Chevy Transmission Problem ?

[Larry]

I'm running an '88 Chevy PU (C1500) Siverado w/ 69,000 actual miles. The last 35,000 have been towing miles w/ an 18' aluminum deep vee. 8,000 miles ago the transmission went out and I had it rebuilt and added a trans cooler. Just before Christmas, the darn thing went out again. I was driving in town and pulled away from a stop light only to be missing first gear...had 2'nd, 3'rd but no OD. Three weeks later it's back from the transmission shop (different one) and they say it was over-heated....replaced the pump, some clutch packs, and upgraded the power valve ?? I'm running a FI 350 with the 700R4 transmission which should handle anything I'm towing. I have no idea what's causing the problem. I discussed this with the tech at the shop and he asked about engine temps and gear selection. The engine runs cool and even cooler since adding the trans cooler. I run the trans in the drive range in town or pulling up a grade and then switch to OD for flat cruising.

Anybody got an idea what to check or what's causing the problem ?
This is getting expensive !!

[Mike E.]

Hey Larry, I have a 1993 GMC Sierra 1/2 ton 4 wheel drive with about 130,000 miles on it! My biggest concern was the transmission as well. What I do is change the oil and filter at least once a year. I pull a 24 1/2ft. fifth wheel trailer and my 16ft. crestliner behind that. Also what I did was put a very large cooler (12"x14" and about 1 1/2"thick) directly behind the grill so the air travells through this before it gets to the radiator. It takes an extra litre of oil now too! Be careful not to freeze it up in the winter months, I also put in a bypass so I can eliminate its use in the cold. A winter front might just as well help too. I bought this truck used about 4 years ago and have been pulling both units for at least the last 3 years. My mechanic can't believe its lifespan either.Hope I could help you in any way! Mike E.

[Captn Ric]

I had the same truck ,,put 285,000 miles on it on the original trany. We installed a drain in torque converter to get all oil out in changes.. We used the truck for roofing and towing trailers, it was the heavy 3/4 model with towing package. We just had good luck,, I have a 93 now with 165 K on it with no problems.. I have a new Ford also,, hope it holds out as well.

[Steve W.]

Sounds like somebody missed something on the first rebuild or possibly damaged something on the reassembly. Your transmission should always be ran in drive, not OD, when towing or carrying a heavy load. Keep an eye on the color of the trans. fluid, if it starts to get dark or yellowish have it changed. If you can keep it red/pink your tranny will live a long life. Best bet is to take it to your local lube shop and have it flushed, don't bother changing the filter, just get all of the old fluid changed out. This costs around $70 and is cheap insurance if you do it once a year. Steve W.

[Larry]

Thanks for the tips. I did check the fluid prior to taking it in to the second shop and it was just like new and had no burned smell to it. Also, second question on running it in OD. I asked the tech about not running it in the OD position when towing and this is what he told me.....said to keep it out of OD when the trans is doing lots of shifting (like in town) or if it starts downshifting when pulling up a grade. He said to use the OD position when towing at speed on level ground as the trans cooled more efficiently that way. He said all parts of the trans were working/cooling instead of the OD portion being locked out and not operating. I'm inclined to believe that the first shop didn't properly clean the trans the first time as it was littered w/ junk from some part that "vaporized" into lots of small stuff that looked like sand in the pan. I suspect that made short work of the rebuild job. The latest shop said they use a system w/ oil/solvent heated to 200 degrees to run through the system for 15 to 20 minutes to clean all lines and the cooler prior to re-installing the rebuilt trans.

It's been years since I fooled around w/ the old BW T-10 and the new automatics are way out of my expertise. I guess it's just a crap shoot when you go to have one repaired.