95 Transport 3.8 Overdrive TCC Sensor problem(s)

[Ufgator]

I have 1995 Pontiac Transport 3.8/4T60E with 165K miles (bought it with 65K)

Currently, the RPMs are different on different occasions at around 55 mph. They can be 1500, 3000 or anywhere in between 2100 and 2600. I also have a shudder that occurs on occasions when I’m at 1500 RPM. I have recently replaced the plugs, wires, fuel filter and had the transmission serviced.

I am assuming that when I am at 3000 RPM that overdrive (4th gear?) is not engaged and neither is the TCC. Does the TCC lockup when you are in 3rd gear? I am assuming that the TCC and 4th gear are different even if the TCC only locks up in 4th (or is this incorrect?)

At 1500 RPM I figure I’m in overdrive with TCC locked up. When I get a little shudder I press the brake a little and I go to just around 2000 RPM and the shudder goes away (this is overdrive and no TCC I am assuming)

But what is going on when I’m at 2100 to 2600 RPM? No shudder that I can remember. Am I in overdrive? Is the TCC engaged but slipping?

I recently tried to disconnect the TCC but this did not work since the van kept stalling and I had to reconnect it within two blocks. That seemed strange since I kept reading everywhere that this could be done. I also disconnected the EGR an did not get any shudder but never got to 1500 RPM either.

I think temperature has a major effect since this morning was a nice 50° F and everything was great for the first 20 minutes ... then I started to get the shudders (after everything got hot?). I was at 1500 RPM. This afternoon was around 65° F and I never got to 1500 RPM it stayed around 2200 (but this was right after cleaning the MAF).

After seeing the 95 Transport post I cleaned the MAF and got a TCC error code (not the one from disconnecting the TCC since I had cleared that one). Can a dirty/bad MAF cause shudder or prevent overdrive from engaging? Lets see what the 30 min drive home has to offer.

I am about to have the solenoid, and a related relay for it, replaced. I read the TCCSHUDDER.jpg from LMP's list but that did not seem to eliminate the solenoid although it seems to have eliminated the transaxle (my shudder occurs after the TCC has been engaged for a while).

Thanks for your time and sorry for taking so much of it. Any ideas would be appreciated.

[LMP]

Originally Posted by Ufgator

at 3000 RPM overdrive (4th gear?) is not engaged and neither is the TCC. Does the TCC lockup when you are in 3rd gear?

3000 in 3rd at 55 no lockup seems a little fast but OK in robust acceleration and going uphill ....and Yes lock-up will engage in 3rd in D range but on OD range, shift to 4 may occur before engaging TCC

Originally Posted by Ufgator

At 1500 RPM I figure I’m in overdrive with TCC locked up. When I get a little shudder I press the brake a little and I go to just around 2000 RPM and the shudder goes away (this is overdrive and no TCC I am assuming).

Affirmative on all

Originally Posted by Ufgator

what is going on when I’m at 2100 to 2600 RPM?

all possibilities you mention are plausible

Originally Posted by Ufgator

Disconnect the TCC did not work since the van kept stalling

I can't explain that one....except the same plug also controls 2 solenoids that override hydraulic commands. But the transmission should have operated quite normally except shifting would not necessarily occur exactly at same rpm. Combined with your other symptoms I'd think some pressure is inadequate somewhere....damaged seals or the like is a possibility

code 21 or 22 (TPS) (these are OBD1 codes..may yours is OBD2) will disable 4th, TCC and cruise control . In fact an intermitent TPS problem would explain all of the above, except TCC shudder that points either to worn out TCC clutch or internal pressure leak.
Question: WHen you succeed in obtaining 4th and TCC, will it accept a mild acceleration without slipping? (just a little more throttle applied gently so TCC is not switched out

[Ufgator]

Originally Posted by LMP

Question: WHen you succeed in obtaining 4th and TCC, will it accept a mild acceleration without slipping? (just a little more throttle applied gently so TCC is not switched out

I went out for a drive and waited until I got to 55 and 1500. Pressed the accelerator a bit and I got shudders more than half the time (around 10 tries). I also tried it when I was at 40 and 1500 and got a jump in RPMs of about 400-500. Is shudder equivalent to slipping? I figure the jump is normal because the TCC is not engaged and/or I am still in third (is that right?).

As for your comment concerning the loss of pressure somewhere ... I had been thinking about that ... sounds like something really hard to pinpoint.

[LMP]

Shudder is like a vibration, like clutch engaging and disengaging in rapid succession. If TCC is ENGAGED and the TCClutch slips, when you try a mild acceleration, because of worn out TCC clutch or insufficient pressure, it will possibly "shudder" or you might also have a shooth "slip" with engine RPM going slightly up and coming IMMEDIATELY back to TCC lock RPM if you release throttle slowly. However, if you change the throttle position faster (either in or out) then the TCC will release and then, on acceleration, you will have higher RPM due to TORQUE CONVERTER hydraulic slip. Torque converter slip is normal (fluid coupling) , while torque converter CLUTCH slip (mechanical) is not normal.
NOtice that a lack of pressure in the system might also make other clutches slip.......but since torque converter clutch is much smaller and designed to handle only steady speed torque, any lack of pressure would cause the TCC clutch to slip first.

[wolbrink1]

I have a similar problem with a 1993 silhoutte with a 4t60e and a 3.8L 150000 miles. My problem seems worse when warm. My only problem is when I am about 50-55mph with light throttle prossure rpms will go to about 1500 and shudder. Replaced fuel filter, plugs and wires. Would like to just disconnect the overdrive but evidently that wont work. Any suggestions would be appreciated.

[Ufgator]

I ended up having the TPS sensor replaced and this solved 98% of my issues. On occasions I still have a slight shutter. I have recently replaced the vehicle with a 95 Transport Montana so I gave up on solving the shutter problem.