OUCH! My rear end hurts - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**truckster** · 05-16-2008, 09:21 PM

About a week ago I noticed gear oil under my rear differential (72 Blazer 4X4). No big deal, so I parked it. I drove it down to the office and back (about 4 miles total) and parked it again, and today I noticed a lot more gear oil. I pulled off the back cover to replace the gasket, and there was a piece of metal that went partway through the cover. It's about 1/4 by 1/2 inch and less than 1/16 thick. There were more in the bottom of the housing. Any ideas what gives? All of the metal is flat, so I don't think it's a piece of the ring gear or pinion. Maybe a shim? Do I put it back together and drive it?

Also, it's supposed to be a posi, but I don't see any springs or plates. Maybe it's been replaced before - there was some silicone gasket on the inside of the cover, like maybe they plugged a hole before.

I just got the top off and I really want to drive my Blazer, but I don't want to ruin it. Any help is appreciated.

70rs/ss · 05-16-2008, 09:59 PM

If there are metal chunks, that ain't gonna just go away. You need to figure out where the pieces came from and fix it, if you can't do it a rear end shop can. If it is a shim (not sure how one would fly out) but that will mean too much clearance and a fatal break could happen, so i would get it fixed. On a lighter note, sometimes a complete used rear can be had cheaper than a repair or rebuild?

**truckster** · 05-16-2008, 10:42 PM

Looks like I'll need to keep my eyes on the local pick-n-pulls and see if I can find a replacement.

Maybe I'll just close it up in the meantime and drive it, since I don't think this rear is a posi anyway.

northerngmc · 05-16-2008, 10:48 PM

It isn't a c clip or part of a c clip is it?

They can fall out if worn. I had it happen on my 59 GMC. Is so the axle will come right out of the housing.

Pinion shaft on right, C clip in center and axle showing spline and C clip groove

Could one have come out and then went through the gears and been cut into pieces?

**truckdude239** · 05-17-2008, 12:57 AM

a picture would help alot with us telling us whats wrong

**truckster** · 05-17-2008, 05:46 AM

Quote:

Originally Posted by northerngmc

It isn't a c clip or part of a c clip is it?

They can fall out if worn. I had it happen on my 59 GMC. Is so the axle will come right out of the housing.

Could one have come out and then went through the gears and been cut into pieces?

Hmm... it sure looks like it might be. I'll crawl under it tomorrow and check. Thanks. If that's it, I might not be in as bad of shape as I thought.

IvelDesigns · 05-17-2008, 07:30 AM

just don't drive it until you figure out what the issue is. i'd hate to see the axle come out of the housing and send you spinning into a ditch.

**truckster** · 05-17-2008, 08:28 PM

Here are pics. The metal pieces are flat and are .055 thick. The yellow lines point to some of the holes in the cover. The yellow circle has some of the pieces in it.

I'm also curious to know what kind of differential this is.

Thanks for your help.

**Yukon Jack** · 05-17-2008, 08:55 PM

Definitely figure out what is going on before driving it anymore. You could end up in a ditch if something failed or worse, you could kill someone if it failed and you lost control.

**truckdude239** · 05-17-2008, 09:18 PM

that looks like a posi unit

jayharrell · 05-17-2008, 09:27 PM

posi for sure

Did you know it was a posi??

LONGHAIR · 05-17-2008, 10:25 PM

That's not just any posi....That is a "Gov-Lock". They are well known for scattering parts, though it is usually the little gear parts. That looks like some of the seperator plate parts from the clutches.
Be aware that it is now totally junk. You may be able to get parts for it, but dont watse your time/money.
If that red sealer smear was already there, someone else has already grenaded it and knows it. The simplest and most cost effective way to fix this is to find a good "complete" rear end. Salvage, Craigslist, etc.
If you go that route, be sure to open it up and look inside before you buy. Avoid another "Gov-Lock", look for an open or "regular" posi unit. The parts with the arrows will indicate the "Gov-Lock" indicators, a "regular" Posi doesn't have them. The top two are the governor wheels. The bottom arrow points to where you will see some small gear teeth, behind the side gear.
These are "Gov-lock" parts, a regular posi will just have flat plates with coils springs between them wedged in the side gears.

**truckster** · 05-17-2008, 10:42 PM

Quote:

Originally Posted by jayharrell

posi for sure

Did you know it was a posi??

I thought it was.

I have a new post about it. It's in bad shape.

jayharrell · 05-18-2008, 01:20 AM

gov posi.. never heard of them. the pic did seem weird though. This is all that i've ever seen of a reg posi.

Only reason i ask is i've seen 2 or 3 guys stumble across a posi on here. I'm going to crack mine tonight to check the ratio #s on the gear and maybe get lucky. LOL...

Any advantage to having a gov posi in a 4wd?? Does it stay locked untill a higher RPM or does it stay unlocked unitll a higher RPM??

LONGHAIR · 05-18-2008, 02:52 AM

jayharrell,
I never does "lock" that's an optimistic marketing type name. It is a clutch-type unit that has "variable" pressure applied to them. It is supposed to act like an "open" differential until one wheel spins a certain amout faster than the other. Then the pressure is applied to the clutches. The little teeth on the gear (bottom arrow) spin the shaft (upper arrow) which makes all of that happen.
I have heard that they are not too bad in the big 14bolt Full-Floater axles, but in the 10 and 12 they just won't last with any performance up-grades. More power and/or bigger tires can kill them pretty quickly.

05-16-2008, 09:21 PM	#1
truckster Senior Member Join Date: Jan 2001 Location: Orem, Utah Posts: 7,799	OUCH! My rear end hurts About a week ago I noticed gear oil under my rear differential (72 Blazer 4X4). No big deal, so I parked it. I drove it down to the office and back (about 4 miles total) and parked it again, and today I noticed a lot more gear oil. I pulled off the back cover to replace the gasket, and there was a piece of metal that went partway through the cover. It's about 1/4 by 1/2 inch and less than 1/16 thick. There were more in the bottom of the housing. Any ideas what gives? All of the metal is flat, so I don't think it's a piece of the ring gear or pinion. Maybe a shim? Do I put it back together and drive it? Also, it's supposed to be a posi, but I don't see any springs or plates. Maybe it's been replaced before - there was some silicone gasket on the inside of the cover, like maybe they plugged a hole before. I just got the top off and I really want to drive my Blazer, but I don't want to ruin it. Any help is appreciated.

05-16-2008, 09:59 PM	#2
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: OUCH! My rear end hurts If there are metal chunks, that ain't gonna just go away. You need to figure out where the pieces came from and fix it, if you can't do it a rear end shop can. If it is a shim (not sure how one would fly out) but that will mean too much clearance and a fatal break could happen, so i would get it fixed. On a lighter note, sometimes a complete used rear can be had cheaper than a repair or rebuild?

05-16-2008, 10:42 PM	#3
truckster Senior Member Join Date: Jan 2001 Location: Orem, Utah Posts: 7,799	Re: OUCH! My rear end hurts Looks like I'll need to keep my eyes on the local pick-n-pulls and see if I can find a replacement. Maybe I'll just close it up in the meantime and drive it, since I don't think this rear is a posi anyway.

05-16-2008, 10:48 PM	#4
northerngmc Registered User Join Date: Jan 2004 Location: Whitehorse YK Canada Posts: 2,651	Re: OUCH! My rear end hurts It isn't a c clip or part of a c clip is it? They can fall out if worn. I had it happen on my 59 GMC. Is so the axle will come right out of the housing. Pinion shaft on right, C clip in center and axle showing spline and C clip groove Could one have come out and then went through the gears and been cut into pieces? __________________ Blaine 59 GMC 9314 a.k.a. Whoopee 68 C20 50th Anniversary a.k.a. The Rat http://www.flickr.com/photos/northerngmc/ http://www.members.tripod.com/P-wee/index_032.htm 1.61803 is one H of a lot better than 3.14159, no really it is!

05-17-2008, 12:57 AM	#5
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,217	Re: OUCH! My rear end hurts a picture would help alot with us telling us whats wrong __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

05-17-2008, 07:30 AM	#7
IvelDesigns Commander Taco Bello Join Date: Sep 2006 Location: Des Moines, Iowa Posts: 2,232	Re: OUCH! My rear end hurts just don't drive it until you figure out what the issue is. i'd hate to see the axle come out of the housing and send you spinning into a ditch. __________________ Bagged '50 3600 - Bumper punchin' road kill since 2009... Bagged '69 C10 Longbed - Bumper punchin' road kill since 2007...

05-17-2008, 08:28 PM	#8
truckster Senior Member Join Date: Jan 2001 Location: Orem, Utah Posts: 7,799	Re: OUCH! My rear end hurts - updated with pics Here are pics. The metal pieces are flat and are .055 thick. The yellow lines point to some of the holes in the cover. The yellow circle has some of the pieces in it. I'm also curious to know what kind of differential this is. Thanks for your help. Attached Images Last edited by truckster; 05-17-2008 at 08:29 PM.

05-17-2008, 08:55 PM	#9
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,683	Re: OUCH! My rear end hurts Definitely figure out what is going on before driving it anymore. You could end up in a ditch if something failed or worse, you could kill someone if it failed and you lost control. __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14

05-17-2008, 09:18 PM	#10
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,217	Re: OUCH! My rear end hurts that looks like a posi unit __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

05-17-2008, 09:27 PM	#11
jayharrell Gettin By on Gettin By Join Date: Jan 2008 Location: Cedar Creek, Tx Posts: 1,033	Re: OUCH! My rear end hurts posi for sure Did you know it was a posi?? __________________ 69 CST10 LWB 455 Buick 00 S10 2.2 Vin5 76 GL1000 Naked 1bl VW carb "Adios to all the concrete; Gonna get me some dirt road back streets"

05-17-2008, 10:25 PM	#12
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: OUCH! My rear end hurts That's not just any posi....That is a "Gov-Lock". They are well known for scattering parts, though it is usually the little gear parts. That looks like some of the seperator plate parts from the clutches. Be aware that it is now totally junk. You may be able to get parts for it, but dont watse your time/money. If that red sealer smear was already there, someone else has already grenaded it and knows it. The simplest and most cost effective way to fix this is to find a good "complete" rear end. Salvage, Craigslist, etc. If you go that route, be sure to open it up and look inside before you buy. Avoid another "Gov-Lock", look for an open or "regular" posi unit. The parts with the arrows will indicate the "Gov-Lock" indicators, a "regular" Posi doesn't have them. The top two are the governor wheels. The bottom arrow points to where you will see some small gear teeth, behind the side gear. These are "Gov-lock" parts, a regular posi will just have flat plates with coils springs between them wedged in the side gears. Attached Images Last edited by LONGHAIR; 05-17-2008 at 10:26 PM.

05-18-2008, 01:20 AM	#14
jayharrell Gettin By on Gettin By Join Date: Jan 2008 Location: Cedar Creek, Tx Posts: 1,033	Re: OUCH! My rear end hurts gov posi.. never heard of them. the pic did seem weird though. This is all that i've ever seen of a reg posi. Only reason i ask is i've seen 2 or 3 guys stumble across a posi on here. I'm going to crack mine tonight to check the ratio #s on the gear and maybe get lucky. LOL... Any advantage to having a gov posi in a 4wd?? Does it stay locked untill a higher RPM or does it stay unlocked unitll a higher RPM?? Attached Images __________________ 69 CST10 LWB 455 Buick 00 S10 2.2 Vin5 76 GL1000 Naked 1bl VW carb "Adios to all the concrete; Gonna get me some dirt road back streets" Last edited by jayharrell; 05-18-2008 at 01:21 AM.

05-18-2008, 02:52 AM	#15
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: OUCH! My rear end hurts jayharrell, I never does "lock" that's an optimistic marketing type name. It is a clutch-type unit that has "variable" pressure applied to them. It is supposed to act like an "open" differential until one wheel spins a certain amout faster than the other. Then the pressure is applied to the clutches. The little teeth on the gear (bottom arrow) spin the shaft (upper arrow) which makes all of that happen. I have heard that they are not too bad in the big 14bolt Full-Floater axles, but in the 10 and 12 they just won't last with any performance up-grades. More power and/or bigger tires can kill them pretty quickly.



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