are 66 and 65 valve blocks interchangeable? Besides the filter spacer no differences are noted… Just in case).

After that, the pressure test for which I will have to source the correct adapter (would it be theoretically possible to, say, adjust the box a slight bit on the harsh side per the given gap at the valve body and drive it to a transmission shop? As long as there’s no slip and driving style is adjusted accordingly I can’t see how the box could eat itself up thusly, provided of course that the shifts are not too hard?).

While I have the service manual, exploded drawings and a general understanding, etc. I still have a unusually hard time in figuring out how it all goes together each time I have a look!

I can already see myself deconstructing the valve body, but hope for the best as per your instructions. Tuesday will tell.

David

6

The adaptor is quite possibly the same as the BW8, which is… 1/8" 27 pipe thread, male, with barb outlet fitting

I made a gauge with Ebay 0-230psi gauge, and 2m hydraulic hose, so I could drive around and test my setup after engine change, (and some trans work)…its fairly important imo to establish pressure before dismantle

The valve body is easy to remove and work on, but a last resort, if you do, take vids and MANY pics

7

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Since you are unfamiliar with auto characteristics; there should be no internal slip in the box - such slip will be in the bands and clutches. and band adjustments are called for as the first step…

However there is always some slip in the fluid converter under load; the engine rotor input runs faster than the input to the gearbox. It’s like a slipping clutch, necessary to allow the engine to run with the vehicle stationary in gear. The box always starts of in first gear, and like a manual driver shifts through the gears depending on speed and power required…

A brisk take off with lots of pedal is initially like a ‘mini’ stall test; the engine is trying to accelerate a 2 ton car - lots of converter slip while the car gathers speed, but rpms should not(!) initially exceed stall speed rpms. High revs is maintained, and climbs as car gather speed allowing the engine to run faster.

The slip reflects the difference between engine generated power and the power at the rear wheels. In principle, the slip can be detected by the difference between the speedometer and tacho reading in respective gears - ‘impossible’ during acceleration. In manual boxes there is no slip.

To detect the difference between unwanted slipping bands and necessary converter slip is complicated. Commonly, if engine flares up during upshifts instead of dropping quickly some 500 rpms; it signifies band/clutch slipping. And band slipping during cruising is detectable by higher rpms than ‘natural’ for the speed and gear. It’s sometimes more a ‘feel’ than science…:slight_smile:

Without pedal position information (by the downshift cable), the box assumes the pedal is to ‘idle’ or ‘light throttle’ and shifts accordingly - rapidly upshifting. I don’t know if downshift cable faults, no pedal information, influences stall speed. In theory it should not, but nevertheless the cable anomaly should be solved - otherwise the box will misbehave.

Don’t positively know if the BW65 and BW66 valve bodies are physically interchangeable, but odds are they are…

Frank
xj6 85 Sov Europe (UK/NZ)
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8

Thank you Tony,

Tony: I made a gauge with Ebay 0-230psi gauge, and 2m hydraulic hose, so I could drive around and test my setup after engine change, (and some trans work)…its fairly important imo to establish pressure before dismantle

This is a great idea. I’ll find out about the adaptor,; I disassembled the valve body of the bw65 yesterday, indeed very easy to work on, I was pleasantly surprised and also in awe of the complexity. It’s good to have something to look at, also I dare say that I feel up to the task. What can go wrong always will, anyway, so let’s get into it if not avoidable! Thanks a lot for looking it up.
The 65’s pressure takeoff plug was impossible to get out as I have apparently misplaced my right size socket. Also, how is one supposed to tighten the band adjuster locknuts? They are pretty tight and it is impossible to remove them with spanners-so how to keep the bolt from rotating when tightening?

Frank: I can’t feel any slip apart from the converter slip, the principle of which I do understand. It’s somewhat similar to lifting the foot on the highway and seeing revs drop a bit, just more pronounced whereas band/clutch slip will manifest mostly in torque transitions, I think, and via feel, so to speak :slightly_smiling_face:

If line pressure is lower, bands might be tightened insufficiently- no downshift cable, less pressure, less engagement… my guess.

Interchangeability will be reported if I have to remove my valve body, if only for somebody else in the future. We’ll find out tomorrow, and it’s probably just a fault with the downshift cable or the valve block being full of crud - I never had a look inside so far. So no need to speculate for now, I have a few good points to look out for and hope for the best.

Oh, and one last question: On older BW transmissions it was possible to set the pressure via a given gap at the downshift cam. I can see a way of conveniently measuring a gap there, wouldn’t that be precisely what the ferrule is for at the other end? (Yes, I understand that pressure is different, but it would be a good starting point for a cable of unknown length, and immune to stretch, but not individually correct). The cam is very steep for the first degrees which is why adjustments are so sensitive.
That gap however would probably have to be different between catalyst and open engines as there is quite a difference in power? Just mere speculation.

David

9

without refering to my manuals, I think the BW65/66 are aluminium case versions of the earlier trans,
so principles should be the same…the locknuts want soaking with penetrant.

Your symptoms indicate some pressure issue,
I would be investigating this, my custom auto trans gauge cost ~$30, most expensive part was hydraulic hose, but EFI fuel line should be ok

dont let it touch the exhaust!

I found my trans was very sensitive to any dysfunction of the throttle/kickdown cable, as that controls pressure in BW8, check your manual to see if it has a pressure chart (should have)

it is possible to assemble the valve body with parts not correcttly oriented, take MANY pics

10

Tony,

yes, the transmissions are related but there have been many changes. 66 is a revised version of 65 of course, both aluminium. 8, 12, 35 are different in a few ways; valve bodies look vastly different, there were vacuum throttle valves, electronic solenoids and so on, but I think gearsets were more closely related; band adjustments are different too as per haynes iirc. But still, principles are similar and pressure certainly just as important as with yours! Reassuring to know it’s that sensitive.
The whole transmission has been soaked from the outside in penetrant for protection and to help cleaning and dismantling. Still very tight though, getting lose is not a problem but tightening with a nut (edit: eh, a nut with a socket) while gripping the bolt…?

Efi hose is a good idea as well, and I have lots. A makeshift adaptor should do the job, after all I have a spare plug and can improvise, better than to wait for shipping. I’m also for the pressure theory, we’ll find out tomorrow (it’s half past midnight for me) and I can’t wait.
My bet is on the throttle valve because the cam moves without changing anything in behavior. Tomorrow will tell.
I have two pressure values which should be sufficient.

The way I dismantle parts is that I take pictures before disassembly and then lay them out in the order they were in - then pictures - then try to get it all back together quickly before the inevitable details that are never to be found in the 200+ pictures slip my mind! And in severe cases sketches as well. Screws and bolts back into their threads asap. I remember a friend and me dismantling an BMW engine, losing track because while I replaced most, he didn’t… so I stuck with it.

Until tomorrow, David

11

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There is no ‘gap’ adjustment of the downshift cable to cam adjustment on the BW65/66, David…

…instead the initial cable adjustment prescribes using the cable adjuster so the cam just touches the valve. The pressure checks and further adjustment is still required to fine tune the pressures to suit the engine generating pressure to the box’s requirements.

There is no principle differences between the catalyst/non-catalyst engines downshift cable adjustments. The adjustments compensates for eventual differences in engine/pump - tuning the box to engine performance. The shift points are ‘fixed’ by the springs in the valve body; varying the springs can be done to mate the box to different engines’ characteristics like torque and power curves…

Very courageous to dismantle the valve body without the appropriate manual - to absolutely ensure that all parts go back to their rightful places. Also, the manual describes the various springs’ characteristics - which seldom cause noticeable problems. Another point of valve body inspection is to ensure that the bores of the spool valves for wear - which may cause shift problems due to leaks. And scrupulous cleanliness and coupious use of hydraulic fluid for cleaning and initial lubrication…:slight_smile:

That you do not notice any slips beyond the normal ones in the converter is a good sign. But the very high stall speed is sort of worrying…

Frank
xj6 85 Sov Europe (UK/NZ)
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12

I was talking about a gap here or there. Just as starting point.

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As you can see, the cam will always touch the valve, but I will set the slightest gap as the pressure with cable disconnected is too low. Is that what you mean? Pressure is of course more individual so it won’t be too much of a help, but what works for the 35F should work for the 66?

In fact, all the haynes manual says in case the crimp stop has moved is:
“When a pressure gauge is not available (for me - I want a base setting) (remove oil pan, inevitably needed) …the cable (can be) adjusted to provide downshift cam settings as shown in the diagrams”
and the diagram shows nothing but the kickdown notch being fully engaged in position b and cam touching stop in position a, no gap. The Jaguar publication is silent on the topic but how am I to warm up the oil before pressure adjustment then?

Concerning the manual, I think I have all I need, service manual and parts diagram etc. included, listing springs, speeds, function etc. very nicely!

It’s not possible that my engine has magically gained a few extra horsepower by now and the box is overwhelmed, is it?:slightly_smiling_face:

Okay, I will have a look right now and report back tonight.
Wish me luck!

13

Forget about the BW35F theory. There was a huge gap at the cam even before I removed the wire. Cable was disconnected and slack in the engine bay; very weird! That cam moves freely and I am a bit confused.

IMG_6680
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I am very happy to report that there was no shmoo in the pan, the gasket fell off in one piece and the filter looks clean also (Per receipt, changed 2011).
Rear band seems to be fine, play is similar to the other transmission’s.
I will now look for a tube to remove the clip-in downshift cable fitting and change them as soon as my fingers have thawed a bit.
The metalastics for the transmission mount have the consistency of a medium rare steak at best, clunking source! Replacement is imperative. I might continue tomorrow as it’s dark already.

David

14

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The cable must be connected up to the pedal linkages, David - and the pedal in the idle position…

The initial installation adjustment is to remove cable slack - without moving the cam. Ie, motion of the cam is an indicator that you are ‘au point’. As cable moves the cam during driving the cam acts on the downshift valve, varying pressures with pedal movement.

The adjustment proper is of course to use pressure readings; first idling the engine to verify pressures to spec, then increase idle with the pedal by 500 rpms, again verify pressure s to spec - stopping the engine to adjust cable, then repeat as required.

As pressure varies with the valves position on the cam, and the cam is profiled to give the appropriate pressure variations with pedal changes - the cable adjustment just puts the valve on right place on the cam curve. And you can see why the adjustment is very sensitive…

For obvious reason the cable installation is done on a cold engine/box. But during final adjustments the engine should be hot, to ensure ‘proper’ idle and engine performance. The temp of the box is not specifically mentioned, but you cannot warm up the engine without warming up the box - the main source of box heating is the slip in the converter. Besides, the valve body operates on pressure differences rather than absolute pressures - the box normally works perfectly irrespective of box temps…

It is unlikely that the installation procedure will give the proper box response, hence the finer adjustments using pressures. What the manual likely means is that this is a crude verification - the acceptable procedure if the ferrule is missing is to try incremental adjustments on the adjuster.

It’s odd that the manual doesn’t so say, but the incremental adjustment is only relevant for minor shift anomalies. For faults like you experienced, it’s likely considered important to check things at the box end first…?

And, no, David - there is limited chance that the xk can overwhelm the box, but they did select a different box for the V12…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
**

15

during my research and adjustments (on BW8) I found out a few things

the pressure situation is that whilst initial adjustment must be precise, once significant load is applied the pressure shoots up very rapidly indeed…so basically, you dont want big pressure at idle, but after ~@1500rpm its near linear max

whining is not a good sound coming from an auto trans and is consistent with oil pump or thrust washer wear

the main failure items in these trans is the oil pump, front drum and front band, and torque convertor

These are all located at the front of the trans, require complete dismantle, and and very close examination to ascertain condition

the drum is subject to wear caused by internal rings similar to piston rings, and cannot be re-conditioned

16

You can buy an ATSG manual for the BW 65/66 for $5.99.

http://www.ucanfixit.ca/index.php/browsemanuals/product/1070-bw65-bw66-borg-warner-transmission-repair-manual-atsg

Pete

17

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The measured pressure is associated with engine rpms, Tony - modified by the valve’s position on the cam…

The varying pressure is the redistributed inside the valve body and further modified by the governor to operate the valves and the actuators for the clutches and bands. As you say; if the cam/valve position is incorrectly adjusted the pressures will be wrong throughout pedal variations, and the box will not shift properly…

Frank
xj6 85 Sov Europe (UK/NZ)
**

18

Pete, thank you very much for the link, I will go into that if I feel that I need it; I understand that it is an instant download, very nice! Also I know now that the 65 has been in some BMWs as well which might prove helpful. A lucky neighbour has a 3.0 CSi automatic iirc and I might be very lucky just in case?

Tony, the cam profile seems to hint at that. The whining is only in first and I’m not too worried yet. Also it’s not too bad, I reckon it’s fine.

The Pump provides pressure according to engine speed. The Governor changes output pressure according to road speed. The Downshift Cam Valve varies the pressure against the Governor’s pressure and as such we have RPM data being modified via speed and torque information. Said pressure then continues through the selector valves on to the shift valves - against spring pressure, continuing to activate bands and clutches. The flow then exhausts via the converter which, well, converts rpm to torque in given situations with stator and so on. How all the switching works out in detail is out of my picture but that should be the general idea… At least something like that, not magic but close.
My cam position thing however can be found on youtube! This is from “xj jesse” and his car runs fine yet the cam is pulled out just the same? that looks like some adjustment travel from slack…

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It was too dark and cold for me the last few days; winter sucks, right? But tomorrow will see me under there again, to the continuing amazement of my neighbours because I can spend that much time with the old Jag. I still think it’s the downshift cable or related and hope to be able to tell you tomorrow. If then possible, I’ll then drive to a warmer garage and do fine tuning, change the mount metalastics and some minor stuff. I will check shift points with tyres jacked up to be a bit safer before driving around.

David

19

David,

I’d be surprised if BMW used BW boxes. A very quick search seems to indicate ZF automatic gearbox. But it’s nice to look under a CSI hood anyhow …

Good luck on your search!

Jochen
75 XJ6L 4.2 auto (UK spec.)

20

As an update:

Today, despite it being a Sunday (gasp!) I crawled under the patient. It was raining cats and dogs but I managed to R&R the cable, adjusted it so it just came off of the stop, took a good look at all linkages and put everything back together. If it stops raining anytime soon I will resolder the horrible mess that the wiring under the starter relay is (I removed the relays for access), fill the transmission and start the engine to see if I made any progress; if not I will drive to a lift where it’s warm, safe, dry and accessible… look for pressures and if needed drop the pan again and change the valve body to have a look at both, and also re-read the thread of course. They look very much identical, by the way.

So for now thank all of you so much for your help, as I am immensely thankful!

David