Gentlemen, and ladies. I need HELP. I have a '79 auto that just moans, groans and pops from the rear. This car sat ten years before I got it about 500 miles ago. It gets worse when the rear heats up. It also makes a grinding moaning noise in turns but seems fine 15mph and over. It has 75K on the OD. I have removed the short shafts and lubed the U joints, they appeard to be fine. I rolled the wheels around with the shafts out and they appeard to be fine. I can't tell if it needs the weight on it to give it the strees I need to duplicate the damage being caused or if it is just the Differential? I'm ready to fix the thing but I hope I don't have to rebuild the entire rear end before I find it. Every bolt is tight back there, any suggestions? moaner groaner in Hawaii
-
-
Re: Rear end Woes
I had a similar, but it sounds like maybe less severe problem. I posted a message much like yours about 18 months ago. Of course the experts here answered my distress call gave me some advice, and it did the trick in my case. It is now my pleasure to pass this wisdom along to you. What I was advised to do was a 3 step process:
1. Drain the differential fluid. Well, drain isn't exactly the right word, you need to suck or siphon the juice out of the fill plug. Anyway, get the old fluid out of there. I purchased a suction gun (plews brand) and removed the old gunk.
2. Replace the fluid (I used the GM fluid the first time, but switched to Red Line synthetic this year.
3. When adding positraction additive (friction modifier), double up on it. When using GM fluid I added two bottles, and with the Red Line (which already contains friction moodifier) I added another bottle.
4. Take the car out to a parking lot somewhere and slowly drive in circles, alternating directions.
That was it - theory here is that after long storage periods, the positraction clutch plates stick and grab, causing chatter or other noises. New juice and extra friction modifier cleanse and lubricate the clutch plates, hopefully freeing them enough to make the noise go away. If this doesn't do it for you, a rebuild may be in order but this might be a pretty simple and cheap way out. Worth a try. Your symptoms sound worse than mine and perhaps the prognosis is not as good but it sure is worth a try IMHO. Good luck and let us know how you make out. -
Re: Rear end Woes
Martin, Mike gives good advice. I recently had my differential rebuilt and, for the first time, I saw the positraction plates. There are quite a few thin plates, stacked on top of each other. If a car has sat for quite a while, it is very possible that these positraction units will get gummed up. A complete drain and refill is a quick,cheap insurance policy before you decide to take out and rebuild the diff. GaryComment
-
test for rear end clutches sticking
I have had problems with fluid in the past. I have also blown the rear end out of my car twice (being over enthusiastic), so I have a local gear expert for a friend. He told me to go to a parking lot, lock the steering wheel in one direction, drive a complete circle, lock the steering in the other direction, drive a complete circle, repeat once or twice. If the noise goes away, change the fluid to make the fix permanent. If the spider gears are broken, or the yokes are worn (is one closer to the housing than the other?), it makes a similar sound that doesn't go away. That's why I have two spare rear ends and an additional 3.36 ring and pinion for back up. - DaveComment
-
Re: Rear end Woes
i would also recommend amsoil gear oil for posi as back in my racing days it was the only lube that would let the posi and gears live in corvettes. i use it in my C2500 ext cab and for 80,000 miles the posi has been trouble free.
Comment
-
Re: Rear end Woes
79s were the worst for grinding up the ends of the yokes and spitting the metal out into the rearend. I assume you have checked for this, but sometimes the two conditions are related. If the u bolts on the yokes have hit the rear housing or the dust shield is scraping the housing then there is another problem to attend to. They get so bad that allignment of the rear is sometimes impossible.Comment
Comment