Weird Transmission Issue

Hey Guys. Wanted to see if you can help me diagnose the issue I am having.

I have a 2002 Tahoe LS V8 FFV 5.3 Liter.

I noticed the a month or so ago, after getting off the interstate, that the transmission was starting to hard shift as I began to accelerate after stops. Then as I paid closer attention to it, if I stayed on side roads and not go up above like 55mph, It never had an issue with shifting and ran like a top.

I got off the interstate over the weekend and it started to hard shift again. So, at the light I turned off engine and turned it back on and when I accelerated it, it shifted normally.

As I ran errands this weekend, I kept checking different driving routes and turning the engine off and on after interstate rides.

Its quite bizarre.

Anyone have any clue as to the problem? The check engine light is on but the code is reading hard shift only.

really hard to diagnose transmission issue's over the internet, I might suggest having a transmission shop check it out with there scanner, maybe have it serviced, could be as simple as actuators, when was it last serviced? how many miles on it?

I have had the truck for about 2 years now and I haven't hard it serviced yet. Not sure before the previous owner as to when they had it serviced as well.

247K miles

Joe Carter said:

I have had the truck for about 2 years now and I haven't hard it serviced yet. Not sure before the previous owner as to when they had it serviced as well.

247K miles

Click to expand...

I would run it by a reputable transmission shop and see what they say, with that many miles and unknown service history its a gamble on having it serviced or not.

I'd like to add that if you change the fluid and it starts slipping or something, the trans was shot anyway. Clutches were gone and the only thing allowing them to grab was the abrasiveness of the fluid, at which point its a waiting game to see if the gears, bearings, or oil pump lets go first from pumping grit.

3 outcomes in that regard
1. Trans is toast. Change fluid. Stranded now
2. Trans is toast. Leave fluid. Stranded later
3. Trans is "fine". Change fluid and either it's problem solved or no change


That being said you can get a good idea by just running the thing and examining the fluid. Are there any visible particulates? Odd smells? Is t notably dark in color beyond what would be expected for old fluid?

Edit: trans shop might be leery of touching a high mileage trans for that matter. Liability is a ***** and most shops are conservative

I have a bad feeling about this...

Its gonna be one of two things from what you said and what I have been reading. I change the fluid, it works or it get worse and basically dies out on me at some point.

And thats not the first time I have heard "liability issues" with high mileage vehicles.

If i took it to them, I assume most would say "its old and shot and I need to replace it anyways. 250K on an original trans seems like its last leg from what I have read.

Would I be able to tell by running it tonight and then getting home and check the trans fluid on the stick? I assume that would be the best way to check.

*non mechanic right here*

I think most shops are just going to recommend a rebuilt unit or to overhaul yours. The old fluid could be causing the issue with the valving or the actuators themselves are just getting finicky for some reason and benefit from a reset.