AT Slips in D/2/3, but not in reverse???
07-28-2008, 09:21 PM
#16
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I have an '81 US 928 with automatic trans. Dr. Bob (what a great guy!) discovered my transmission was leaking fluid after I left him a sample on his spotless garage floor. I used uv dye for trans fluid and traced the leaks to cracked rubber hoses running to the cooler.
I had the hoses replaced using the original fittings at a great little hose shop in Glendale. I replaced filter, drained the converter, and jacked the front of the car up to do a "poorman's line flush" with the help of gravity. The old fluid was pretty tired, but no metal shavings.
I've checked the level on level ground (it looks level
), with the car running, cycled through the gears. I didn't have the emergency brake on I don't think. When I check the level, should the car be in Park or Neutral? The trans shifts into neutral and Reverse normally, but it is delayed to go into the drive gears.
I hope someone has some ideas, before I did the fluid change, it drove fine, never slipped.
I had the hoses replaced using the original fittings at a great little hose shop in Glendale. I replaced filter, drained the converter, and jacked the front of the car up to do a "poorman's line flush" with the help of gravity. The old fluid was pretty tired, but no metal shavings.
I've checked the level on level ground (it looks level
), with the car running, cycled through the gears. I didn't have the emergency brake on I don't think. When I check the level, should the car be in Park or Neutral? The trans shifts into neutral and Reverse normally, but it is delayed to go into the drive gears.I hope someone has some ideas, before I did the fluid change, it drove fine, never slipped.
A couple of possibilities, you had hoses made, shavings from the new hoses could have contaminated the valve body, causing a stuck valve. Fix, rebuilt VB.
Wrong filter installed, did you match the filters up, where they exactly the same, also the new filter could have a missing or damage seal, were it seal on the suction side of the VB. This may also be the cause of that noise, pump cavitations, sucking air.
Bill is right; the symptoms could also be a failed B2 piston, (big cover next to the fluid tank) which also happens in 3speed transmissions. Remove it and check piston for any Cracks.
08-06-2008, 07:43 PM
#17
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Steve,
Thanks so much!!!!! If I may ask you one question, how does the fluid circulate through the hoses to the cooler and back? In other words, what is pumping it through? I will check all that stuff.
Thanks so much!!!!! If I may ask you one question, how does the fluid circulate through the hoses to the cooler and back? In other words, what is pumping it through? I will check all that stuff.
08-06-2008, 08:23 PM
#18
Under the Lift
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There is only one ATF pump in the early trans. Since you have reverse, the pump is working. My very limited knowledge points to an area called the operation engagement accumulator, which operates when any forward gear is engaged regulating pressure flow the brake band B2. Something is blocked or jammed there. Hopefully Steve will have advice on whether this is likely the issue and how it might be cleared short of a rebuild.
08-09-2008, 01:44 PM
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Took out the filter and valve body, found several culprits. 1. When I installed the filter last month, I missed the old cork gasket that was stuck to the valve body, thinking back, it was not easy to get the filter in, now I know why.
# 2 the valve body was absolutely filthy with buildup, propbably due in part at least to the filter not being seated properly.
# 3 There is a 3 inch vacuum hose for pressure modulation I thing that was not attached.
Now that my whole valve body is apart, and cleaned, I notice that my Porsche manual doesn't cover the 3 spd auto in it!!
# 2 the valve body was absolutely filthy with buildup, propbably due in part at least to the filter not being seated properly.
# 3 There is a 3 inch vacuum hose for pressure modulation I thing that was not attached.
Now that my whole valve body is apart, and cleaned, I notice that my Porsche manual doesn't cover the 3 spd auto in it!!
Last edited by scott863; 08-10-2008 at 05:54 PM.
08-15-2008, 05:58 PM
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Jim from 928Intl was good enough to save my butt and refer me to Ted the Transmeister, who had my valve body cleaned and reassembled in by the next day. Thank you to everyone who helped. I'm putting the valve body in tomorrow, wish me luck.