BW65 /66 gearbox in XJ6 Series 2

Hi Jag-Lovers
This is Wolfgang from Germany (please excuse my bad English), and to be honest: MeToo…
My infection with a Jaguar virus over 30 years, started with buying a XK140 in Boston (instead of an Etype).
Im a long time reader of jag-lovers, but now I´m registrated to ask something tecnical which i can´t solve myself, in Germany we do not really have specialists for BW Gearboxes…or i didn´t find them.
The story in short:
XJ6 series2 , engine (and gearbox) from Series3
I got the car to complete it, engine and gearbox were already mounted.
Driving was good, but the gearbox was very hard shifting. So we decided, to install an overhouled one, it was stored for a longer time, the workshop was sold and no information about this gear were available. Shifting is very smooth, quiet, gearchange correct, but the one big mistake is a high frequency weee noisy vibration and loss of friction when accelerating more than necessary from standing. Never in 2 or 3, never at higher speeds (20mls/h), when the critical moment is surmounted, the mistake will not occure until the next stop.
I made the mistake to fill Dexron II inside when mounting the new gear, but this is changed, new filling with ATF type F was 6L.
I guess, that the mistake comes from the front clutch, I´m not shure if the front clutch gets the old oil out and new in when operating or if a small oil volume gets only in and out when operating.
I also made a pressure gauge inside the car, the tv linkage ring mark adjustment fits not to the recommended oil pressures. Only incrasing the gap brings an increasing oil pressure at 1200 rpm.
Is it correct, that this pressure is just the pressure for the front clutch? it starts with 4,2 bar at idle speed in D, this seems not so much for the main clutch.
Thanks for any ideas in advance

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Welcome aboard Wolfgang. Good to see a new Jag driver in this country :slight_smile: I am sure more knowledgeable people will chime in and help you with the transmission.

@davidsxj6 may be your best bet: speaks German, and understands those transmissions.

Very flattering, Wiggles, thanks.

The transmission is very simple, in D you have three inputs to the valve body: input shaft speed, output shaft speed, throttle position.

Those three inputs reach the valve body and result in a hydraulic pressure that determines (springs, valves) which gear is appropriate and how hard the clutches and bands are applied by the servos.

In any other selector position the pressures are simply modified or redirected.

The servos don’t care what fluid is used as long as the viscosity roughly resembles ATF. So this is not your problem.
I‘ve used Dexron III which is too slippery, the transmission did not break down.
The only adjustment for the engagement of a gear is the band adjustment which is described in the workshop books.

The other important factor is the correct throttle cable setting. Fragile and important to get right. Don’t even look at the ferrule, set the pressure correctly to the specification and then do the test drive and verify that it shifts at the correct speeds/ loads. It should be set so that you can feel first gear engaging with a little jerk when coasting to a stop, perhaps slightly weaker but not too much or wear will increase a lot. Too strong (higher pressure) will result in harsh shifts at higher rpm than necessary. This setting affects the entire transmission in its entire operation. Maybe your cable is set too weak. Do you feel the kickdown detent?

If all that is done right and there is a whine in 2nd, 3rd and/ or N, or during the shifts, please record the noise and put it on youtube, and share here. A noise in 1st gear is normal.

It is possible that you have some valves sticking or that the cable is binding somewhere from your description.

Welcome aboard Wolfgang!

You’re right - there are no gearbox shops at any motor mile in our industrial areas. But what you describe doesn’t sound like a full-blown reconditioning of the gearbox.

Before you go into a gearbox exchange, do the simple things first: with a SIII power train you have a BW66 gearbox in your car. Get yourself the SIII Repair Operation Manual and perform all the tasks meticulously that are described there. It isn’t that much you can do, but oftentimes what you can do is sufficient: if you drop the pan you should be able to check the bands for excessive wear. Assuming they are still within specification you can and should adjust tension. Again, the specifications are in the ROM. Then refill with the correct fluid and to the correct level - the procedure is described in the ROM. Unfortunately, I only have got the ROM for SII (BW65); otherwise I’d pm you the chapter. If you can’t get hold of the SIII ROM pm me, as BW65 and 66 aren’t that different and any flickering torch is better than total darkness …

Good luck and keep us posted - don’t worry about language! This is a global list and not reserved to native English speakers.


75 XJ6L 4.2 auto (UK spec)

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Thanks for welcome and quick response, especially to you David.
Today I compared and measured the tv cables, there is just an offset of 5 or 6mm between two original looking cables between the ferrule and the joint bolt. but i did not compared the length of the joint, will do this tomorrow.
the distance to the ferrule was at the beginning fixed to 0.4mm accordung to the manual. But there was no increasing oil pressure at 1200 rpm.
Than I changed it to about 10 or 12mm, the sliding was less, shifting feels normal, just the oil pressure war better and the pressure test at 1200rpm was ok, 7 or 8 bar.
If i got it right from the manual, in D/1 just the front clutch and the one way clutch (bearing) are engaged. In “limited” 1 it is just the front clutch. So the band adjustment should not have any effect in this gear. My tests have shown, that the same slipping is in both positions. So I think it must be the clutch.
Or not? :thinking:

Get the cable adjusted correctly before further action. Depending on the year there might be another internal base adjustment that partially explains the variances in cable setting. Again, ignore the ferrule. If the pressure is too low the clutches will slip!

If you still have slippage with the cable (definitely) adjusted correctly, we can look into it further.

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Hello Jochen,
I saw your message after sending the upper one.
The manuals …I have them all I think, also I have repaired some gearboxes, but all GM.
For my opinion, the gearbox was really overhauled, because driving after or without that slip is fun. It looks very fine, without spray can. Gaskets looked correct, no silicone, but You are right: This is no proove. But I have never a 6cyl. Jaguar transmission driven shifting so smooth and quiet.
The point is: Before I open the box, I want to think and try and check all, I can do from outside.

Aye Aye Sir, I will notice the pressure at the exact revs. But the values at 1200 have a big range: 5,2 to 6,9 and at 750rpm 4,1 to 4,8.
I will do it again if the rain stops sometime (sounds like summertime).
But a question to all friends of hydraulic: Are these few bar the hole pressure to close the clutch? I would expect a lot of bars more, like 20 or 30.

You are right, maybe I have two types of gearboxes, carburetor 65 and injection 66, with different linkages and cable length.

I think so, keep in mind that the servos have some surface area.

If you have like 4.5 bar at idle, the problem is an internal one. You say that the transmission is incredibly smooth which worries me just a bit. Are all the shift points in the ballpark?

Also - I think the cam in the transmission is the same, so I believe it does not matter which manifold etc. you are using. Worth remembering for later troubleshooting.

A couple of points, Wolfgang. The purpose of the cable adjustment is to tune the gearbox to the engine output/rpms - the absolute pressures are therefore wide. The important point, with the pressures within tolerances, is the increase in pressures when rpms is increased by 500 rpms.

The difference between the two readings must be between 20 - 25 psi - the lower pressure not exceeding 75 psi. Ie, an increase of 500 rpms should give 20 - 25 psi higher pressure - the box reacts to difference in pressures as given by the engine…

The ferrule is crimped on at the correct position when adjustments are complete - as a downstream reference. With change of engine or gearbox it is not given that the ferrule position is correct - it’s the correct pressure adjustments that sets ferrule position, not the other way around

The front clutch is engaged in all forward gears, but the higher torque at take-off may cause clutch
slipping. And the lesser torque in higher gear and higher pressure with higher rpms may ‘hold’ - but generally; the internals in the box is dimensioned to give adequate pressures at the clutches bands at all times.

As the rear band is only applied in 1st and reverse; how sure are you that the rear band is correctly adjusted. And as the band linings are very thin they will wear out very quickly if slipping. And metal to metal contact will then certainly grate as band will easily slip when worn out.

I think the rear band is more suspect than the front clutch - only strip-down will tell in either case…

xj6 85 Sov Europe (UK/NZ)

I would suggest to make and fit an auto trans pressure gauge ( if possible)

This is hundreds of times easier and less expensive than removing the trans

It should operate in a range specified in the Service Manual

I did this for my BW8, I have not checked BW65 to see if it has a port, but I bet it does

0-300psi gauge, adaptor with barb, 2m of ATF hose

Good chance pressure is too low due to changed cable positions

Always a great idea, but I think that is exactly what he did.

A good point is that torque output might have changed slightly with his new setup. Enough to make such a difference? With the cable snapped the box still works okay, but slips and is very smooth, and shifts up quickly.

Yes, you are correct, seems he did, but the results are uncertain ?

quote from his 1st post, my bold

I also made a pressure gauge inside the car, the tv linkage ring mark adjustment fits not to the recommended oil pressures. Only incrasing the gap brings an increasing oil pressure at 1200 rpm.
Is it correct, that this pressure is just the pressure for the front clutch? it starts with 4,2 bar at idle speed in D, this seems not so much for the main clutch.

I think the gent mentioned he has the correct manuals, I am familiar with PSI, not bar

it never hurts to upload relevant FSM excerpts

One suggestion that may be helpful to the OP is use Google Translator as from what I have seen, it does a good job

It may be the pressure is correct, and some other fault is present, however, thats a nasty prospect, so I would want to be sure pressure was not the issue, insofar as I could

Maybe because I‘m German too but I have absolutely no trouble with his English, and doubt google can produce anything nearly as good; most likely worse.
I understand that the pressure was way low and if he increased the gap at the ferrule the pressure did go up, at elevated idle speed. In other words, as soon as he adjusts the pressure upwards it does exactly what it is supposed to do, it increases.

4.2 bar is ~ 60 psi, 14.5 psi per bar.

What he needs is 60-70 psi at idle and 75-100 psi 500 rpm above idle, at temperature in D. I would increase the pressure until he feels first gear engagement and see if it goes away, he is correct that his testing should rule out any band issues.

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Oh and by the way, ChatGPT can translate most things incredibly well, it even managed to translate the joke from this ad whereas all the more traditional digital translators failed. German to English I can assist if something is unclear…

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No offence to the OP, he said he had issues, his English is good, grammar and punctuation would likely be fixed, be easier, probably need it myself to fix up my crap answers :rofl:

The spring loaded spool valves in the valve body redistributes pressure to clutches and bands, David it’s the differences in pressures generated by engine, pedal position and governor that changes gears.

The cable adjustment just brings the pressures within the operating parameters of the box - which is set by the springs in the valve body. The cable adjustment is very sensitive - and important. If the spec pressures cannot be set with the cable adjustment; internal actions are required. The spec pressures are sufficient to operate box properly…

xj6 85 Sov Europe (UK/NZ)

I said this exactly…