transmission

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Apr 25, 2005 | 07:36 PM

#16

jakemahn

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Transmission

Has anyone heard of servos being damage due to extreme heat from the exhaust. I was told that a flaw (one of many) in the a4ld is that the exhaust heats up and heats the tranny. The assembly of parts including the overdrive servo get damaged and actually harden. Then the shift from 3-4 does not occur and the servos need replacing. Thoughts?

Apr 25, 2005 | 10:20 PM

#17

mrshorty

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From: UT

I can't say that I've heard of that as a common failure mode for the 3-4 shift in the A4LD, but I won't say it's impossible either. Did they suggest a way to diagnose?

Apr 27, 2005 | 06:21 PM

#18

jakemahn

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transmission

It was said that the exhaust must be removed and pan dropped. The servos are then assessed for hardening. This means that they become too rigid to function properly. I can only assume that the assembly that contains the servos would be removed down to each servo and then checked for proper functioning. Since I have never seen a servo, I am not completely sure what "functioning" entails. In the ATSG A4LD manual, I can see the diagram that shows the overdrive servo. There are several springs with a corresponding accumulator valve(intermediate, overdrive and 3-4 backout valves). I am unable to see how the valve functions even with this book. I will call the place and try to get more info.

Apr 28, 2005 | 11:29 AM

#19

lwcassady

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I'll throw my 2 cents' worth in (probably actually worth less that 1 cent, though). First, I must add the disclaimer that I know next to nothing about transmissions, but when talking to a friend of mine about my A4LD, he relayed to me a story of when he rebuilt his. There was one seal that must be frozen before you put it in because it will be damaged if you put it in at normal temperatures and will not seal well. This seal apparently expands and contracts quite a bit with temperature. The transmission failure from this mistake was immediate, though, and it affected only Reverse. I don't know if this applies, but maybe something similar could be the culprit and someone may get an idea from this since you said that it had been rebuilt "recently" (19,000 miles ago).