1972 GMC rear end help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

90four5spd · 07-16-2014, 09:32 AM

Hello everyone. I recently purchased a 1972 GMC project truck that the rear end is very noisy , even at low speeds. There are several pull-your-part type places around here that have many 73-86 trucks I could pick up a cheap rear end from, but need help with what rear ends would work without having to weld new spring perches/shock mounts. I did use the search button, but had no luck with finding the information I'm looking for. Any help would be appreciated. Thank you!

boostedc10 · 07-16-2014, 09:47 AM

I am not aware of any "direct" swap axles for our trucks outside of the body style. You will have to change the perches and shock tabs.

**michael bustamante** · 07-16-2014, 12:06 PM

Well most gmc are leaf spring right. So couldnt a 73+rear end bolt right in?

Oldtruckfanatic · 07-16-2014, 12:13 PM

They bolt in if Its leaf but those odd shock mounts with one forward and one back dont work without changing things.

davepl · 07-16-2014, 01:09 PM

If you're not a welder, I'd stick with finding one from the same year.

Have you checked the fluid level? Rear ends don't usually drift out of spec, they're usually set up right or set up wrong from get go.

There might be a "mechanic in a can" product that will quiet it down. I don't usually advocate that, but if you're next option is to replace the axle, why not?

sKnNyPpY · 07-16-2014, 01:21 PM

New fluid and limited slip additive if that's what ya got. Start there and drive it till it drops.

70blackfish · 07-16-2014, 01:46 PM

get the one you have fixed

90four5spd · 07-16-2014, 05:58 PM

Sorry for not giving some of the important information, but yes it is a leaf spring rear end. I am looking for the least expensive option, as I'm building up a rear coil spring frame for the truck while I am driving the GMC leaf spring frame. I just need something to get me by for now. I'm just curious if anyone has tried to install a 73-86 rear end into a 67-72 GMC leaf spring frame. Thanks for eveyones input

Gimme Jimmy · 07-23-2014, 06:00 PM

Can I assume that you have a 1/2 ton leaf spring truck? If so, any 1/2 ton leaf spring axle from '67 to '72 is a direct fit ('71 and '72 have a 5 bolt pattern, same as the large GM cars) 4wd models use 6 bolt. The later axles ('73-on, 5 bolt) will fit, but the spring pads will require some grinding as the newer trucks have wider leaves. If you are using a newer axle you may be able to use your 6 bolt axles and drums in it (compare the parts b4 trying this). Both Chevy and GMC used both leaf and coil rear ends in any given year. The old wives tale has it that Chevy always used coils and GMC used leaves is BOGUS! either make can have either system.

**LockDoc** · 07-23-2014, 10:53 PM

Quote:

Originally Posted by Gimme Jimmy

Can I assume that you have a 1/2 ton leaf spring truck? If so, any 1/2 ton leaf spring axle from '67 to '72 is a direct fit ('71 and '72 have a 5 bolt pattern, same as the large GM cars) 4wd models use 6 bolt. The later axles ('73-on, 5 bolt) will fit, but the spring pads will require some grinding as the newer trucks have wider leaves. If you are using a newer axle you may be able to use your 6 bolt axles and drums in it (compare the parts b4 trying this). Both Chevy and GMC used both leaf and coil rear ends in any given year. The old wives tale has it that Chevy always used coils and GMC used leaves is BOGUS! either make can have either system.

Actually in '67-'72 Chevy's came stock with coils with leafs listed as an option and GMC's came stock with leafs with coils listed as an option, so you are correct in saying that they could have either one, but only if ordered with the option.

LockDoc

Prescott · 07-23-2014, 11:06 PM

My '67 was making a bunch of noise from the rear end, and I was sure it was going to cost me a fortune. It turned out to be a bad drive shaft support bearing (some call a carrier bearing). I rebuilt the whole drive shaft with a new bearing and three new u-joints for around 50 bucks in parts. Cured.

I'm not saying that this is the problem with your truck, but it might save you a lot to check your drive shaft first.

**davischevy** · 04-11-2017, 10:16 PM

I had the pinion nut loosen once. It sounded like it was going to come apart.

**davischevy** · 04-11-2017, 10:18 PM

Sorry, I was in search mode, ran on to this and had a senior moment. I forgot it was old news.

GASoline71 · 04-12-2017, 12:07 PM

Quote:

Originally Posted by 70blackfish

get the one you have fixed

Yup... used 40+ year old rear ends are a crap shoot.

Gary

07-16-2014, 09:32 AM	#1
90four5spd Registered User Join Date: Sep 2003 Location: Oklahoma City, OK Posts: 6	1972 GMC rear end help Hello everyone. I recently purchased a 1972 GMC project truck that the rear end is very noisy , even at low speeds. There are several pull-your-part type places around here that have many 73-86 trucks I could pick up a cheap rear end from, but need help with what rear ends would work without having to weld new spring perches/shock mounts. I did use the search button, but had no luck with finding the information I'm looking for. Any help would be appreciated. Thank you!

07-16-2014, 09:47 AM	#2
boostedc10 Registered User Join Date: Oct 2012 Location: Detroit Posts: 748	Re: 1972 GMC rear end help I am not aware of any "direct" swap axles for our trucks outside of the body style. You will have to change the perches and shock tabs.

07-16-2014, 12:06 PM	#3
michael bustamante Senior Member Join Date: Sep 2007 Location: Albuquerque NM Posts: 7,862	Re: 1972 GMC rear end help Well most gmc are leaf spring right. So couldnt a 73+rear end bolt right in? __________________ 1967custom

07-16-2014, 12:13 PM	#4
Oldtruckfanatic Truck junkie Join Date: May 2006 Location: Reno NV Posts: 697	Re: 1972 GMC rear end help They bolt in if Its leaf but those odd shock mounts with one forward and one back dont work without changing things.

07-16-2014, 01:09 PM	#5
davepl Registered User Join Date: Aug 2006 Location: Redmond, WA Posts: 6,332	Re: 1972 GMC rear end help If you're not a welder, I'd stick with finding one from the same year. Have you checked the fluid level? Rear ends don't usually drift out of spec, they're usually set up right or set up wrong from get go. There might be a "mechanic in a can" product that will quiet it down. I don't usually advocate that, but if you're next option is to replace the axle, why not? __________________ 1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible

07-16-2014, 01:21 PM	#6
sKnNyPpY Registered User Join Date: Sep 2012 Location: Columbia, SC Posts: 549	Re: 1972 GMC rear end help New fluid and limited slip additive if that's what ya got. Start there and drive it till it drops. __________________ Life is too long to go slow... 71 GMC 1500 Super Custom LWB 350/350 AC(replaced w/vintage air)/PS/PB 2.5 CPP Spindle, 1" CPP Drop Spring, CPP Front and Rear Sway Bars/DJM Flip, new General Spring KC 5 spring pack, HEI /IntReg Alt 20x8.5 OldSkools 5" BS, 275/45 Falkens

07-16-2014, 01:46 PM	#7
70blackfish Registered User Join Date: Oct 2012 Location: Newhall CA Posts: 1,195	Re: 1972 GMC rear end help get the one you have fixed __________________ 69 SWB 780hp Hellcat powered, manual 6 speed, currie 9

07-16-2014, 05:58 PM	#8
90four5spd Registered User Join Date: Sep 2003 Location: Oklahoma City, OK Posts: 6	Re: 1972 GMC rear end help Sorry for not giving some of the important information, but yes it is a leaf spring rear end. I am looking for the least expensive option, as I'm building up a rear coil spring frame for the truck while I am driving the GMC leaf spring frame. I just need something to get me by for now. I'm just curious if anyone has tried to install a 73-86 rear end into a 67-72 GMC leaf spring frame. Thanks for eveyones input Last edited by 90four5spd; 07-16-2014 at 06:18 PM.

07-23-2014, 06:00 PM	#9
Gimme Jimmy Registered User Join Date: Jan 2014 Location: Aloha, Or. Posts: 46	Re: 1972 GMC rear end help Can I assume that you have a 1/2 ton leaf spring truck? If so, any 1/2 ton leaf spring axle from '67 to '72 is a direct fit ('71 and '72 have a 5 bolt pattern, same as the large GM cars) 4wd models use 6 bolt. The later axles ('73-on, 5 bolt) will fit, but the spring pads will require some grinding as the newer trucks have wider leaves. If you are using a newer axle you may be able to use your 6 bolt axles and drums in it (compare the parts b4 trying this). Both Chevy and GMC used both leaf and coil rear ends in any given year. The old wives tale has it that Chevy always used coils and GMC used leaves is BOGUS! either make can have either system.

07-23-2014, 11:06 PM	#11
Prescott Registered User Join Date: Jun 2013 Location: Prescott AZ Posts: 31	Re: 1972 GMC rear end help My '67 was making a bunch of noise from the rear end, and I was sure it was going to cost me a fortune. It turned out to be a bad drive shaft support bearing (some call a carrier bearing). I rebuilt the whole drive shaft with a new bearing and three new u-joints for around 50 bucks in parts. Cured. I'm not saying that this is the problem with your truck, but it might save you a lot to check your drive shaft first.

04-11-2017, 10:16 PM	#12
davischevy Senior Member Join Date: Sep 2008 Location: Harrison, Arkansas Posts: 9,860	Re: 1972 GMC rear end help I had the pinion nut loosen once. It sounded like it was going to come apart. __________________ other Larry Build thread, Arkansas K10 https://67-72chevytrucks.com/vboard/...=755797&page=5 The ability to speak several languages is an asset, but the ability to keep your mouth shut in any language is priceless.

04-11-2017, 10:18 PM	#13
davischevy Senior Member Join Date: Sep 2008 Location: Harrison, Arkansas Posts: 9,860	Re: 1972 GMC rear end help Sorry, I was in search mode, ran on to this and had a senior moment. I forgot it was old news. __________________ other Larry Build thread, Arkansas K10 https://67-72chevytrucks.com/vboard/...=755797&page=5 The ability to speak several languages is an asset, but the ability to keep your mouth shut in any language is priceless.



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