95 Ts Se 3.8 (3800)

Let me try this again. While driving to Conn. yesterday going at 70/75 MPH I noticed my tach reading 3000 RPM's. I am use to seeing it at 2000 range while in lock up and cruising at 70. I did add 2 pints of fluid to the trans and it helped. Then on the way home it appeared to be doing the same thing but not going into lock up. When driving around town it works great, when doing 50/55 if I step on the brake the RPM's increase 250. But on the highway is where the problem starts. My thinking is maybe the modulator is acting up and causing the erratic shifting to 3/4/and lock up. Did a recent fluid/filter/gasket change and cleaned the pan of some sludge type material. Tranny ran good after and I feel no hard shifts or banging, but there seems to be a rumble at cruising speed. Info greatly appreciated. Van has 132k. Thanks for any help or replies. :runaround:

Failed Throttle Position Sensor will inhibit 4th, TCC and cruise control. Does your cruise control still work?

Failed Throttle Position Sensor will inhibit 4th, TCC and cruise control. Does your cruise control still work?

Ya the cruise still works like it should. My thinking is that the TCC is going south. Like I said round the city it's good, on the highway ................thats a different story:banghead:

My '93 does have a low fequency rumble that is most probably an ailing right half shaft cv joint. But that does not make it rev 3000 at 70......
There have been a few cases of failed tranny modulator on this forum. This is not an expensive investigation...check for vacuum connection to mod as it sees loss of vacuum like full throttle

Am I right, at 50-55 mhp, 4th gear and TCC is working? This means TCC should engage in 4th gear at 50 mph at flat crusing, with 1400 rpm. At 70-75 mph, TCC disables and the trans goes to 3th, with 3000 rpm?

My guessing is that you would find the code P0740, Torque Converter Clutch Problem. If above is right, I also guess that it is a TCC apply valve problem. The valve can´t hold pressure and the TCC disables. The difference between 55 and 70 mph is that the trans oil is slightly thinner at 70 rpm (trans oil slighty higher temperature).

I have no experience with this kind of problem myself, but I have read about it. There are several TS drivers in Germany (www.pontiac-transsport.de) with P0740 code and this kind of problems.

My guessing is that you would find the code P0740, Torque Converter Clutch Problem. If above is right, I also guess that it is a TCC apply valve problem. The valve can´t hold pressure and the TCC disables. The difference between 55 and 70 mph is that the trans oil is slightly thinner at 70 rpm (trans oil slighty higher temperature)..I have same symptoms as 99MBSport, and as Nicke guessed I have P0740 :mad: Any ideas how to repair this are welcome.... Thicker oil? I know there is a repair kit for the TCC apply valve, but you have to open gearbox. Repair manual says it is possible to remove valve body without having to drop tranny. has anyone done that?

I know that they make a rebuild kit for the valve plunger assy that goes into the Valve Body. You have to take out the valve body and ream the old area and apply a new sleeve and plunger. The problem is the older models wear out and fluid escapes by causing fluid blow by. I am going to do some research on this and see if there is an alternative to having to take the valve body out and redo it. Going to head to the JY and practice on a Junker to see what I can come up with. Maybe if I am lucky I'll find a valve body that has been sleeved.

Has anyone done that?

I know that there are some TS owner in Germany that have fixed the valve without dropped the complete tranny. I think they have just lower the left side of the engine/transmission. I will seach if I can find any useful postings at the german forum.

Thought I'd repost this and possible save someone much grief with the GM trans. factory screwup.

"Cheap Fix for TCC/4th Gear Problem

--------------------------------------------------------------------------------

My 1995 Transport developed "the common" problem of losing TCC/OD when the trans. fluid got hot. First I installed a small trans. cooler in front of the rad/AC cond. Tried piping it both ways-with and w/o the rad. cooler. It worked much better in series, with the fluid going thru the add-on last.

But the problem remained-it just took longer to lose the TCC/OD. Did a LOT of research into the problem. Seems some moron trans. engineer in GM managed to design the TCC apply valve such that the slightest leakage which got past the valve (steel valve sliding in the soft alum. valve body) would cause the TCC to disengage. The "stupid computer" would then sense the RPM mismatch-it had commanded the TCC to apply-so it then decides to prevent 4th gear (OD) from working. I live in Phoenix and the trans. temp. sensor never got hot enough to set a code-the problem was the trans. fluid getting thinner as it got hot.

I believe Trans-go or Sonnax makes a kit to replace this valve and add a steel bushing (what the trans. should have had originally), but it appears that the trans. has to be removed to install it. But there is another answer.

I decided to take a chance and use a thicker trans. fluid. I knew I was going to have to pull the trans. anyway if it didn't work, and then I'd have it rebuilt with the stronger heat-treated stuff etc. that also should have been used originally. I also wanted to regear it lower, because even with a good-running 3.8 the trans. was way overgeared-at least for me.

So, after making MANY phone calls, etc. I bought a 5 gal. pail of 50 wt. "Powershift" trans./hydraulic clutch fluid from a Caterpiller dealer. This fluid is used in earthmoving equip., and also comes in 30 and 10 weight. I dropped the pan and refilled the trans.-you can only get ~50-70% of the fluid out. Refilling with the 50 wt. gives about 30 wt. with the fluid that remains in the converter. What all this means is that I gained ~30-40 deg. F on the viscosity of the trans. fluid, and the problem disappeared. It has worked fine for ~5+ years and 40,000 miles so far.

The fluid is not expensive-I think I paid $35 for the 5 gal. They don't sell it in smaller amounts.

Several cautions besides the "do this at your own risk". Because I live in Phoenix, the lowest temp. is ~30 F. That means the trans. fluid is about like reg. ATF at 0 or -10 F--no big deal. But if I lived where it got colder I'd have used the 30 wt. for ~15-20 F "advantage".

The trans. works fine now, but I still put up with the gearing that I don't like. I'm just waiting for something else to break so I can remove it and rebuild it right!"

Benessero, I think you should duplicate your last entry in a new thread with a title that would make it easy to find with the search tool with using relevant keywords .

I know that there are some TS owner in Germany that have fixed the valve without dropped the complete tranny. I think they have just lower the left side of the engine/transmission. I will seach if I can find any useful postings at the german forum.

Sonnax have a rebuilt kit for the apply valve. Mattias from Germany has done the rebuilt. You can read about the rebuilt at his website: http://pontiac.ath.cx/index.php?option=com_content&task=view&id=50&Itemid=91 The website is in german, but there are plenty of photos!

Well I went out today and bought a 5 gallon pail of 50wt Tranny Fluid at the local Cat dealer, and am going to change the fluid tomorrow and see what difference it makes. I'll report back once it's done. If worse come to worse I'll get a rebuilt Valve bady and replace it. They are available for $299.

Well had to go back to the Dealer that sold me the "Tranny Fluid". It seems that there was a misunderstanding somewhere along the line and he instead gave me 50wt gear oil. I explained to them that I had asked for ATF not gear oil. After a run around he finally said he doesn't sell ATF. Well I turned around and lo and behold there was several 5 gallon pails of ATF sitting on the shelf right behind me. All were 30wtb but I decided to take my business somewhere else as these people definatly didn't know what the heck they had.:loser: I put 7 quarts of a fluid in called Purple something or other and it seems like it is running 100% better, but I am still going to try the heavier wt. fluid later on.

Seems like the problemis only when the fluid heats up and causes it to lose viscoscity. Maybe the "Purple Stuff" is more heat resistant.

Finally got the right fluid(Cat "PowerShift) and replaced it as in the previous post. Been two days and all is going good. I have been venturing further away each day and so for there is no adverse problems to report. If it breaks ,I'll rebuild, but for now the heavier ATF seems to be doing the job.

hello there,

I am new on this site. I found it when I start having problem with my 95 pontiac, and I found good answers.
now I have the same problem with the transmission, as is described here. I tried to find an ATF oil to a CAT dealer here, in Ontario, canada, but they are keep telling me that do not have something like this. I tried with "Powershift" option and they tried to sell me "Drivetrain oil, used for transmission, wet brakes, etc. Is this the same oil as you use it in your transmission ? I am wiling to give a try before starting something else.
thanks

Sonnax have a rebuilt kit for the apply valve. Mattias from Germany has done the rebuilt. You can read about the rebuilt at his website: http://pontiac.ath.cx/index.php?option=com_content&task=view&id=50&Itemid=91 The website is in german, but there are plenty of photos!
Babelfish (http://babelfish.yahoo.com/) helps with translation.

>" I tried with "Powershift" option and they tried to sell me "Drivetrain oil, used for transmission, wet brakes, etc. Is this the same oil as you use it in your transmission ?"<

Yes, it is the same. Try their new "TMS" multi-grade oil, especially because you live in a cold area.

thank Benesesso, I shall go today and buy some oil from them.Thanks again and all have a great weekend

ok, now I have the oil in 30W.I spoke with one of the guys there, and he told me that they are not using the multigrade from 3 years now, because they discovered that the gears broked the oil in heavy duty applications, so since then they are using only the 30wt for this area and he told me that they have no issues so far.And they didn't have any other grade there.
this is just as an information.I might be wrong, so don't take it as a sure fact.

Interesting. Cat's own data shows lower gear wear for the multigrade vs their single grades. They used 30 wt. in the winter and 50 in the summer.

The trans. gears in our vans apparently are only lightly loaded, vs. an earthmover that is always straining against the dirt.

The only difference I found with this OIL/FLUID is the color. The original Tranny fluid is Red in color and the Gear oil from CAT is clear. I put the 50wt in the van and am still going strong after 3900 miles. Shifts good has good pulling power, and runs quieter. I was really hesitant to use this but I said "hey what do I have to Lose?"

well, I changed the oil with the 30wt from CAT. My transmission is still a little bit confused in changing from 4th to 3rd. Its seems that using the 30 wt in combination with what's left in transmission (I did not purged the transmission, I just took off the pan ).
I'll try to do the same thing someday this week, and may I'll add some Lucas additives in to see what happens.If I'll still have the problem....well the worst case scenario...anyway, have a great week