[tobysws6]

Hope someone can give me some ideas. I just finished getting my 96 WS6 TA back together after changing water pump, radiator and transmission pan. It has been in my shop since October. I went to take it on a test drive to check it out. It shifts fine thru the gears until it gets to 4th gear. It feels like it stays in 3rd gear and the rpms keep rising as I go faster. When I take my foot off the gas it coasts and the rpms come down to almost idle. When I press the gas it just climbs back to where it was. If I shift it to third it catches and it pulls or slows down like it should. When I start the cat it does idle higher than it use to around 1300 cold and 1000 warm. I changed all my gaskets and cleaned the throttle body. I've read that it could be my tps or iac sensors. I didn't want to just change them if that's not the problem.

When I changed the pan I installed an aluminum pan to try and help my trans leak. I did remove the shifter cable to clean all the grime and oil around the trans. Could this have something to do with it?

Thanks for any help you'll can provide. It's time to get it on the road , having withdrawals from not driving it.

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[Mystery Bird]

Is the fluid level topped off to the correct level? If you're losing 4th then it sounds like the typical 3-4 clutch pack going bye bye.

 

[hrcslam]

I've never lost only 4th on a 3/4 clutch being worn. Although it is a possibility. If it is grabbing 3rd, I'd look into a solenoid first though. Then check the 4th gear accumulator.

Are you SURE you are in 3rd? What are your actual rpms at 60mph? 2nd will take you pretty high (My Suburban will do up to 78mph in 2nd gear on a LM7 at 5800rpm).

If it is in 2nd you have a 3/4 clutch problem and it's time for a rebuild. Ever do one before? I recently did my Suburban's 4L60e rebuild in my garage for $265 (upgraded clutches, steels, 8 pack 3/4 clutch pack, new seals, pistons, etc., plust the Transgo SK4L60e, and a hardened Sun Shell and fluids). If you have to tools and skill you can save a crap load of moeny rebuilding one of these your self.

Before you changed the pan, how many miles were on the trans since last rebuild? How many since last service?

 

[tobysws6]

Definitely still have third gear. Took it for another test ride to see. Shifts like normal until it gets to 4th. Then it just does nothing. I was hoping it was something simple like a tps or something. I'm not real firmiluar with transmissions. How hard is it to change the solenoid?

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[hrcslam]

Definitely still have third gear. Took it for another test ride to see. Shifts like normal until it gets to 4th. Then it just does nothing. I was hoping it was something simple like a tps or something. I'm not real firmiluar with transmissions. How hard is it to change the solenoid?

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Drop pan and filter. They are clipped to the valve body. But 4th uses a combination of solenoids.

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[hrcslam]

Ok. I did some research. The solenoids are good if you have first gear as both shift solenoids are used in first gear.

4th is engaged with the 3/4 clutch pack and the 2/4 band at the same time.

Since you have 3rd the 3/4 clutch pack is good.

The 2/4 band is applied by a dual hydraulic servo. So the band is activated by a pin that is pushed by one of two pistons located on the side of the transmission. It is possible for the 2nd gear piston to engage the pin but the 4th gear piston not to. This would cause your scenario. A broken/cracked or leaking 4th band piston can cause this. Also a worn band can cause this too.

What had been done to the transmission? Recent rebuild? Shift kit? How many miles since last flush/service?

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[tobysws6]

The car is a 96WS6 TA. I have had it since 97. It has 83000 miles and the only thing that has ever been done to the transmission was dropping the pan to change the fluid. I just changed the oil pan to a stock depth aluminum with a drian plug. I could not get the stock one to stop leaking. The only other thing I did was remove the shifter cable to clean everything up. I will be checking the oil level this weekend and then probably dropping the pan to see if I didnt knock something loose when I put it back on. I will also be checking all my vac lines along with my tps and iac sensors. Ive also read that if the if the tps sensor is bad it can cause simular problems with idle and shifting. Its time to get it out of my shop. its been parked for 6 months now.

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[hrcslam]

The car is a 96WS6 TA. I have had it since 97. It has 83000 miles and the only thing that has ever been done to the transmission was dropping the pan to change the fluid. I just changed the oil pan to a stock depth aluminum with a drian plug. I could not get the stock one to stop leaking. The only other thing I did was remove the shifter cable to clean everything up. I will be checking the oil level this weekend and then probably dropping the pan to see if I didnt knock something loose when I put it back on. I will also be checking all my vac lines along with my tps and iac sensors. Ive also read that if the if the tps sensor is bad it can cause simular problems with idle and shifting. Its time to get it out of my shop. its been parked for 6 months now.

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So you didn't change the fluid in 83k miles?

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[tobysws6]

Yes I did put new fluid. This was the third time I changed the fluid in the past year. I changed the filter a year ago and added new fluid. Pan started leaking so I dropped it again and resealed it with new fluid. Pan started leaking again. Bought an aluminum pan, installed it and filled with fluid again. When I drop the pan this weekend I will check the filter and probably change it to make sure I do not have a problem with it.

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[hrcslam]

Yes I did put new fluid. This was the third time I changed the fluid in the past year. I changed the filter a year ago and added new fluid. Pan started leaking so I dropped it again and resealed it with new fluid. Pan started leaking again. Bought an aluminum pan, installed it and filled with fluid again. When I drop the pan this weekend I will check the filter and probably change it to make sure I do not have a problem with it.

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Let us know. I'm interested top see what caused this.

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[Dynamic396]

You need to find out if the PCM is commanding a 3-4 shift.

Monitor the PCM data to determine if the 1-2 shift solenoid is being commanded on. If it is being commanded back on and there is no 3-4 upshift, then there is a problem in the transmission. If it is never being commanded back on, you have a problem elsewhere.

 

[exploring1978]

Bump… any resolution to this? I have a problem going into 4th, doesn’t happen till almost 60 mph and only then with my foot off the throttle, then even with the littlest throttle it downshifts (new tps)…

 

[exploring1978]

If anyone stumbles across this... the problem was due to Cruise signal. The ECM thought the car was in "cruise" mode, and was using the cruise shift tables. SOLUTION: change the cruise shift tables to match normal mode, or find the super top-secret place the ECM gets its "cruise" signal from. I have been unable to locate documentation on how the cruise signal is passed to the ECM.