Tranney slip

[Andrewhuffman]

In my 95 lesabre 3800, when the engine is cold, when in Od, only the 1st gear slips on the transmission. I can shift into D1 and it wont slip, and then back into Od. After a few miles or a few shifts, the car dirves as normal and dosen't slip. I changed the modulator thing that has a vacum line hooked to it, and it made no difference. Anyone know if i need a new transmission or can this be repaired, or if its another problem alltogether?

[wrightz28]

I thought '92 and up used the 4T60E? E-being electronic, no vacuum.

[Andrewhuffman]

i dont know, but theres a round thing on the front roght side when facing the engine from the front. it has a vacumline hookewd to it and comes off with one bolt.

[HotZ28]

Originally Posted by Andrewhuffman

i dont know, but theres a round thing on the front roght side when facing the engine from the front. it has a vacumline hookewd to it and comes off with one bolt.

That would be the modulator! The 4T60E used a modulator until around 1999 or 2000, I think. The 4T65E does not use a modulator! I assume your tranny works fine after the car warms-up? This sounds like the internal seals are leaking. You would need to do a pressure test on the tranny when cold.

[wrightz28]

Originally Posted by HotZ28

The 4T60E used a modulator until around 1999 or 2000, I think. The 4T65E does not use a modulator!

DOH!

my bad

[HotZ28]

Some good info on your problem here.

[Andrewhuffman]

How di i do a pressure test?

new info today. as i left for school and i shifted into D1, i was in a hurry and noticed a slight slip when i pressed the gas a little hard, not as bad when starting on Od. but i hope it lasts a little longer.

[mcqueary]

How do i do a pressure test?

You'll need to remove a threaded plug on the top of the transmission. Then screw in your pressure gauge in the hole where the plug was. Run the gauge into the driver compartment so you can watch the gauge from the driver's seat. Engage parking brake.

Start the engine, and keep your foot on brake at all times. First you run the tests at 1250 RPM with the vacuum modulator vacuum hose connected. The following readings assume your car is producing a vacuum of 18 inches. If not, apply 18 inches of vacuum to vacuum modulator using a vacuum pump. You should get: 74-95 PSI in P, R, N, D4, D3, and D2 and 158-170 PSI in D1.

Stop engine, disconnect the vacuum modulator vacuum hose from the modulator, plug the hose so you do not lose engine vacuum, start engine, go to 1250RPM, and keep foot on brake. You should get:
255-315 PSI in P, R, and N
165-205 PSI in D4, D3, D2, and D1

I would not leave the engine running with the vacuum modulator hose disconnected more than about 30 seconds - just long enough to quickly take the pressure readings as this puts a lot of stress on the transmission.

Stop engine, remove plug from vacuum hose, reconnect vacuum hose, remove gauge, and replace threaded plug on top of transmission.