Rear diff issues - The 1947 - Present Chevrolet & GMC Truck Message Board Network

evan · 10-15-2007, 01:09 AM

Lately I've been having some issues with the rear diff in my 78. It operates normally 95% of the time but every once in a while it locks the two wheels together and doesn't allow the outside tire to turn faster around corners.

Is this a common symptom of a dying rear end? When it gets worse will it just stay locked in the no-slip mode or will it cause both rear wheels to lock up (stop spinning) while I'm cruising down the road? Without pulling the cover off, is it possible for you to be pretty sure of what needs replacing?

MylilBowTie · 10-16-2007, 08:13 AM

Its just guessing not pulling the cover off. Its not that bad of a job to pull just smelly.

evan · 10-16-2007, 09:14 AM

Quote:

Originally Posted by MylilBowTie

Its just guessing not pulling the cover off. Its not that bad of a job to pull just smelly.

OK, tomorrow's my day off so I'll see what I can see.

hiway · 10-16-2007, 11:09 AM

Change the oil and also put the GM limited slip additive in it. Do a few tight circles in each direction to work it in. (Assumming the inspection doesn't look bad)

f.monroe · 10-16-2007, 05:52 PM

Sounds like a GovLoc rear instead of a clutch type posi . I would say change the fluid but also make sure the tires are the same size and properly inflated . That can cause it to lock up and if there is a different diameter tire issue , it wont unlock correctly . Frank

evan · 10-16-2007, 07:19 PM

Thanks guys. I keep a close eye on tire pressures and they are all the same size. It's the stock open rear diff so will that GM limited slip additive still help?

77 350 Shorty Wide · 10-16-2007, 08:07 PM

If your sure it's an open carrrier, the additive will do nothing really. If indeed you have an open carrier about the only answer then is... FOD (Foreign Object Debris) floating around inside getting between the moving parts locking things up. This happened to a buddy of mine in his '55 Belair back in 76, wasn't pretty at all. He was doing between 20 & 30 when it completely locked up. Pretty scary ride for about 30 seconds untill all motion ceased.
Wish you the best & be very careful driving, I would get it fixed asap.

Terry

evan · 10-17-2007, 07:25 PM

Quote:

Originally Posted by 77 350 Shorty Wide

If your sure it's an open carrrier, the additive will do nothing really. If indeed you have an open carrier about the only answer then is... FOD (Foreign Object Debris) floating around inside getting between the moving parts locking things up. This happened to a buddy of mine in his '55 Belair back in 76, wasn't pretty at all. He was doing between 20 & 30 when it completely locked up. Pretty scary ride for about 30 seconds untill all motion ceased.
Wish you the best & be very careful driving, I would get it fixed asap.

Terry

Actually that's exactly what my buddy said would happen and why I started the thread. Sounds like a shocking experience.

I pulled the cover off today but unfortunately my camera died when I tried to take the first picture of the internals. I inspected it pretty carefully but couldn't find any blatant problems. I was told to expect small metal shavings kind of like the fine stuff left behind by an eraser and I did but I also found 8 larger pieces.

Do you think those are big enough to have been the ones that were causing the problem? I took it around the block and everything was fine so far.

Pyrotechnic · 10-17-2007, 07:38 PM

That is NOT good.

bigblock79 · 10-17-2007, 07:50 PM

looks like you got some tooth missing on the ring gear

f.monroe · 10-17-2007, 10:07 PM

Everything in the rear diff is necessary and the metal pictured came from somewhere . No matter where that was , it aint good . Frank

MylilBowTie · 10-17-2007, 10:48 PM

I'm thinking it may be the spider gears starting to go. It would have been nice to get a picture of the inside. They sell a kit to replace those. I believe it comes with the spider gears, bearings, shaft and bolt.

evan · 10-18-2007, 12:39 AM

I was thinking about upgrading to a posi. Would doing that replace my currently broken parts, or would that be something different entirely?

**Captkaos** · 10-18-2007, 11:01 AM

As long as you ring gear and pinion are ok, the limited slip will fix the problem. If there are pieces missing from them I HIGHLY recommend fixing them also.

It looks like spider gears to me also.

evan · 10-19-2007, 09:01 PM

It was fine until tonight. It locked the two wheels together again. I guess I'll have to look into upgrades.

I'm considering the Moser eaton posi unit, unless somebody has a reason to avoid them.

evan · 10-26-2007, 05:36 PM

Do I need a 30 spline unit???

10-15-2007, 01:09 AM	#1
evan Registered User Join Date: Jul 2005 Location: SK, Canada Posts: 488	Rear diff issues Lately I've been having some issues with the rear diff in my 78. It operates normally 95% of the time but every once in a while it locks the two wheels together and doesn't allow the outside tire to turn faster around corners. Is this a common symptom of a dying rear end? When it gets worse will it just stay locked in the no-slip mode or will it cause both rear wheels to lock up (stop spinning) while I'm cruising down the road? Without pulling the cover off, is it possible for you to be pretty sure of what needs replacing? __________________ Evan B.

10-16-2007, 08:13 AM	#2
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	Re: Rear diff issues Its just guessing not pulling the cover off. Its not that bad of a job to pull just smelly. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

10-16-2007, 11:09 AM	#4
hiway Mad Scientist Join Date: Jul 2005 Location: Enola Arkansas Posts: 380	Re: Rear diff issues Change the oil and also put the GM limited slip additive in it. Do a few tight circles in each direction to work it in. (Assumming the inspection doesn't look bad) __________________ Everythang relates to Beer! 86 1/2ton on tons! sbc/465/208/D60/14/35's 81 Postal....with 468 bbc 97 Merc Marq comuter 07 Suburban 02 Danger Ranger

10-16-2007, 05:52 PM	#5
f.monroe Senior Member Join Date: May 2004 Location: Caldwell,Tx. Posts: 3,648	Re: Rear diff issues Sounds like a GovLoc rear instead of a clutch type posi . I would say change the fluid but also make sure the tires are the same size and properly inflated . That can cause it to lock up and if there is a different diameter tire issue , it wont unlock correctly . Frank __________________ Born and proudly residing in a Red State !

10-16-2007, 07:19 PM	#6
evan Registered User Join Date: Jul 2005 Location: SK, Canada Posts: 488	Re: Rear diff issues Thanks guys. I keep a close eye on tire pressures and they are all the same size. It's the stock open rear diff so will that GM limited slip additive still help? __________________ Evan B.

10-16-2007, 08:07 PM	#7
77 350 Shorty Wide Registered User Join Date: Dec 2006 Location: Yakima, WA Posts: 325	Re: Rear diff issues If your sure it's an open carrrier, the additive will do nothing really. If indeed you have an open carrier about the only answer then is... FOD (Foreign Object Debris) floating around inside getting between the moving parts locking things up. This happened to a buddy of mine in his '55 Belair back in 76, wasn't pretty at all. He was doing between 20 & 30 when it completely locked up. Pretty scary ride for about 30 seconds untill all motion ceased. Wish you the best & be very careful driving, I would get it fixed asap. Terry

10-17-2007, 07:38 PM	#9
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: Rear diff issues That is NOT good.

10-17-2007, 07:50 PM	#10
bigblock79 67 Chevy Stepside Join Date: Mar 2007 Location: Jonesville NC Posts: 836	Re: Rear diff issues looks like you got some tooth missing on the ring gear __________________ 1967 Chevy stepside 1976 BIG DOOLEY 454 turbo 400 4:11

10-17-2007, 10:07 PM	#11
f.monroe Senior Member Join Date: May 2004 Location: Caldwell,Tx. Posts: 3,648	Re: Rear diff issues Everything in the rear diff is necessary and the metal pictured came from somewhere . No matter where that was , it aint good . Frank __________________ Born and proudly residing in a Red State !

10-17-2007, 10:48 PM	#12
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	Re: Rear diff issues I'm thinking it may be the spider gears starting to go. It would have been nice to get a picture of the inside. They sell a kit to replace those. I believe it comes with the spider gears, bearings, shaft and bolt. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

10-18-2007, 12:39 AM	#13
evan Registered User Join Date: Jul 2005 Location: SK, Canada Posts: 488	Re: Rear diff issues I was thinking about upgrading to a posi. Would doing that replace my currently broken parts, or would that be something different entirely? __________________ Evan B.

10-18-2007, 11:01 AM	#14
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Re: Rear diff issues As long as you ring gear and pinion are ok, the limited slip will fix the problem. If there are pieces missing from them I HIGHLY recommend fixing them also. It looks like spider gears to me also. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

10-19-2007, 09:01 PM	#15
evan Registered User Join Date: Jul 2005 Location: SK, Canada Posts: 488	Re: Rear diff issues It was fine until tonight. It locked the two wheels together again. I guess I'll have to look into upgrades. I'm considering the Moser eaton posi unit, unless somebody has a reason to avoid them. __________________ Evan B. Last edited by evan; 10-20-2007 at 12:40 AM.

10-26-2007, 05:36 PM	#16
evan Registered User Join Date: Jul 2005 Location: SK, Canada Posts: 488	Re: Rear diff issues Do I need a 30 spline unit??? __________________ Evan B.



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