Hey guys, I'm a little new to the drivetrain forum but I have a big question I need answered. I'm guessing opinions will vary, but what I'm really looking for is people who have experience and can give an educated opinion! My question is about rear ends and here is my situation:

I am swapping about everything over from a 88 formula 350 into an 84 TA. The formula has a functioning posi 9-bolt disc rear with either a 2.77 or 3.27 ratio according to the tech data page (I haven't yet opened it to determine which it is and RPOs are nowhere to be found). The 84 TA has a 10 bolt 26 spline axles 3.73 ratio open disc rear (what a mouthfull!). I'll be running an L98 TPI that's had some upgrades including headers and exhaust. Future plans are to get it over 300 HP and to be safe I'll assume that it may some day attain 350 HP. Here are the options I'm consideringthe following:

1. just swap over the 9 bolt and either hold on to or sell the 10 bolt.

2. install a powertrax traction unit into the 10 bolt and sell the 9 bolt unit to cover or nearly cover the cost of the powertrax unit.

The only reason I'm considering the powertrax unit over the posi is to have the higher gear ratio. How would the strength of these 2 options compare considering the torque I'll likely be producing?

I won't be using the car in the winter or bad weather. It'll be a second car for summer only. How would the traction charateristics of each option compare? I want that nice seat of the pants feel and some solid quick acceleration without spinning the tires too much unless I'm in the mood for a burnout :-) Is there a significant handling difference between the limited slip and the powertrax unit? From reading other posts it sounds like corners can be tricky at times. Thanks for reading this marathon post and let's hear what the pros have to say!

 

Hmm, did I scare people off or ask a question that's already been asked? I know the 9 bolt is stronger, just want to see if the 3.73 geared 10 bolt with powertrax would be just as good or better for my expected power output.

 

Okay, I considered earlier, and now that have been tweaked, I'll venture an opinion.

10-bolt: New 28-spline axles, $300. Zexel take-off unit, $100 (or PowerTrax or most any posi carrier, $350-$400). Install kit, $100. Cast aluminum support cover, $150. Plus labor.

9-bolt: New 3.7x gears & install kit from www.9bolt.com , $475. Plus labor.

For about the same strength.

Note I didn't give you any credit for 26-spline axles.

IMHO, the only reasons to go with a PowerTrax are: 1) You can install it yourself if keeping the same gears with common hand tools and no gear set-up; 2) want the locker-like action for straight-line acceleration; or 3) you don't like the fact that posi manufacturers like Auburn & Eaton don't want you using synthetic gear lube with their product.

All from somewhat less than a pro...

 

I would stick with the 10 bolt and powertrax Heres's why; it is already in the car, it already has the good gears, and powertrax's are easy to install. I have a 10 bolt zexel with 3.42's and over 325 hp to the wheels and it is holding fine.

 

Thanks for the replies so far. After reading your responces I have a few more questions and clarifications. First, I'm not looking to spend a lot of money to upgrade these rears! The options are either add a power-trax unit to the 10 bolt as it is with the current 26 spline axles and 3.73 gears or swap in the 9-bolt as it is.

Do you need to buy an install kit for the powertrax unit? I saw it installed on horsepower tv or whatever show and it didn't appear to require one.

Are the 26-spline axles a huge detriment? GASGZLR, am I correct in assuming that yours are 28-spline?

That's all for now. please I need more opinions and advice here guys!

 

Yes mine are 28 since my car is a 90, but you could always go find some 28 spline axels out of a junk yard since the axels have to come out anyway to install the powertrax. If you mean a ring and pinion install kit, NO you don't need one for a power trax, that's the beauty of one, is not to mess with the gears.

 

I thought of that too, but realized that the carrier and axle shafts have to be compatible. Am I right about that?

 

With the PowerTrax, you don't need the install kit.

If you get a 28-spline PowerTrax, you can install it with 28-spline axles in what was a 26-spline-from-the-factory carrier. The PowerTrax eliminates the spider gears that make it 26- or 28-spline.

A clutch-type posi will be a little smoother on the street. But, the PowerTrax comes with stiff "strip/street" springs, and softer "street/strip" springs, so using the softer springs (which I didn't) would make it a little friendlier on the street.

The cast aluminum support cover would still be a good idea. And, aftermarket 28-spline axles are a significant step up from factory 28-spline axles.

PowerTrax, 28-spline axles, welded tubes would be much better than the 26-spline rear. Adding the cover would help, and aftermarket axles would complete it.