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Old 09-13-2010, 09:12 AM
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Default Help Diagnose Trans or Rear End sound...

I have a 95 Blazer, 4.3, 3 button 4wd, 4dr LT model. This Blazer is old and been abused in its previous life. I have 230,000 miles on it, and it runs good. I have done some major front end work, but am aware that it needs shocks in the back but haven't gotten around to doing it yet. The trans has been drained, filter changed, and Dexron 6 installed about 15,000 miles ago. The vehicle is not throwing a CEL, and while the trans has shifted a little slowly it has never been a problem.

A week ago I started noticing it was almost slipping when going 40 mph or so while in OD. It wasn't a major slip, almost like it was jumping up and down out of OD for a second. On the interstate I began to hear a sound similar to the sound a tire makes when it hits a rumble strip, only a little muffled, and it lasts for a couple of seconds then goes away. I can recreate the sound on limited basis when doing 60-65 and give it gas. It never actually slips, but from time to time does the shift up and down I described. I have also tried putting it in 4wd and it made the same sound, as well as in OD and in Drive.

I know this is very vague, but I need some help to further diagnose what the problem may be and what else to look at. I have checked the trans fluid and its still clean and smells ok.

If anyone can give me some direction on where to look and what to check, I would appreciate it. Again sorry for the vagueness of the post....I tried to search but I never found anything specific.
2001 Oldsmobile Bravada
Old 09-13-2010, 10:37 AM
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have you checked the fluid in the transfer case and the fluid in the rear diff?
Old 09-23-2010, 12:52 PM
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Originally Posted by Ryanmatt135 View Post
have you checked the fluid in the transfer case and the fluid in the rear diff?
Sorry for the delay in responding. All fluid levels are fine. A little dirty but not bad and no visable metal flakes.

I can give more info on the problem. It seems to be RPM dependent. When its around 2000-2300 RPMs its doing almost a little tranmission surging when going slower, say 30-45 mph. You can tell its the tranny and its not a full slip but more of a surge.

When on the interstate, doing 65-75, when its at those RPMs and starts to go up a hill in OD, if it doesnt downshift it will make a sound that reminds you of a tire hitting a rumble strip. Not super loud, but its got some volume. I tried to record it with my phone but its hard to hear. When you give it gas and it downshifts, then it goes away. By not going in OD, it runs at a higher RPM so it doesnt do it, but when the RPM's hit that level it does the surging even when not in OD, so I don't think its a particular gear problem.

Also, I have begun to notice the smell of tranny fluid when I get out after driving it. There is no tranny fluid on the ground but its just a smell of it.

I am somewhat confident its in the tranny, but would like someone to give me their thoughts on it.

Thanks again!
2001 Oldsmobile Bravada
Old 10-08-2010, 05:54 PM
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Ok, I think I might have narrowed it down to the torque converter. All fluids are good. I changed the tranny fluid last fall and used Dexron 6 and it has not been an issue until the recent problems. I think the sound I am hearing (rumblestrip) is the converter not locking up.

Is there a better way to test this?
2001 Oldsmobile Bravada
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1998, 4wd, 97, 99, blazer, chevy, diagnose, differential, end, od, rear, rumble, sound, tires, trans

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