Trailblazer Transmission Noise

re: chevy trailblazer 2007

Between 1,000 and 2,000 rpm (only 20% of the time) I hear, and feel, a clunk that seems to emanate somewhere near / behind the driver seat. The error code (an 834 ? possibly but I forget exactly…but def in the 800 series) says " transmission component slipping".

Trans oil full, and clear.

The clunk sound happens on any terrain, and is very random. And going up-hill does not bring it on. The clunk’s been happening for about 2,000 miles.

The orig transmission was replaced 15,000 miles ago.With a used one. Total mileage on car now 75,000.

Mechanics give varied explanations, and prognoses (none are good) but no one knows what’s going on for sure.

What’s your thoughts?

P0894 would be Trans component slipping

P0834 would be Clutch peddle switch B circuit low

The P0834 would be an easy fix, but if it is the P0894 I’m afraid that it is going to be expensive.
That would indicate that the converter is slipping.

Find an independent tranny shop to diagnose the problem. Do not go to a chain shop. They are only interested in replacing a tranny and many times do not have the training invested in their mechanic’s that an independent shop would.


“Find an independent tranny shop to diagnose the problem. Do not go to a chain shop.”

+1 for @Yosemite .
I’m afraid that is going to be the best advice you will be able to find. I was going to suggest the exact same thing.

4wd? The transfer case is under driver seat area. Very easy to not plug in 2-3 wire harness connectors on trans swap. You did verify transfer case fluid level? Or perhaps you have a 2wd? Very rare in my area.

I’ve owned two TBs; an 04 and an 05. I spent quite a bit of time on the Trailvoy site that is particular to these trucks. One common theme; frequent fluid swaps are very beneficial to longevity for these trannies. I don’t let mine go more than 30k between fluid changes.

You have a used trans now that clunks only rarely. These trannies are expensive in both unit and labor costs to replace. Unless you are super risk averse, I would drive it until it gave up the ghost unless you can find someone to diagnose it as something inexpensive to repair.

If you can post the actual diagnostic code, perhaps a more definitive assessment can be made.

Code is PO894, certain. The guy who replaced the first one said there’s a chance it’s the circuit between the motor and tranny. Cost to replace $180.Have to turn a knob to get 4WD.

Another tranny guy said car will last 1 day to 1 year - know one knows.

Yeah, that’s not good. Bad circuits usually show up as sensor input errors. Seeing the slip error code means it is reading input and output speeds and they don’t correlate to the selected gear. Have you noticed the rpms being slightly higher than normal? Have you been able to tell what gear change is affected (1-2, 2-3…)? Or is it just cruising along in a particular gear and doing the deed?

So yur saying it COULD be the circuit? No I haven’t noticed gear or rpm specifics.