dual master, rear end, and spring questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

F-85 · 07-17-2010, 03:11 PM

Hey Guys

Just got a 65 GMC short/step. All stock. Im gonna end up beefing it up alittle. I have a few questions.

Its got manual drums all around. I wanna put a dual master on it. What do i need?

Its got a 10 bolt rear. I wanna beef that up, or swap it. I also want posi. Any ideas?

I also wanna lower the front alittle. 2" or so. Whats the difference between doing drop springs, or drop spindles?

Josh

raycow · 07-17-2010, 05:43 PM

If you have a GMC with leaf springs your "10 bolt" rear is most likely a Dana 44 unless it has a round cover. For an upgrade keeping the 6 lug pattern, you could go to a 12 bolt off a 4WD Chevy (not GMC), but there won't be a huge increase in strength over the Dana. The next step up would be a 14 bolt semi-floating from an 88-98 light duty 3/4 ton. This will be a couple of inches wider than your stock rear, but totally doable if you order your wheels with appropriate backspacing. Stock (5.5" or so) wheels will usually work as-is.

All else being equal, I like drop spindles better than springs because you won't lose any suspension travel.

For your dual MC and booster you can use a 67-70, as these still had drums all around. However, if you get drop spindles you will need to convert to discs. I don't believe anyone is making drum drop spindles any more.

Ray

**Captainfab** · 07-17-2010, 10:58 PM

Ray is pretty much spot on. Although the GMC 4x4's did have the 12 bolts from 1963 to 1980 as well as the 8.5 10 bolts after about 1980-81. I would suggest trying to find one from a 1976 or newer since they had a little bigger brakes.

If you plan on staying with 4 wheel drums, the '67-'70 master cylinder will work for you. If you convert to discs up front then a '71-'98 master cylinder will work....with a brake booster. The '71-'75's were available with manual brakes.

F-85 · 07-19-2010, 08:49 AM

Im just gonna leave the drums. Ill get one of the 67-70 Masters.

Has anyone used a Powertrax in one of these stock rears? Any other rear end options?

raycow · 07-19-2010, 12:46 PM

For street driving I like the TrueTrac. It is smooth, noiseless, and doesn't require special lube. One to stay away from is the Gov-lock. Engagement can be violent and unpredictable.

Ray

07-17-2010, 03:11 PM	#1
F-85 Registered User Join Date: Jul 2010 Location: Paw Paw,il Posts: 389	dual master, rear end, and spring questions Hey Guys Just got a 65 GMC short/step. All stock. Im gonna end up beefing it up alittle. I have a few questions. Its got manual drums all around. I wanna put a dual master on it. What do i need? Its got a 10 bolt rear. I wanna beef that up, or swap it. I also want posi. Any ideas? I also wanna lower the front alittle. 2" or so. Whats the difference between doing drop springs, or drop spindles? Josh

07-17-2010, 05:43 PM	#2
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: dual master, rear end, and spring questions If you have a GMC with leaf springs your "10 bolt" rear is most likely a Dana 44 unless it has a round cover. For an upgrade keeping the 6 lug pattern, you could go to a 12 bolt off a 4WD Chevy (not GMC), but there won't be a huge increase in strength over the Dana. The next step up would be a 14 bolt semi-floating from an 88-98 light duty 3/4 ton. This will be a couple of inches wider than your stock rear, but totally doable if you order your wheels with appropriate backspacing. Stock (5.5" or so) wheels will usually work as-is. All else being equal, I like drop spindles better than springs because you won't lose any suspension travel. For your dual MC and booster you can use a 67-70, as these still had drums all around. However, if you get drop spindles you will need to convert to discs. I don't believe anyone is making drum drop spindles any more. Ray

07-17-2010, 10:58 PM	#3
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,246	Re: dual master, rear end, and spring questions Ray is pretty much spot on. Although the GMC 4x4's did have the 12 bolts from 1963 to 1980 as well as the 8.5 10 bolts after about 1980-81. I would suggest trying to find one from a 1976 or newer since they had a little bigger brakes. If you plan on staying with 4 wheel drums, the '67-'70 master cylinder will work for you. If you convert to discs up front then a '71-'98 master cylinder will work....with a brake booster. The '71-'75's were available with manual brakes. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE Last edited by Captainfab; 07-17-2010 at 10:59 PM.

07-19-2010, 08:49 AM	#4
F-85 Registered User Join Date: Jul 2010 Location: Paw Paw,il Posts: 389	Re: dual master, rear end, and spring questions Im just gonna leave the drums. Ill get one of the 67-70 Masters. Has anyone used a Powertrax in one of these stock rears? Any other rear end options?

07-19-2010, 12:46 PM	#5
raycow Registered User Join Date: Mar 2003 Location: San Francisco, CA USA Posts: 2,454	Re: dual master, rear end, and spring questions For street driving I like the TrueTrac. It is smooth, noiseless, and doesn't require special lube. One to stay away from is the Gov-lock. Engagement can be violent and unpredictable. Ray Last edited by raycow; 07-19-2010 at 12:48 PM.



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