Hi everyone, especially @awg since you have the helpful info I could find here, especially the Studebaker site:
I‘m replacing a leaking selector shaft seal on my BW8, and while in there I‘ll wash the filter out and replace the selector shaft seal and the front and rear seals (which were fine so far but cheap enough). Also, front and rear bands will be adjusted.
So far so good. Is there anything else I might want to look into, like band and drum wear? Can I inspect that?
I‘m not willing to disassemble it any further since it has low miles (45000) and shifted nicely on the test stand. The engine was seized for several decades but all the rubber and internals are still good. I believe there was an O-ring at the tach drive to change so if there’s anything worth having a look at I‘d like to know before it’s in the car.
Yes I have transmission on the bench upside down. I‘ll have a look at the band lining and whether it looks ‚thin‘ but it shouldn’t be and the rear band adjustment was very close. I won‘t have to worry about anything else, then, which is great. Reassembly by the book and as clean as I can.
I think I will do well with the spring and ball, not sure yet what I need to observe regarding the parking pawl. It seems to engage as it should. Will find out. I’ll make a tool to hold down the ball, maybe try a steel ruler or a similar thin strip with a 2-3mm hole in it bent to suit. Gaskets were in the mail today and the selector seal is much better, a little tighter around the shaft.
Thank you for the response.
Use a 7/8" (I think) spanner to move the detent lever just past the “max” position
that allows the ball & spring to just be placed in, then let the tension off the spanner…I think you will see what I mean when you do it. Easier than doing it under the car!
good man, mine wont kickdown, nor will most, some apparently will
I have been right thru the valve body and there is no fault within it
A vastly experienced trans rebuilder advised me to try a valve body swap, (it was altered several times during production)
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The whole point of an automatic is that it shifts down ‘on demand’, David - by throttle pedal movement…
Under light throttle the 66 upshifts to 3rd a some 20 mph, and toddling along at that speed; it should downshift at some throttle input. The faster you go the more pedal is required for downshift, and flooring the pedal is required a high speed - but above some 75 mph it will not downshift.
Different transmissions may have different shift speed, but even a kick-down would not downshift at some rod speed. An automatic simulates what a ‘manual’ driver would do, downshifting, when more power is needed, raising rpms, but even a rash ‘manual’ driver will avoid downshifting at high speed to avoid over-reving the engine…
An automatic that does’n downshift with throttle input at ‘moderate’ speeds, with adequate throttle input, is malfunctioning. It should not require flooring the pedal…so…?
Frank, no point in discussing this now, let’s see how it drives.
The kickdown cam is similar to the 65/66 in that the cam has some extra push (orange bracket) to open the throttle valve even further for the last bit of travel. This should ensure a kickdown at the relevant speeds if is all set correctly. But it seems that for some these transmissions do not do that correctly no matter what the setting is.
So it should definitely downshift at some point, and more likely so when wide open. The question is why many that are set correctly do not do that.
I’ll put it back together later today.
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The question is, David - are they indeed set correctly…?
The profile of the shift cam is designed to regulate the shift valve for shifting gear, up and down, at any appropriate combination of rpms, road speed and pedal position - kick-down is just an extreme pedal position.
Being operated by hydraulic pressures, the down-shift cable should be adjusted using pressure gauges - and the adjustment is very sensitive. The box will select gears for optimum engine performance compliant with driver’s intention (though with only 3 gears full satisfaction is not granted) - and pedal position is the only thing under driver’s control. Then there is the vital input from the governor, and indeed the valve body itself. Any malfunction in any of the above, and the box will malfunction - one way or another…
That fault rectification may be complicated is an understatement, but as designed; the box should function flawlessly - like mine…
You probably used this site as a guide to assembly, it really is useful
Its critical to replace the front seal that seals the torque convertor, and you should measure the bush while you have it out, also measure for endplay as described
I also replaced the rear seal, and their is some arrangement for the speedo cable, which is wise to attend, an o-ring I think
There is an o ring at the speedo cable as well as a very small lip seal, the o ring is as soft and smooth as a new one would be so I decided to leave that in place; I’m having a little trouble with the front seal which buckled and I do not know why yet. Went in straight on the press. Bit frustrating.
Endplay seems fine and I like the rear seal that’s in it with the extra felt, I will probably replace it but that is pending the front seal installation, I could do the rear later should it ever leak, but the front seal has to be right.
If you mean the bushing at the stator splines, that seems to be in good condition.
I know how it all works, and I winged the adjustment on my S3 with the BW66 that works exactly as it should, and verified it with a pressure gauge too. I know it’s critical: We’re talking about a different design here and many seem to have no kickdown despite everything else working nicely, so I will keep it in mind when driving. It doesn’t improve when the extra step on the cam is fully engaged on full throttle as it has to be.
What I can offer is a lack of pressure leading to this since more throttle means higher shift pressures. If the maximum pressure doesn’t reach its design value it will be less likely to switch to a lower gear.
If that is weakening springs in the pressure regulator, the governor or general leakage past the valves and actuators increasing over time I don’t know.
The throttle valve always limits the pressure that goes to the valves which decide what gear to use, so a limited peak pressure will show in a lack of kickdown when that valve sends the full pressure, my theory.
I have bought the wrong front seal (for AOD, C3…). The correct one is about a millimeter smaller in diameter and is already in the mail.
As I said the wrong one went in straight and buckled, I had a feeling it might be too large but what do I know!
I presume you are talking about the front oil seal
When I dismantled a BW8 and a BW12, I found the oil pump shaft to be .020" greater in diameter on a BW12. There was no other way to distinguish the entire oil pump
Lack of kick-down cannot reasonably be regarded as a ‘65/66’ design flaw, David…?
Lack of pressure is, as you say, a viable explanation. And over time the engine driven pump lose efficiency and the pressure regulators may drift off. And indeed; bore wear in the valve body will occur over time - and the governor may no longer be up to scratch. All may contribute to loss of kick-down - which of course will only be noticeable at high speeds. At other speeds the lack of kick-down is masked by the normal shift actions?
One possible test; cruising at, say 30 mph - flooring the pedal should kick down from 3rd to 1st. Normal shifting with pedal use would only go from 3rd to 2nd…
It will be interesting when David gets this trans in,
I am not 100% sure, but presume it hasnt been used yet in his vehicle
Its a strange thing, nothing at all will induce mine to kickdown, although it downshifts and upshifts perfectly as it should, line pressure is tested to be good, and the adjustment is correct, as per FSM, and verified correct pressure
I have verified by adjusting the trans over its entire range that the kickdown valve is engaged, as it is manual, via cam, as per Davids pic.
(You cannot use the vehicle with line pressure adjusted too high or low)
That cable is the only adjustment ( a pressure gauge is very useful)
looking in the FSM, the action within the valve body to achieve kickdown;
"line pressure…hits the relevant… shift valve, and that, in combination with spring pressure is sufficient to overcome governor pressure "
Because my trans otherwise shifts at the correct speeds and pressures, I do not see how my governor could be faulty.
That leaves the springs
additional spring pressure would add to control pressure to overcome governor pressure
I do not know where you would obtain stronger springs for those 2 valves to conduct this experiment. I do have a complete valve body, so I can have a look at the relevant springs
I haven’t considered this, I will slide the new seal over the torque converter / oil pump drive before I hammer it in, good idea
My engine broke down maybe in 1977 maybe later, the head was in the boot, low mileage and frequent service from the oil change tags I found in the mouse nest.
So I don’t know how it will drive, yet. Only verified that the transmission goes through all gears on the test run and found the leak. All the rubber in the car looks almost like new
If the line pressure is correct and the valve goes through the full range it can only be weakening springs (I don’t think they would, but what do I know!), or a loss in peak pressure since kickdown should happen with shift pressure at its highest. If the valve never sees that pressure it won’t shift down or it won’t shift down as often, but the lower pressure functions will work perfectly. Then again the governor peak pressure would stay high since if it would drop, the kickdown would work again. Very strange all this. I’ll find out if it all works say in March or April.
I agree from the detailed FSM description of how it works that loss of pressure within the trans due to worn internal seal rings may be a possibility to.
Even though mine measured within range, as I recall, it was slightly (less than 10%) below max pressures shown in manual
We know of past experience of lister Hoff ?, who even had his BW8 rebuilt, but ended swapping to a manual, as he could never overcome this issue
The BW8 valve body is a strangely ancient design, same as '51 Fordomatic
No one left around who knows about them. My informant did his apprenticeship on BW trans, and advised me this was a known issue, and a valve body change was the cure as he recalled. I do have a couple of spare BW8, so I could try that.
Maybe when I do my custom exhaust, the present one prevents easy pan drops
In a 420G, you cannot remove the trans without also removing engine
I know I did remove the BW12 from my S2 XJ with engine in place
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After a lot of thinking, Tony - what do you actually consider a ‘kick-down’…? Or put another way; what is the perceived difference between a ‘kick-down’ and a ‘downshift’…?
I’m not even sure any longer that there is a specific ‘kick-down’ function on the box - with the pedal floored; speed related upshifts and downshifts mirrors the specified shiftpoints. Ie; if the shift points are to spec the box works to spec - deviations then relates to the possible faults mentioned…?
the same as I expect on any other 3 or 4 speed auto trans I have driven,
and as described in very great detail in the FSM
To sum up, a kickdown ( to a lower gear) takes place with heavy throttle input and increased speed, and downshift upon reduced throttle and reducing speed. Mine will do the latter perfectly, but never the former. It also upshifts as expected
We have heard from one BW8 owner who claims that his does have the kickdown function
It should be there, the mystery is why not, in the absence of any obvious fault.
The fact the BW12 went to a micro-switch activated kickdown system may be a clue they were not satisfied with the previous design
