12 bolt true trac - how strong for towing. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

nm78bronco · 05-07-2025, 12:06 AM

I have a 1976 GMC 1/2 ton 454/th400/2WD suburban that I want to rebuild the rear axle. I want to tow with it, up to 5000 lbs and want to know if a Detroit true-trac is as strong a differential as a factory open-diff for the 12 bolt factory rearend. I live in the Rocky Mountains out west, so long pulls up hills will happen sometimes. I would be using a 3.73 gear ratio with the true-trac.

Does anyone tow using a 12 bolt with a true-trac? If so, how much weight do you tow that you’re comfortable with?

Thanks

LS short box · 05-07-2025, 04:24 PM

Not even close to apples but I have used the Tru Trac on a number of LS projects. A couple that had close to 500 rwhp. Beat on the pretty hard. No failures.
I would suggest a new set of 30 spline Moser axles as long as you are in there.

Pontiac1976 · 05-10-2025, 01:00 PM

1500lbs trails surge brakes 4200lbs car factory open 308gear 12bolt was 454 1977 now 305 no problem 1989-2006 ever weekend. I have driven this one hill is a kill on both motor unless you're doing 80 over the speed limit by the time you get to the ark of the hill you will drop 80 they both drove the same on that hill no power, just burn lots of gas there your rpm goes way up and no mph gain. I heard Tru Trac there pretty good.

chris989 · 06-07-2025, 09:18 PM

Like LS shortblock said,,

I have a TT in a 12 bolt 67 camaro,, 406/ ~550hp 4 speed car..

I beat the life out of it and the TT has never failed. When i replace the eaton friction posi's in my burb I will go TT.

I am also putting TTs in my 78 dentside.. can't go wrong..

Chris

05-07-2025, 12:06 AM	#1
nm78bronco Registered User Join Date: Apr 2011 Location: San Tan Valley, Arizona Posts: 31	12 bolt true trac - how strong for towing. I have a 1976 GMC 1/2 ton 454/th400/2WD suburban that I want to rebuild the rear axle. I want to tow with it, up to 5000 lbs and want to know if a Detroit true-trac is as strong a differential as a factory open-diff for the 12 bolt factory rearend. I live in the Rocky Mountains out west, so long pulls up hills will happen sometimes. I would be using a 3.73 gear ratio with the true-trac. Does anyone tow using a 12 bolt with a true-trac? If so, how much weight do you tow that you’re comfortable with? Thanks

05-07-2025, 04:24 PM	#2
LS short box Registered User Join Date: Jun 2015 Location: Carlos MN Posts: 2,591	Re: 12 bolt true trac - how strong for towing. Not even close to apples but I have used the Tru Trac on a number of LS projects. A couple that had close to 500 rwhp. Beat on the pretty hard. No failures. I would suggest a new set of 30 spline Moser axles as long as you are in there.

05-10-2025, 01:00 PM	#3
Pontiac1976 Registered User Join Date: Oct 2015 Location: Ottawa, Ontario, Canada Posts: 803	Re: 12 bolt true trac - how strong for towing. 1500lbs trails surge brakes 4200lbs car factory open 308gear 12bolt was 454 1977 now 305 no problem 1989-2006 ever weekend. I have driven this one hill is a kill on both motor unless you're doing 80 over the speed limit by the time you get to the ark of the hill you will drop 80 they both drove the same on that hill no power, just burn lots of gas there your rpm goes way up and no mph gain. I heard Tru Trac there pretty good. __________________ 1977 REG cab Long Bed with a 1984 Front Clip, 82 305 .60 over 9.0.1 flat top pistons, 4bbl, TH350, w/84 SS-intake & cam , w/ 1977 big block rad, 1975 gear box, 1984 master w/ metric fittings top & SAE fitting @ portion block, 1975 3.42 gear open diff. Duel 77-87 Factory air cleaner, duel inlet from rad support . Down sized 9' to new 8' Steel flat bed Was a 77 454 w/308 gear. Taken out 550 lbs. up front with motor clip change.

06-07-2025, 09:18 PM	#4
chris989 Registered User Join Date: Dec 2011 Location: Boise, Idaho Posts: 724	Re: 12 bolt true trac - how strong for towing. Like LS shortblock said,, I have a TT in a 12 bolt 67 camaro,, 406/ ~550hp 4 speed car.. I beat the life out of it and the TT has never failed. When i replace the eaton friction posi's in my burb I will go TT. I am also putting TTs in my 78 dentside.. can't go wrong.. Chris



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