Ultimate 12 Bolt Rear End 63-79
Racevette has built the Ultimate 12 bolt rear end. It is available in a Spool, or a limited slip differential the strongest is the Detroit Truetrac the Eaton posi-trac is a good choice and no weakling in its own right. It is available in the following ratios include 3:73, 3:90, 4:11, 4:56, 4:88 There are even higher ratios. We will install a Nitro gear first, a US Gear second, a Motive gear third, and a Richmond (3:90) last because no one else is making that ratio. We stand behind all of our selections. 3 year unlimited total replacement. We of course install a solid bearing spacer instead of a crush bearing. A billet ring gear bearing cap, Heavy duty side bearings, A modified new heavy duty rear cover machined to make room for the larger gear, high quality bearings and seals, and the dragvette 30 spline inner axels.
You get your choice of pinon yoke size the 1310, 1330, 1350. The stock size for a Corvette is the 1310 and the 1330. A 1350 forged is available. It is a tight fit but it can be installed, Sorry the no one sells or makes a 1330 forged unit. Also note changing the size of your pinion yoke will most likely require a drive shaft change.
Which is better, Detroit Truetrac or the Eaton posi-trac. You can read the information from the Eaton instruction book. I took pictures of their information about there LSD's. Drag the mouse cursor over the large picture it will enlarge the print. If you aren't wild about a spool, I suggest the Detroit Truetrack, for drag racing or a street/drag car.
Here is why I prefer the Detroit Truetrac differential. The Eaton differential has clutches and springs that wear. The stock Corvette suspension allows the inner axles to bang into the cross pin that is supported by the brittle cast iron housing. This will eventually crack the housing and destroy the rear end after enough wear has occurred, that is why the warrantee is limited to 2 years for Eaton posi-tracs. A fix for this problem is to install a Dragvette 6-Link. One function of the “Dragvette 6-link” is to support the trailing arm and prevent the suspension from abusing the differential.
The Truetrac uses horizontal helical gears and end plates to engage the forward motion, they are hardened and wear minimally. They are several inches long so a few thousandths of wear is not a problem. There isn’t a cross pin to transfer abuse to the differentials case. The case of the Truetrac is hardened steel. It is easily twice as strong. There isn’t any maintenance. Oil modifiers are not required.
There are 6 contact areas to transfer movement compared to 4 in the Eaton posi-trac. The Truetrac will transfer 30% to the slipping wheel and 70% to the wheel with the most traction, instead of 50/50 for the Eaton posi-trac. That means better control in out of shape driving. It is quiet and operates smoothly as does the Eaton. The disadvantage of the Truetrac, it is heavier than the Eaton posi-trac.