New question...not about me this time. Thirty year old son called tonight down-in-the-mouth. Said he checked his auto trans, found it, "low," so added right up to top. Then he said it suddenly would only produce reverse, 1st and 2nd gear. No third or OD. I asked if his old fluid was kept fresh and smelled clean and he said, "yes." He's 300 miles away, so hard to run over and take a look. Truck is '97 Silverado 350 1/2-ton, 4WD with 180K on clock. He is not sure of trans model, but thinks it is a TH350. He knows a fellow at tranny shop so expects to limp it in for a diagnosis. I doubt the transmission has ever been repaired/replaced, etc. This is his work truck so he depends on it for his living; it was never a heavy hauler or packed trailers, etc.

I just thought I'd post the rough syptoms in case anyone knows these units fail in any certain manner or mileage.

General comments appreciated. New Year's Day isn't always great for everyone. Thanks, Dennis

my '98 z-71 did the same thing at 99,000 miles. it was the planitary out shell or something like that, it was major and required major overhaul of the transmision. about $1500.00.

Thanks, Mike. That's not good news for the boy because I can easily believe he could have major trouble too...especially at his 180K on the clock. I have a heavier (I think) trans in my '92 1-ton, 6.5L diesel and there is 169,000 miles on mine. Not sure if the PO ever did anything major to mine either. So far it's perfect except for a pan leak.

I'd really prefer stick-shifts on these $%@#&*% trucks just for the reason that the automatics are so unpredictable. I think there are legions of AutoTrans tragedy stories in the world of full-sized pickups. And costly.

Dang.

Dennis

Is it the TH400 or 4L80??

Ken, you asked which trans...not sure if you are referring to our boy's '97 or my '92. He's not sure but thinks it is a TH350 trans.

When I bought my '92 1-ton diesel, I went to my cousin who is the parts guy in a local Chev dealership. He pulled up my VIN and printed the option codes my truck came with when new. They I borrowed his code-conversion book and stood at his counter through his lunch period writing down what I had in real words. So....."I" have:

code MT1 = 4L80E HD Trans

code MX0 = Auto Overdrive

code G80 = Posi-Limited Slip

I do not know the difference between my trans and the trans model TH400 you mentioned. We always knew the, "TH," to be "turbo-hydro," but what happened between the TH400 and my 4L80E, I don't know.

BTW, I'd LIKE to know the differences or common life expectancies. Although I also believe how long these darned autotrans last is a complete gamble.

This help?

Oh, I mentioned the code for Posi/Limited Slip because that code evidently can mean I have "either." I guess I can figure out which by wheel rotations.

Dennis

Here is a hint, the TH350 tranny is an older model tranny (W/O overdrive). If the tranny is in a 97 truck, it should be one of the two, a 4L60E or a 4L80E tranny. These are computer controlled trannies, with the 4L60E being the equivalent of a 700R4 tranny (lighter duty) and the 4L80E being the heavier duty tranny.

I guess one should define as to where did your son fill the tranny to (reference the top that you discussed). Is that the top of the dipstick, or the top of the tube? Did he fill it while the motor was running? You check and fill an auto tranny while the motor is idling and the tranny is in "PARK". If he filled it while the motor was off, then the chances are the tranny is not filled right.

As for the symptoms, the loss of third and OD, could be something as simple as the governor failing, or a stuck servo vavle inside the valve body, then again the unit in the back could have failed.

I have a 700R4 in my 91 and it failed at 150,000 miles, but that gave me the reason to build it up for performance, I now have 210,000 miles and going strong.

Maual trannies fail, also---synchros, gears, clutches, throw out bearings, and the like.

Thank you for clarifying trans models. We haven't heard back yet on what he found out. Boy's filling trans, "..up to top," as I wrote, is my poor sentence structure. And he should be smart enough to fill correctly or darned close to it. Doesn't mean he didn't overfill it some.

Some of my preference to stick shifts come from a feeling that when they begin having trouble they let you know way ahead of instant failures.

Doesn't sound there is any particular clock mileage when these things typically fail.

Dennis

Boy called. Shop said trans is toast; something about 3 gear clusters gone. Quoted him $2,400 for, "new," trans installed in his 4WD.

Boy is probably home drinking as I write this.

Thanks for the help everyone.

Dennis

$2400.00 is about right for replacement, in this day and age, especially with the 4WD.

Hi Dennis. I would suggest checking at the local Chevy dealer for a factory rebuilt trans. They come with the lastest updates and it has a warranty. My uncle and my best friend both went through the same thing and both went the GM rebuilt route.

Good point on GM. The boy already called back. He found, "A-1 Transmission," near where he lives in Blaine, NW Washington state, and they already have his truck in their shop. They quoted him $1,700, to R&R (rebuild) his and provide 2-yr. warranty. I'm afraid I am usually skeptical of transmission rebuild shops, but he says he has several friends who have very good luck with them. So, ....... we'll see.

All this makes me more nervous about my '92 with 171,000 miles on it. I've only had it about 10 months, I serviced the trans thoroughly right after I got it and the fluid smelled and looked very good even at purchase time. Unfortunately, I don't know if the PO ever rebuilt/replaced it or if it is getting close to failure now. It works perfectly at present, I just need to replace it's pan gasket (dripping). I wish they would not fail so suddenly. One thing if failure occurs close to home, quite another in a distant small town where you've never been before ! I don't see an answer to this.

I'd be curious what the GM factory rebuild and R&R cost?

Thanks,
Dennis