Chevy & GMC Vans

This weekend while towing a utility trailer with 2 small quads on it through the mountains of Vermont, my 'service engine soon' light came on and the trans started shifting very hard.

At 1st it was just the 1-2 shift, then later on it was the 2-3 also. Both shifts were also very delayed no matter how hard or soft I was on the gas pedal.

I checked the fluid and it was good.

On the return trip it acted up again after it was fully warm, like 75-100 miles of driving. This time we stayed out of the mountains and stuck to the 'big' road.

On the return trip we stopped 2 times, (food and gas) each time the problem stopped for a while and then eventually acted up again after getting hot again.

The light has not been off since it originally went on, but the trans is shifting normal the last 2 days going to work and back, about 10 miles each way.

I do remember reading something here in the past about a shift solinoid causing a harsh shift, could this be my problem? Can I replace this myself w/o getting inside the tranny?

How do I pull a code and shut the light? I remember something years ago with my last astro, using a paper clip and testlight maybe??

I dont have a tranny cooler installed, but do have one that I will now install before the weather gets real hot.

This is a 2000 astro with the 4 speed overdrive trans, with the tow/haul button.

I did leave it in the tow haul mode for 80% of the trip. What does that do for the trans, it seems to shift a little later with in engaged, not sure if the OD engages or not when it is in tow/haul, if it is doing it its going in very late and soft. I wish I had a tachometer.

There is a little over 100k on this van, not sure if the trans fluid has ever been changed and not sure if I should change it now or not. Ive always heard that if its never been done by 100k, leave it alone.

Thanks

You'll need to read the code and erase the "Check Engine" light with a scanner. Then the cause of the malfunction can be addressed. By the way, that's an excellent post.

What color is the fluid? If it is real dark, almost brown it is too late to do much. If it is still red and doesn't smell burnt you can drop the pan and change the filter. When you do this, install the aux cooler and flush the whole trans with synthetic fluid. You can use one of the cooler lines to do the flush.

The code will need to be read with an OBD-2 code reader. My guess will be it shows you have a P-1870 which is a slip code. I had this years ago and fixed it with installing a 700R4 inner pump spring in place of the TCC servo apply spring. The new spring is longer and stiffer and it applies the TCC instantly. I also switched to Amsoil synthetic fluid and even when I had tranny temps of 250 degrees (towing in bumper to bumper traffic), it shifted perfectly. There are other fixes for the 1870 code as well.

With tow/haul, the trans will still lock the TCC in 3rd. I have found running for extended speeds (interstate) in 3rd that the trans temp will still climb pretty high even with a monster cooler. A temperature gauge will become your best friend in determining how hard you can push your van and also when to let off and let OD cool things down.

Let us know the fluid color and smell as well as the code. Autozone, and other parts store should be able to read the code for you.

all things tranny at great prices, this is where I bought my LPD cooler among other things.

http://www.bulkpart.com

Fluid was still pink/red and smelt normal the other day, was full too.

I tow a camper with my fullsize dodge van, I have a trans cooler in there with a trans temp gauge. That tranny runs cooler in 3rd when towing, I dont use OD at all with the camper, even on level ground because the trans gets hotter.

With such a light load on the astro, probably only 1000lbs or so, I wasnt ever thinking about a temp gauge and had even forgotten about the cooler I had in the garage. I guess I will install the cooler and shop for a gauge.

So I cant pull the code like I did with the old 88 astro, I think I counted flashes with a test light, a certain number of light flashes equaled a certain code.

I never felt a slip from the trans at all, just very hard shifts.

My nephew has a code reader, I will get in touch with him, or hit an autozone.

There isnt some sort of solinoid to fix this hard shift, I thought I had heard of this someplace before. What is the TCC?

Thanks for the info so far.

The TCC is the torque converter clutch. There have been a couple different fixes on here. Just look through the old threads.

Get the fluid and filter changed and get that cooler installed. Clear the code and I bet it won't come back on towing that light load.

Surprisingly the light was out today. Shifting has been fine since Monday.

I stopped at Advanced auto parts, he hooked up a scanner but he said if the light was out it wouldnt pick up a code. He was correct, no codes stored. He said the dealership scanners would pick up a stored code. So tomorrow Im gonna try Autozone and if still no code, then I will try my nephew at the dealer.

wouldn't Dans van already have a factory cooler installed?

Just the one in the radiator and that will get the tranny to 180 - 195 in normal driving.

I looked at it today, just the factory cooler that runs into the radiator, that and an engine oil cooler that also goes into the rad.
Doesnt look like a lot of room to get in there to add a cooler.
I have to make some time in the next few weeks to do the cooler and a fluid change.

Once you have the grille off you will see there is lots of room for a cooler in front of the radiator.

It happened again today. While towing the quads, after about an hour of driving, the tranny started shifting hard then the light came back on.

I wasnt in the mountains, just small hills, and wasnt pushing it hard at all. Once it started acting up, I put it in tow/haul mode.

Coming home I used tow/haul the entire time and the shifting never acted up, but the light stayed on.

I hardly feel the load of the trailer and the quads so it cant be that its to heavy of a load for this van and heating up this tranny to bad. The temp was only 63 here today.

Im gonna try to stop at the autoparts store on my way to work to see if they can pull the code for me.

Let us know the code.

Then throw the tranny cooler on and the problem will be gone. It IS a heat issue as any more than empty driving will send the trans temps over 200 pretty easily.

Got it tested last night, p1870

Today the light is back out.

The printout says, possible trans slipping detected, low fluid, towing heavy load, or failed transmission.

Gotta find the time to get the cooler installed, not gonna be easy, working to many hours and will be away this weekend. Maybe next weekend.

LiftedAWD, that spring that u mention, for the p1870, that would require pulling the tranny out??