Rear Diff. 12bolt - The 1947 - Present Chevrolet & GMC Truck Message Board Network

04-21-2003, 08:47 PM

I have a 72' GMC with a 12 bolt rear diff., 3.73 gearing. I just got it three weeks ago, and when I was changing the oil I could see some scratches like on the diff. gear housing or pumpkin inside. Since that I have driven it once. And when I deccelerate, theres a whine sound to it. Then when it heats up, it sounds even worse, like its going to fall out. I need help deciding what all should be changed and replaced, and what gearing I should go to. Does it have to do with the rear diff. that I cannot start my tranny in first, b/c its a granny tranny, or is it the tranny that needs re-geared. Anyone from So Cal. Area that reccommends a diff shop?

busterwivell · 04-21-2003, 08:51 PM

Welcome to the board. I have relatives that live in Ironwood. Can't help with the diff problem. If you need to replace the tranny, I've got a spare. Someone will be able to handle your diff questions shortly.

04-21-2003, 09:23 PM

Hey Busterwivell

Nice to actually know someone from around this area? If you're ever in this area visiting family, stop by and give me some ideas or help. What kind of tranny do you have and how much do you want for it, and what needs to be fixed on it, if any.........thanks

04-21-2003, 09:30 PM

Hey Busterwivell

Nice to actually know someone from around this area? If you're ever in this area visiting family, stop by and give me some ideas or help. What kind of tranny do you have and how much do you want for it, and what needs to be fixed on it, if any.........thanks

knucklebuster · 04-21-2003, 09:37 PM

Check your pinion nut.I ruined a perfectly good rearend once by just ignoring it.You may have to replace ring and pinion if too far gone.

busterwivell · 04-21-2003, 11:46 PM

The tranny I have is the granny geared 4 speed my one ton came with. It's fine, but I converted to a 700R4. Actually, i have the complete changeover, crossmember, steering column, clutch, everything........don't knkow what to do with it, it just takes up space in the garage, but I won't throw it out. Somebody will need it and I'll wind up with some garage space again. Don't know if I'll get back to my sister & brother in law's place till New Years, but who knows!

04-22-2003, 10:28 PM

My Tranny's first gear works fine, but its geared to maybe going from 0mph to 2mph, so I just start out in 2nd. B: You have an extra tranny that is a granny, right? I'm interested in the Crossmember, is the column a tilt?, is it is, I am interested in that too, and whatever else you have for it.

Hooter · 04-23-2003, 01:22 AM

could be your steady bearing also. does it sound like synchros in your tranny are whining?, if there are marks in your rearend, sounds like some bearings and other parts inside are shot, good luck with your repair

04-21-2003, 08:47 PM	#1
Linus0014 Guest Posts: n/a	Rear Diff. 12bolt I have a 72' GMC with a 12 bolt rear diff., 3.73 gearing. I just got it three weeks ago, and when I was changing the oil I could see some scratches like on the diff. gear housing or pumpkin inside. Since that I have driven it once. And when I deccelerate, theres a whine sound to it. Then when it heats up, it sounds even worse, like its going to fall out. I need help deciding what all should be changed and replaced, and what gearing I should go to. Does it have to do with the rear diff. that I cannot start my tranny in first, b/c its a granny tranny, or is it the tranny that needs re-geared. Anyone from So Cal. Area that reccommends a diff shop?

04-21-2003, 08:51 PM	#2
busterwivell Registered User Join Date: Jan 2002 Location: Sahuarita, AZ USA Posts: 2,033	Welcome to the board. I have relatives that live in Ironwood. Can't help with the diff problem. If you need to replace the tranny, I've got a spare. Someone will be able to handle your diff questions shortly. __________________ Bill - Tucson, AZ 47 Chevrolet 2 dr sedan 56 Chevrolet 210 2 dr sedan 66 Chevrolet Malibu 2 dr 4 speed 71 Chevrolet C30 Longhorn 86 Chevrolet Monte Carlo SS (Sold) 01 Chevrolet Tahoe IM - BUSTERWIVE@aol.com

04-21-2003, 09:37 PM	#5
knucklebuster Failure is NOT an option! Join Date: Feb 2003 Location: greenwood s.c. Posts: 811	Check your pinion nut.I ruined a perfectly good rearend once by just ignoring it.You may have to replace ring and pinion if too far gone. __________________ House payment or truck parts?????.........why does life have to be so complicated? 1969 Chevy Shortbed Fleetside 1969 Camaro ps pb a/c(drove in high school now it's just a yard ornament,but it's next on the list for resto) 1990 Ni$$an hardbody( daily beater that has been really beaten!) 1999 Grand Am GT(wifes ride...never buy a pontiac!!Trust Me)

04-21-2003, 11:46 PM	#6
busterwivell Registered User Join Date: Jan 2002 Location: Sahuarita, AZ USA Posts: 2,033	The tranny I have is the granny geared 4 speed my one ton came with. It's fine, but I converted to a 700R4. Actually, i have the complete changeover, crossmember, steering column, clutch, everything........don't knkow what to do with it, it just takes up space in the garage, but I won't throw it out. Somebody will need it and I'll wind up with some garage space again. Don't know if I'll get back to my sister & brother in law's place till New Years, but who knows! __________________ Bill - Tucson, AZ 47 Chevrolet 2 dr sedan 56 Chevrolet 210 2 dr sedan 66 Chevrolet Malibu 2 dr 4 speed 71 Chevrolet C30 Longhorn 86 Chevrolet Monte Carlo SS (Sold) 01 Chevrolet Tahoe IM - BUSTERWIVE@aol.com

04-23-2003, 01:22 AM	#8
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	could be your steady bearing also. does it sound like synchros in your tranny are whining?, if there are marks in your rearend, sounds like some bearings and other parts inside are shot, good luck with your repair __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life

04-21-2003, 09:23 PM	#3
Linus0014 Guest Posts: n/a	Hey Busterwivell Nice to actually know someone from around this area? If you're ever in this area visiting family, stop by and give me some ideas or help. What kind of tranny do you have and how much do you want for it, and what needs to be fixed on it, if any.........thanks

04-21-2003, 09:30 PM	#4
Linus0014 Guest Posts: n/a	Hey Busterwivell Nice to actually know someone from around this area? If you're ever in this area visiting family, stop by and give me some ideas or help. What kind of tranny do you have and how much do you want for it, and what needs to be fixed on it, if any.........thanks

04-22-2003, 10:28 PM	#7
Linus0014 Guest Posts: n/a	My Tranny's first gear works fine, but its geared to maybe going from 0mph to 2mph, so I just start out in 2nd. B: You have an extra tranny that is a granny, right? I'm interested in the Crossmember, is the column a tilt?, is it is, I am interested in that too, and whatever else you have for it.

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