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Old 09-10-2009, 06:40 AM
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4l60e slipping in reverse

This is my first post,

I have a 94 buick roadmaster wagon with 80k miles and stock 2.56 gears.
The trans is currently out of the car because the I ordered a performance trans. However that perf trans did not last 20 miles and I returned it to the vender( very long story)

I am now debating whether or not to try to rebuild my trans myself. Heres my problem.

The trans has started to slip most noticably in reverse. Under moderate acceleration in reverse there is a shudder along with slipping. This condition is worse when hot. Also put a bottle of lucas in and it helped. The trans fluid does not smell or look burnt. I removed the pan and there is very little clutch material in the bottom and no metal particles. I also pulled the pressure controll selenoid and inspected the screens. It is clean. I checked the resistence of all selenoids and they meet spec. There is also a whine at idle when the car is in gear. I did not check line pressure because I did not have a gauge when the trans was installed. Trans shifts fine and torque conveter locks up normally. Any ideas of what this could be? Is this something I can fix without going too deep inside the trans?

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Old 09-15-2009, 06:10 AM
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Here is an update. I checked line pressure in in park and drive line pressure is between 55 and 200 psi. 55 at iddle and 200 psi at WOT. Trans shifts and feels fine in all forward gears.

Line pressure in reverse was 65 to 70 psi at idle. When I started to accelerate( lightly) in reverse line pressue went up to 120psi. However it began to shutter and I backed off. So i do not know what max revese line pressure is.

I found a post from 2007 which mentions there is a bleed hole in the reverse input drum piston which could allow too much fluid to pass thus reducing line pressure.

There is also mention of "opening up the separator plate to increase oil flow when reverse is applied".

Do you think this will fix my problem and has anyone tried this?
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Old 09-15-2009, 06:25 AM
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So, did you replace parts in the original trans and reinstall it? Or simply bolt it back into the car?

Is this the original trans mileage and age? 80k miles and near 16 yrs old?

You have a weak clutch pack form the sounds of it. If the main line pressure increased at light throttle to 120 in reverse , that is enough pressure for the trans to operate.

The shutter is from the clutch pack not holding power
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Old 09-15-2009, 06:57 AM
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here are answers to your questions

"So, did you replace parts in the original trans and reinstall it? Or simply bolt it back into the car?" I did not replace any parts just bolted it back in the car.

Is this the original trans mileage and age? 80k miles and near 16 yrs old?
Yes original trans with 80k miles and 16 yrs old. According to service records it has never been touched except for fluid changes.

I was planning on modding the car. My long term goal is lots of low end torque, max rpm around 5500 and 2000 stall converter. I want to keep it very drivable and street friendly. I would like the trans to be able to hold up to 450lbs torque. The car will most likly never see the track. I have a set of 3.73 gears and a limited slip diff I am going to be installing shortly but i wanted to get the transmission addressed first.

At this point do you recommend a complete rebuild or just address the reverse clutches?
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