Fixed My Clunkerado!

sternforpres · September 10, 2009

http://www.gm-trucks.com/forums/index.php?...mp;#entry903217

2000 GMC Sierra three door, 2wd, 5.3 automatic, 96,000 miles

My symptoms:

- Hard loud clunk going into reverse (only in the morning, when truck is cold)

- 50% of the time, slowing down to a stop I would get an audible clunk when the truck downshifted from second to first.

- Rare clunk upshifting from first to second.

- All other shifts seem ok

- Hard to describe, but at a stop, letting off brakes, I could feel a slight bind...almost like the axle was rolling up the leaf springs, then releasing.

If you have these symptoms, DO NOT CHANGE THE TRANSMISSION OIL, do not tow anything, do not "floor it" if you can avoid it, and if you are thinking of trading it...do it quick. I changed the tranny oil, and it blew up 24 hours later....stripped sun gear.

The good news is that a $1775 complete transmission rebuild (with new beast sun gear, upgraded planetary gear, and rebuilt torque converter) has fixed EVERYTHING. Actually, the truck rides so much better, I almost wished I had done this sooner, I have been living with all these horrible clunks, terrible ride, lousy shifts for so long...I feel like I have a new truck. Going to keep it until it dies now...

2005LT · September 10, 2009

Great to hear it's all fixed up now John. Sounds like it'll last for a while with the upgrades

splat10 · September 10, 2009

did it "miss" at high RPM in second gear? Mine almost sounds like a rev limiter if i getin the 3500-4000 rpm range (can only really do that in second). If i drive normally i have no other problems other than an occasional cluck upshifting into second.

See http://www.gm-trucks.com/forums/index.php?...=101679&hl=

Stevens03 · September 10, 2009

Glad to hear you got it all fixed up

sternforpres · September 10, 2009

I don't think so, the engine is still very smooth, except for the morning piston slap.

I can't remember the last time I was WOT. However, when the tranny detonated, I was taking a right on red, so had to get on it, I was going about 25-30 when I noticed that the RPMs were too high (it didn't shift into second, it stayed in first, but no rev limiter bounce), so I let off the gas and BOOM! The torque converter made a whining sound after that...so that was toast, along with the sun gear...not sure which one went first and if one caused the other.

I don't think you have a misfire, the sound you are hearing is probably a tranny/TC death rattle. The tranny should be shifting at around 4000, if its bouncing off 4000 and holding the second gear, its gotta be tranny related. Keep an ear out for new shifting noises.

If you know someone with a newly rebuilt GM tranny, go take a ride and you will probably be able to hear how bad off yours is. I wish you could feel the difference between my original tranny and my rebuilt one, its so sweet....my wife test drove it and came back with tears in her eyes...its her truck and her baby.

did it "miss" at high RPM in second gear? Mine almost sounds like a rev limiter if i getin the 3500-4000 rpm range (can only really do that in second). If i drive normally i have no other problems other than an occasional cluck upshifting into second.

See http://www.gm-trucks.com/forums/index.php?...=101679&hl=

ColoradoSkiCountry · September 10, 2009

Just as a FYI on the 99-2004ish GMT-800s, It was a very common problem for the Slip Yoke to "clunk" considerably when taking off from a stop or sometimes when shifting from 1st to 2nd or from 2nd to 1st. The problem was supposedly addressed by replacing the Slip Yoke with a Nickle Plated Yoke which they started putting in the trucks around 04. There was a TSB on this but it was not a recall item. My 99 Silverado had this from when I got her used at 60,000 miles, up to when I sold her at 120,000 Seemed to get worse over time.

Also, it is CRITICAL that you use the factory recommended Transmission fluid AS WELL AS the diff & transfer case fluid, or something equal to that. So many issues have been resolved as a result of simply changing to the reccomended fluid, including sloppy transmission shifting and diff & transfer case noise.

From what I understand, the fluid in the GMT-800s on up is a good quality synthetic blend with the proper additives in there. I do recall posts in the past of there being issues when someone ran a full synthetic tranny or diff fluid from Mobil-1, or Amsoil, or another brand.

splat10 · September 11, 2009

I don't think so, the engine is still very smooth, except for the morning piston slap.

I can't remember the last time I was WOT. However, when the tranny detonated, I was taking a right on red, so had to get on it, I was going about 25-30 when I noticed that the RPMs were too high (it didn't shift into second, it stayed in first, but no rev limiter bounce), so I let off the gas and BOOM! The torque converter made a whining sound after that...so that was toast, along with the sun gear...not sure which one went first and if one caused the other.

I don't think you have a misfire, the sound you are hearing is probably a tranny/TC death rattle. The tranny should be shifting at around 4000, if its bouncing off 4000 and holding the second gear, its gotta be tranny related. Keep an ear out for new shifting noises.

If you know someone with a newly rebuilt GM tranny, go take a ride and you will probably be able to hear how bad off yours is. I wish you could feel the difference between my original tranny and my rebuilt one, its so sweet....my wife test drove it and came back with tears in her eyes...its her truck and her baby.

Yeah i'm pretty sure it's the tranny slipping now or the tranny controller doing something wacky. I've not tried it in first gear but it's only second that i have it happen (but i've never gotten 3 or OD higher than 2500-3000 rpm.

I am due for a new filter and fliud change but the fluid is clear on the dipstick and at the proper level. I'm almost afraid to change it. I think i'll jsut drive it till it pops then junk the truck. The body is rotting off and all the bearings joints are starting to go.

sternforpres · September 11, 2009

Yea, good idea...just baby it as long as you can, maybe get AAA or some other auto club.

sternforpres · September 14, 2009

A quick update...finally got to drive the Sierra this weekend, man, what a difference. Some new things I noticed that were also fixed:

- I have the cloth bench type seat with the cup holders that fold down. At 30-40 MPH they used to shake so bad that if you put some pennies in there, they would jump out. I thought it was a suspension issue, but it wasn't...with the new tranny, no jumping pennies...the cupholders are almost perfectly still.

- Upshifts are so smooth, better than new...downshifts are go by unnoticed, too quiet to hear most times.

- In third gear and maybe fourth gear under 50 MPH, the engine is only turning about 1400, which seems lower than normal, at highway speeds, it seems to be running a little lower, but only by about 100 RPM or so.

- Much harder to stop quickly for traffic, when off the gas, the TC seems to be pulling pretty hard, so will not be tailgating now! Going to need brakes soon I bet.

- As reported before, the "axle rollup at stop" feeling is gone. When letting off the brakes at a light, and before hitting the gas, the truck rolls forward immediately...it used to feel like something was hung up.

- Highway ride is so quiet that my wife complains about the bug deflector making noise...uggg.

Will report any gas mileage change on next fillup.