Question about 2004 Chevrolet Avalanche
I was driving and there was a loud clunking sound. I lost power in D gear. When I shifted to 1, then to 2, then to 3, it would drive. It slipped in 3, though. Reverse and park work well. Anything I can do or check myself before I take it to the shop? It has 208K miles.
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Posted on Jan 02, 2017
Are you getting the check engine light? If so the electronics may have gone out. You may not need a rebuild but you won't know till you pull the oil pan on the transmission and inspect the contents. You may also have lost the neutral safety switch. It is mounted on the drivers side of the transmission. Check those out first and let me know what codes you get.
For Ponchoboy; the clunking and hissing you hear are teminal root causes. Drop the oil pan and if it has a lot of filings and metal it is time for a rebuild.
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Posted on Feb 09, 2009
Well your clunking noise is most likely the u-joints the leaking pan is the tranny pan what you would have to do is get a tranny kit and change the pan gasket tranny filter and fluid or take to a shop and have a tranny service done.
Posted on Sep 02, 2009
Testimonial: "thanks a lot, man. i will def do what you suggested. Im gonna try and fix it on my own. hopefully i dont mess it up and it works. ha ha. thanks again!"
Before guessing at transmission problems, check the fluid level (car warmed up, engine running in Park on level ground) and have the PCM scanned for trouble codes FIRST.
Secondly, put a line pressure gauge (or visit a local trans shop) on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.500" boost valve (easy fix in pan).
Slow, slipping or no reverse: “lo-reverse” clutches are worn out, fluid leak in the reverse apply circuit, or broken sunshell. It is possible to remedy a fluid problem by removing the checkball from its cage in the case in the rear of the trans may help (must remove valvebody), or adding a high-viscosity additive such as Lucas Transmission additive or other seal restorer product. May also have worn boost valve (can replace in the pan).
Soft shifting, gradual performance degradation: Poor line pressure rise due to leaking boost valve, clogged EPC filter screen, failing EPC solenoid, or worst case: leaky seals throughout. Transgo HD2-C kit fixes first two without removing trans. Seal restorer may fix last problem, but probably R&R. Also try a transmission flush with BG brand products (Firestone stocks it).
No movement in any gear: pump failure, or total loss of fluid. R&R, or refill pan and find the leak. If out of fluid, avoid running the engine until the trans is refilled to avoid pump damage. To check for pump failure, check fluid level with the engine off, then start the engine and recheck fluid level. If level does not go down when engine is running, the pump is broken.
1-2 or 2-3 shift is slow/soft above part throttle: Trans is on its way out. R&R
Good luck and start with checking your transmission fluid level. Thank you for using Fixya
Posted on Mar 16, 2010
It doesn't sound like a solenoid, check the universals and if it's not those, it is more than likely a linkage problem,
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Posted on Apr 06, 2010
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