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Old 04-04-2010, 08:56 AM
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TH 400 front clutch engagment.

After looking at a lot of good information about rebuilding the TH 400, I have yet to find any information concerning diagnostics, what causes failures.
What I have is a burnded forward clutch that was caused by the clutch engaging with the shift selector in park at fast idle during cold start.
My question is: What sequence of the system would caused the clutch to engage with the transmission in park, then disengage after a short period, 2 minutes or less. This has me worried that installing a fresh rebuilt without knowing what the cause could result with the same problem.
I appreciate any information that could point me to the possible cause of this happening.
Mickey

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Old 04-04-2010, 09:34 AM
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Same answers apply that I provided earlier in different thread.

Low fluid , hard seals, sealing ring area worn , cross leaks, linkage mis adjustment could cause a forward clutch pack failure.

the clutch pack may have been on it's way out due to age and the pack finally was stuck together while the trans was in park.

I would suggest a proper rebuild by a knowledgeable person to avoid the problems you worry about. If you do not have the knowledge , experience and machines to check clearances or re-machine the parts, you may have another failure if the problem is not seen by the novice eyes

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Old 04-04-2010, 10:28 AM
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Quote:
Originally Posted by Crosley
Same answers apply that I provided earlier in different thread.

Low fluid , hard seals, sealing ring area worn , cross leaks, linkage mis adjustment could cause a forward clutch pack failure.

the clutch pack may have been on it's way out due to age and the pack finally was stuck together while the trans was in park.

I would suggest a proper rebuild by a knowledgeable person to avoid the problems you worry about. If you do not have the knowledge , experience and machines to check clearances or re-machine the parts, you may have another failure if the problem is not seen by the novice eyes

Thanks again for the reply.
Never low on fluid, seals not hard or damaged, sealing rind area not damaged or worn, linkage was properly adjusted, about cross leaks, could a missing inner seal cause a cross leak?
I know what caused the failure, "High idle in park with clutch engaged" what I would like to find out is: what caused the clutch to engage with the selector in park keeping the vehicle from moving and the clutch to heat and burn up. The clutch did disengauge after a short time and that could be noticed by the engine rpm increase.
(a proper rebuild by a knowledgeable person) A person has to find a "knowledgeable person" and that requires some knowledge to recognize a "knowledgeable person".
Thanks,
Mickey
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Old 04-04-2010, 11:00 AM
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Quote:
Originally Posted by soBit
Thanks again for the reply.
Never low on fluid, seals not hard or damaged, sealing rind area not damaged or worn, linkage was properly adjusted, about cross leaks, could a missing inner seal cause a cross leak?
I know what caused the failure, "High idle in park with clutch engaged" what I would like to find out is: what caused the clutch to engage with the selector in park keeping the vehicle from moving and the clutch to heat and burn up. The clutch did disengauge after a short time and that could be noticed by the engine rpm increase.
(a proper rebuild by a knowledgeable person) A person has to find a "knowledgeable person" and that requires some knowledge to recognize a "knowledgeable person".
Thanks,
Mickey

When the manual shaft is in the park position the fluid is exhausted , not supplied to the forward or any clutch in the t-400. Hence my speculation of the cross leak.

As I pointed out in the other thread , the center lip seal on the forward clutch only slows the apply of the clutch.

Since you are learning here........ look at the forward drum again. there is only one way for the fluid to get in and one way out via the check ball assembly in the drum or the piston. Which this subject brings up another item I automaticaly look at... the forward drum must have a check ball in the complete assembly. This would be a check ball in the drum or in the piston. This vents off residual fluid in the drum when not applied

I would wonder if the engine was running poorly till it built up some heat and then RPM picked up giving the illusion the trans was at fault... in a gear when it should not be?

Experienced trans person would be in a shop that has recommendations from your friends.

With out the proper knowledge and tools , you are possibly destined to repeat the failure in the trans. Trans failures can be expensive 2 or 3 times around.

Since you are disabled , spend your money wisely when possible = which is something you are aware of, I am sure

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Old 04-04-2010, 12:16 PM
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Quote:
Originally Posted by Crosley
When the manual shaft is in the park position the fluid is exhausted , not supplied to the forward or any clutch in the t-400. Hence my speculation of the cross leak.

As I pointed out in the other thread , the center lip seal on the forward clutch only slows the apply of the clutch.

Since you are learning here........ look at the forward drum again. there is only one way for the fluid to get in and one way out via the check ball assembly in the drum or the piston. Which this subject brings up another item I automaticaly look at... the forward drum must have a check ball in the complete assembly. This would be a check ball in the drum or in the piston. This vents off residual fluid in the drum when not applied

I would wonder if the engine was running poorly till it built up some heat and then RPM picked up giving the illusion the trans was at fault... in a gear when it should not be?

Experienced trans person would be in a shop that has recommendations from your friends.

With out the proper knowledge and tools , you are possibly destined to repeat the failure in the trans. Trans failures can be expensive 2 or 3 times around.

Since you are disabled , spend your money wisely when possible = which is something you are aware of, I am sure

Thanks again, I really appreciate you're answers in the way you question different possibilities being misinterpreted as something else.
Ex: poorly running engine interpreted as tranny fault.
The poorly running engine was part of the problem, it was overly rich due to choke adjustment, requiring part throttle to keep it from stalling until the choke opened. the increase in RPM was felt when the clutch disengauged and the free running of the engine allowing good trottle response and higher rpm which was not possible with the clutch engauged.
The forward drum checkball has been varifed.
I believe the cold fluid, for some reason, caused the clutch to engage until it warmed up at which point allowed clutch to disengage.
That is what I have questions about.
I also apreciate the mention of cost/spending wisely.
About experienced shop/person: Years ago a co-worker had his Eldorado towed to a transmission shop when it stopped on him. The shop looked at it and told him he needed the tranny rebuilt, around 1500.00 dollars if I remember right. The car was not old and I doubted it needed to be rebuilt. I asked him exactly what it did/acted and his response was it starte,runs fine but doesn't move at all in any gear. I asked if his speedometer worked, he said yes. Next question was have you worked on any part of the wheels, axles recently, he said he had replaced CV joint booth. I told him to look in that area for problem. Next day he drove his car to work, all smiles he came to me and said, cost me 6 dollars and change to fix, I hadn't tightened the bolts on the axle and they fell out, new bolts took care of it.
Spending wisely and and getting educated detailed quotes are a must, that's why I ask so many questions.
Thanks again,
(I did rebuild the trann in my daughter's 4X4 explorer last year, still fine after some 30,000 miles)
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