First of all, would like to say that I have found lots of good info on this site. VERY nice work folks. Anyways, I have a 1996 4x4x4 4.3L auto W/OD Blazer. It had a new engine @115K Now has 150K on odometer. Blazer drives great, shifts fine, 4x4 works Etc. Heres the problem. When highway driving and going downhill I remove my foot from the gas, to coast, let the car hold speed, and the motors rpms shoot up like you are reving the car in park or nuetral. (I don't have a tach) but you can hear it. Also the speedometer fluctuates about 5 mph. This doesn't happen if I keep pressure on the gas or tap it constantly. Also applying the brake gently keeps it from happening. BUT if you apply the brake hard ie traffic backup it will happen. When this does happen I can fix it by pressing the gas, which seems to cause it to "catch" or by shifting to nuetral then back to drive. I can also put the car in nuetral going downhill and it won't happen. It feels like something is not applying pressure or "free" spinning".

Thanks for any help
Shaun in tahoe


P.S This occurs in any outside temp. 0-85 degrees, With or W/o heat ,Ac on/off .
Oil pressure stays the same, Have no change in the voltage reading either

 

Normal.
Your torque converter is unlocking. It locks back up when you give it gas. It should also unlock when you touch the brake. The engine will flucuate about 200-300 rpms witht he torque converter lockup/unlock.

 

Thanks for response. Still, it's Pretty loud and seems like I'm rolling in nuetral. No back pressure, down shifting? @ all. Never seen this in any vehical before.

 

THERE IS NO WAY THIS IS NORMAL!!!!! Sorry Hanr3 but this isn't normal. Eveerything I can find points to a bad torque converter or sensor. Possibly The TCC ? Anyways its not unlocking, it is fully disengaging thus "free spinning". It only happens going downhill,the car can't hold its own. ANYONE ELSE HAVE ADVICE?? All help is appreciated. Thanks

 

I want to be sure I am reading this correctly... When you are coasting down a hill, the RPMs rise, seemingly uncontrolled?

If that is the case, I guess I would have to ask what the RPMs rise to for a given speed? What is the engine RPM when you put it in neutral under the same circumstances? What about engine RPM after you tap the brakes given the same speed and slope? Specifics here will help us better understand the problem you are trying to describe.

 

I had a nice long response, however the site didn't save it. Besides it appears you dont want my advice anymore.

couple of questions.
How long have you been driving this road in this truck?
What color is your tranny fluid?
Is your tranny fluid full?

Try downshifting into 3rd gear instead of coasting. What happens.

If your torque converter was going out you wouldn't be able to accellerate and the tranny wouldn't shift fine in all gears or while in 4x4. Your torque converter is like a clutch on a manual tranny. The torque converter provides a mechanical fluid linkage between the engine and tranny. Coasting at highway speeds is when teh torque converter is under the leaast amount of force.

Guess again!

 

Hey guys first just want to thank you for the input so far. This is just getting frustrating. Yes the fluid is fine, doesn't smell burnt, is a good red colorand the rmps seem normal when in nuetral etc. It is more of a feeling that the is a lack of pressure/force. the engine doesn't seem able to hold itself back. something is definately "free spinning". If I down shift it to try and slow down, It has "spun" on me a couple of times also. This engine only has 35 K on it, but if not the trnas, torque converter, could it possibly be the timing chain/belt spinning? If so shouldn't it have blown the engine?

thanks Shaun

 

What is your idle RPM in park and in gear?

 

I don't have a tachometer, but the car seems to be idling somoothly in park and in gear. (compared to other cars) Also, maybe I'm just not explaining it right? When this happens, you hear a very loud Whinning sound, its as you were sitting in your driveway, in nuetral, and flooring the pedal, but without any compression feeling more of a free spinning feel. Hope this is helpful Also the car seems tobe startingtopicking up motion/speed do to the gravity of downhill right before it spins out. I believe the speedometer is connected to the transfer case? And I see a slight variation in the speedometer when this happens could it be the transfer case or part of??? Once again THANKS FOR ALL THE HELP

Shaun in Tahoe

 

MAY GM BURN IN HELL
I guess know one has any more info, or doesn't want to admit how much GM sucks! After more research, and talking to someone at the dealer, who doesn't think GM is reliable either, I discovered the problem. All I will say is Know wonder GM is failing. For all of you who are sniveling GM freaks, Quit CRYING!! I will never by GM again!!! By the way this site is pretty weak
Good bye forever
MOPAR RULES