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Re: 1992 V6sei auto gearbox repair

Posted: Mon Jun 11, 2018 2:44 pm
by xantia_v6
Bad luck. It does sound like a lack of system pressure, maybe a seal has not been seated properly, causing a significant internal leak.
I don't think it likely that you have done secondary damage, it takes quite a bit of heat to damage a clutch and the smell of thee fluid would have given it away.

Re: 1992 V6sei auto gearbox repair

Posted: Mon Jun 11, 2018 3:08 pm
by MTXM
That is helpful and encouraging advice Mike, but where do you think the seal might be located - not somewhere accessible like on the governor I suppose!! With regards, Matthew T.

Re: 1992 V6sei auto gearbox repair

Posted: Mon Jun 11, 2018 5:16 pm
by xantia_v6
I don't know these transmissions well enough to suggest a particular seal.

Re: 1992 V6sei auto gearbox repair

Posted: Mon Jun 11, 2018 6:26 pm
by MTXM
Many thanks Mike and perhaps Dean may have some ideas. I have had governor seals fail before that have caused weird changes in forward drive and loss of reverse. It would probably be worth my while pulling the governor before removing the box as I did before in addition to checking the valve block. I guess the other possibility for low pressure is a faulty pump, although the original pump was found worn and replaced. With regards, Matthew T.

Re: 1992 V6sei auto gearbox repair

Posted: Mon Jun 11, 2018 10:27 pm
by Dean
Well, that well and truly peed all over your bonfire of success didn't it😞

I personally would doubt the governor is at fault in this case, the fluid pressure at each stage of the governed is a signal to the valve block and 'leaks' as a function of its operation, this allows the valve block to determine road speed by the pressure in these lines and the engine torque sensor (kick down) shift accordingly so if this signal was incorrect due to blown seals you might loose reverse, a 1-2, 2-3 or 3-4 shift but it cannot create a clutch slip, this can only be low line pressure, clutch Pistons or anything on that side of the system.

Of course I am not a professional but my guess would be there is a problem with the pump, pickup, filter, clutch pack or the pressure regulating stage of the valve block, granted that's 80% of the gearbox but it would be my guess. It looks like the original problem has not been resolved.

See what the specialist says but if the fluid is darkening already, after a full strip and clean then there is slippage of the clutches and you should not drive the car until they have looked at it.

Keep your chin up Matthew!

D

Re: 1992 V6sei auto gearbox repair

Posted: Tue Jun 12, 2018 11:43 am
by Dieselman
I would have thought leaking governor seals might cause the problem due to reducing hydraulic pressure, but the randomness of the behaviour doesn't fit with that.

I wouldn't open the box in any way unless the rebuilder gives you permission to do that. The last thing you want is them to say the warranty is void as a result of you opening the box.
They charged you for a complete rebuild and setup, so ultimately, it's their problem.

Re: 1992 V6sei auto gearbox repair

Posted: Tue Jun 12, 2018 4:59 pm
by Dean
The governor is supplied with a regulated flow of fluid from the top pressure and distrbution regulating part of the valve block, you should (in theory) be able to remove the governor but still have sufficient pressure on the actuator side of the hydraulic system to operate the clutch packs and supply the torque converter, dont forget the governor works by valves operating with centrifugal force against callibrated spring pressure and when stroked exhaust oil into the governor bore which flows back via the transfer gear case and differential houseings supplying that area with oil.

This is why reverse is often lost, the lightest spring loaded valve controls the reverse inhibitor to stop you selecting reverse while travelling forward, when the seal fails fluid leaks away which the hydraulic brain sees as forward motion (an open valve) , therfore inhibiting reverse gear selection, obviosly there are other issues that can cause this.

I would advise the same, dont drive, dont touch and speak to them (as you have) but your symptoms are the same as described by the previous owner, therefore the root problem may not have been fix, they have fixed the effects of the problem but not the cause.

Good luck Matthew.

Re: 1992 V6sei auto gearbox repair

Posted: Tue Jun 12, 2018 7:21 pm
by MTXM
Many thanks for your helpful comments and sympathies chaps and I have no plans to carry out any further work on the box, apart from removal with the engine, when time and energy and enthusiasm permit! Given the symptoms experienced I had hoped that a change of valve-block would resolve matters, but sadly not. I note that broken governor seals are unlikely to cause clutch slippage, even after the strain of pulling away using incorrect gears.

After securing this advice my next task is a further conversation with the garage, who do seem happy to recheck the box, despite my input! My main concern at the moment is not so much the further removal, but whether the box will work next time and I guess there is no way of testing before installation? Another option may be to have a light refurbishment and checks carried on my other working box.

All I know about the previous problem was that the t/c apparently failed and after the first rebuild forward drive was then lost. During the latest strip down the pump and clutches were found to be worn. On this occasion I do have both forward and reverse gears, although the gears were incorrectly selected and changes erractic with no fourth gear present and then the slippage developed.

I shall keep you posted on progress and many thanks again.

With regards,

Matthew T.

Re: 1992 V6sei auto gearbox repair

Posted: Tue Jun 12, 2018 7:29 pm
by MTXM
After looking back at your earlier advice Dean, I think I may possibly have lost both 1-2 and 3-4 gear changes, so could faulty governor seals then be involved? If the box was only operating 2-3 gears, over time might not the strain of pulling away in second also eventually lead to clutch slippage? In response to Will's earlier comments the behaviour of the gears was not so much 'random' than 'restricted'! With regards, Matthew T.

Re: 1992 V6sei auto gearbox repair

Posted: Tue Jun 12, 2018 9:18 pm
by Dean
In all honesty, if any of us knew the in's and outs of auto gearboxes we would rebuild them for a living! I can only guess based on my very limited knowledge but it s the slipping that bugs me and if it were me having rebuilt the box I would be looking at the oil pump.

If you have swapped the whole valve block out with no change and it was a shift problem I would be lookng at the governor purely because it's simple to get to and visually inspect but I doubt very much it is the problem.

My train of thought would be this, you have clutch slippage so on at least one clutch pack you have low pressure to the actuator, either due to supply or a failure within that clutch pack. Also though, a second issue of incorrect gear selection, this could be the brain (valve block) is not interpreting the information it receives correctly or the information (in the form of fluid pressure) is not correct and the brain is not making the right decision based on faulty information. These two faults are on different sides of the box, one on the decision making side of things and one on the work side. This could be two separate problems but my hunch would be that the issue lies upstream of these two systems, fluid pressure to various sub systems is regulated by a series of valves in the valve block which has been swapped so for the moment that can be discounted, the heart of the whole box is the oil pump and the main line pressure, while this is maintained by the valve block that isn't worth anything if the pump cannot supply pressure at the minimum required, if this is the case I would expect to see spurious faults all over the various systems.

One test I am aware of is to take a pressure reading at the two test ports on the gearbox housing, one is line pressure, the other is a test port that should show varying pressures depending on the gear selected which will tell you if oil pressure is a problem.

So far as bench testing goes I believe there is a manufacturer specific tool to which the valve block can be bolted to supply it with pressurisd fluid (a simulated oil pump) and check it is doing the right things in all the right places, this would be a specialist, manufacturer specific tool however. I am not aware of any further tests and certainly nothing to test a whole gearbox while on the bench so to speak.

Wills advise is the best, you should not be paying £1400 for a gearbox rebuild to have it come back with the same issue, I would expect a full rebuild kit for that, all new clutches and seals, throughout the box, however you did have a new pump which can't of been cheap.

Let them have it back to sort out, it is their job.

D