Hot Trans and No TCC/OD Problem

[Benesesso]

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 ~4+ years and 30,000 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!"

[LMP]

Interesting.
As you mention temperature range, there is very little chance this happens here in Quebec, the highest temperature here for at least 6 months in a year not going above your lowest...
Is this valve a part of the valve body in the side part of the transmission?....

[Benesesso]

Yes, it's located right behind the TCC solenoid. Supposed to be very hard to get to with the trans. in the van, especially since I'd think some drilling of the valve body would be involved in order to install the steel sleeve.

That clown GM "designer" has cost GM owners many millions of $$$$, and made trans. rebuilders rich.

[guido0136]

LMP - what are your thoughts? I live in Southern Ontario (Near Toronto) and I have that TCC problem. Adding an extra litre of tranny fluid helped a lot but this also sounds like a good idea. Do you think that it will be an issue with our winters?

Guido

[LMP]

I have not experienced that specific problem but would I have something similar to this description, I'd certainly use Benessero's advise ..I'll keep "just in case". It addresses a very specific problem.....so it is not a recipe for everything.

[guido0136]

Yup, I would hate for me to change the fluid and have it go bonkers.

I was speaking to my brother-in-law who is a auto mechanic, and he says to use syntetic tranny fluid, as it does not break down, as much, at higher temp.

Has any one tried this? If this is true I'm going out to purchase 5 litres of this...

[LMP]

If synthetic does in transmission what it does in the engine, I would consider this a real gift. Just record that since the coming of synthetic engine oil, guys in cold Quebec winter who drive their pick-up up the mountain and then just leave from there with the skidoo and return 3 days later no longer carry a coleman stove to preheat the oil pan when they return: they use synthetic: it is thinner in the cold, and thicker in the heat...the perfect fit.....and this is "the", if not the only, good reason to pay for synthetic......

[Benesesso]

Do those of you in cold areas have the no TCC/OD problem too? FWIW, I had tried Mobil synthetic trans fluid first but it didn't fix the problem. If anything the syn. was a bit thinner than non-syn.

I'd just use a bigger external trans. fluid cooler in cold areas.

[guido0136]

LMP - I was told to mix the synthetic with the regular tranny fluid, so you get the benefits of both.

Benesesso - When the temp drops below around +10C my TCC/4th problem is gone, and when the temp goes over +15C the problem starts, so if I lived in the Yukon the van would be sweet, but here in southern Ontario Canada, we can get winters as cold as -20C and summers as hot as +35C, so we need a fluid that can stay thicker in the heat but get thiner in the cold...... Where is Einstine when you need him....

[Benesesso]

Do you have a BIG external trans. cooler in front of the radiator/A/C condenser? I use a small one, because it was easy to slip in there. It helped a little, and eventually I'll get around to putting a big one or 2 smaller ones up there. But not today, because it's supposed to reach 119 deg F/48 deg C.

[guido0136]

I currently do not have an external tranny cooler, but will get one if the problem persists. Like I said, adding the extra Litre seemed to do quite a bit.

[southerncalm]

i also have a 94 Trans Sport and went through all the searches as well, the TCC Apply was a good one for me. also i checked and there was a recall on the vehicle. i never got contacted on it. so always look for recalls online before spending any of your own money

[LMP]

ALmost 5 year flashback....Glad for that thread recall....I did not remember, and was not kept in my "automobile favorite special"..

Since that thread last 2007 post, I had a condition ('93 3.8) for a short time: on one trip away from home in 2009 I had signs that transmission fluid intruded the main radiator ...so I bypassed the main radiator integral transmission cooler for the return trip. Most of the return leg then went only on 3rd and no TCC after 20 or 30 miles. BAck home I installed a small external cooler...and all got back to normal since.