1999 Suburban shifts late / high rpm
 

We were on the way home from camping today (not towing) when my Suburban seemed to start shifting late. It was fine on the way out and about halfway back. We went through a drive-through to get something to eat, when it started happening. I never shut it off the whole way home. And if I ease off on the gas, it'll shift.

A couple of notes:
While sitting in the drive-though line, I noticed a slight, occasional stumble while idling in line. Related?

Tranny fluid is relatively new. It was serviced not long ago. The shop dropped the pan went through it and said the tranny was in pristine condition. No shavings or anything, so they just refilled it.

Lots of variables,


can you tell me more about how many miles you have on drive train. any over size tires etc.


1.2 ton? or 3/4


Sounds to me like your
1. valve body pressure is off or stuck
2. TPS or shift kick down is off or miss adjusted.


I am not familiar with the assembly of the kick down.

3/4 ton. 143k miles. Everything is stock.

Drove it to work this morning to test more and everything shifted fine.

Maybe it was just a fluke. I drove it some more, did a test tow last night, and everything seems normal. Checked the fluid level and it was fine. Maybe slightly overfull.

I'll just keep an eye on it for now.

It's possible that the pressure switch manifold in the transmission is bad. It's an inexpensive part but requires the pan be dropped. It's bolted to the valve body.


The stumble is typical of these engines.

The fixed
 

What was the fix for this issue?

Ended up needing a transmission rebuild in the end. It mostly was fine for a little while after this post, but then stopped shifting into 4th altogether about a year later. We did a heavy duty rebuild since we tow a lot, and it's shifted perfectly since then. Local shop did it for about $2,300, which I thought was a great deal for a rebuild.

Side note: the occasional stumble during idle was completely unrelated. Replaced the spark plugs with ACDelco Rapidfire plugs, and the wires with MSD wires .Stumble cleared that right up and gave it much more power.

Still have the 'burb. We've done a ton of work on it since then.

https://cimg0.ibsrv.net/gimg/chevrol...bb1bd1ca7c.jpg