Hello all; I've searched all over the place...and keep finding conflicting information. I've looked at so many webpages I can't keep them all straight so I'll just dump it all in one spot and see what shakes out. I'm running a Ford 8" from a 1978 Granada. I haven't pulled it apart and counted teeth, but previous driving behaviour supports the previous owner's claim that it has 2:78's in it. I want to build this diff with an Eaton TrueTrac. Eaton's application do***ent (here)..pretty much says my rear end doesn't exist....but also that it only suits 3:25 and larger ratios. I've read in a couple places about keeping as low as 3:00 with some 't******* of the pinion'. I don't know if that's true, feasible, been done, smoke and mirrors......conventional sense dictates this would be a less than wise idea, but I'm open minded... Other resources don't make any reference to minimum ge****t...some forums (here somewhere I think) have others adamant that 8"parts are 8"parts are 8"parts...all interchangeable no worries. I'd like to keep my tall gears. I've done the math and could go up if I have to...just trying to get a feel for what people have actually done. Thanks!! Laters! -Mike
I haven't played with 8" rears in a long time, but my guess is that the problem with the lower number gear ratios is that the pinion gear is too large to clear the large housing of the TruTrac. I just offer this as an explanation for why you're getting conflicting info. 8" parts are indeed 8" parts, but the TruTrac is a relatively rare beast, that presents it's own issues.
Yep, I agree with Squirrel. The original Ford 8 inch carrier will work with all available gear ratios, so if Eaton are saying the True-trac will only work with 3.25 and up, it must be a clearance issue with the True-trac itself.
I HAVE a nice set of 4:57's in a 9 inch. At 4000 rpm and 50 mph, let me tell you WHY you don't see them that often.... Yes, ordered that way from Ford, DSO. Cosmo
What about jacking car up and turning the wheel to see how many revolutions the pinion actually does, save pulling the pumpkin out. You will the have a rough guide. I presume that it isn't an open rear end? I was of the view that 8" R&P sets are a little harder to find when compared to the more common 9".
Call them and ask. I have. They were very helpful with my off-road stuff. Eaton Southfield, MI, United States Tel: 1-248-226-6200
Depends on the transmission. I am about to put 5.13:1's in my Falcon. It is, of course, getting a 0.50:1 6th, too.
Lol. No doubt. I'm pretty good at filtering out the bad info, that's why I'm asking. Most of what I found comes from places that deserve at least a little benefit of doubt. I certainly don't have any trouble believing that the truetrack, out of the box, won't fit anything taller than the 3:25's as noted in Eaton's literature. I found one of the places claiming putting in a 3:00 - <here> Here's "Tom's differentials" where they say the pinion 'may' have to be trimmed.... I have no issue calling around to all these places...just wanted to bounce it off the community here and see what, if anything, anybody had actually done in real life...not just a catalog. Thanks for the input so far!! -Mike
It's for sure an 8"? That might be an option. I wanted to go truetrac as it has no clutches (nothing to wear out), but that would be a mighty close second!
Just an FYI. I have an 8" with 3.0 gears with a locker in my 49. So it is possible Posted using the Full Custom H.A.M.B. App!
If it's an 8in you've got a 2.80, a VERY common ge****t in that axle (as in most of the 289/302-slushbox compacts of the '60s-70s.) I'm trying to think of where the clearance issues might come in...I'm sure there's potential for it, the Truetrac gearcase is basically a cylinder, while the typical open or friction diffs are much smaller and conical. You could always go down to a 3.4o-3.55 and run a transmission with another gear in it... The Truetrac is a nice piece, and it has certain dynamic advantages over a friction diff, but in most street applications the factory Trac-Lok (if you can find one for an 8in, they're not common) will last just fine as long as you're not running a big 351+ motor and beating on it.
Ack! You blink and all of a sudden it's a 3 week old thread.... After much more painful googling and deliberation....I've decided I'll probably just upsize the gears...not sure what ratio I'll land on for sure...but now it becomes a complete drivetrain decision...cam/torque converter/rear end/tire size....gahhh.... Thanks for the input all!! -Mike
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