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Detroit True Trac Question

M

M4Madness

NAXJA Forum User
Location
Springville, Indiana
I'm getting ready to regear my D30 and 27-spline 8.25" from 3.55 to 4.56. It is a daily driver with 32's that sees highway use as well as snow/ice. Selectable lockers are a little more than I'd like to invest in a 14-year old vehicle that has yet to encounter serious wheeling and only leaves the road during deer season. Not to mention that an ARB air locker is the only selectable locker available for the 8.25".

I'm seriously considering Detroit True Tracs after reading a lot of search results here. They seem to be good in snow/ice, yet still afford decent offroad performance on average trails. My question is: If I choose to upgrade to 29-spline axles, is all I need a 29-spline True Trac and a pair of 29-spline axles?
 
Huh? I don't think that Truetrac diffs are available for an 8.25 axle (wouldn't mind being shown to be wrong, though.)

I have a Truetrac in my front D30, and an Auburn clutch LSD in the rear 8.25. Works nicely in the snow.
 
Didn't realize that Eaton was making those. You'll need 29 spline axles, there isn't a 27 spline version.
 
Are the axles the only thing I need to make the upgrade? If I hit the salvage yard, I want to make sure that I get everything that can't be re-used off my 27-spline axle assembly.
 
cannot help with the axle bit... but...
27 spline 8.25s have a 1.17 diameter axle shaft
29 spline 8.25s have a 1.21 diameter axle shaft
I don't know it that means you need look at axle bearings and seals or not?
From what I've read elswhere you simply pull the 27's and put the 29's in, and since you are buying a 29 spline full carrier... you'd be done.


I run truetrac's front and rear on my rig (over 2 years now) and have no regrets.
My rig is a daily driver, and sees over 2000 miles a month.
 
I had a 92 XJ with the 27 spline axles and decided to run a Detroit Locker. I ordered the 29 spline axles from Quadratech from a later model Cherokee, I think the year was 97 and up, and a master rebuild kit that included all the bearings and seals etc. The 29 spline axles fit perfect in the earlier 27 spline axles with no mods. The tru-trac will work great for you in the snow and ice. I ran one in my front Dana 30. The Detroit Locker, on the other hand, I was running will give you gray hairs pretty fast until you get the learning curve down for ice driving. Randy
 
desertrandy said:
I ordered the 29 spline axles from Quadratech from a later model Cherokee, I think the year was 97 and up...
Click to expand...

Quadratec lists 91-95 as being 27 spline and 96-01 as being 29 spline (http://www.quadratec.com/advisor/jeep_oem_replacement_parts/axle/axleXJChryslerR.php). I've always heard that the cut-off date was around 5/96 (mine is 3/96). It would be great if there was a way to tell without having to tear into it. I really don't have the opportunity to tear it down before I buy the new components. I'd hate to buy new 29-spline axles if I already have them...

Also, why are the 29-spline axles listed as being 3.5" shorter than the 27-spline versions (29.75" VS. 26.25")?
 
Last edited:
Well, some of the 96s had 27 spline and others had 29. So, if you need a model year, best to say 98+
Just pull the diff cover, and count your splines. You will probably want upgraded shafts anyways, so it couldnt hurt to buy new.
 
M4Madness said:
Why are the 29-spline axles on Quadratec's website listed as being 3.5" shorter than the 27-spline versions (29.75" VS. 26.25")?
Click to expand...

Typo. Left or right, 27 or 29 spline are all the same length.

If you've got the skills to regear, it's a trivial task to pull a shaft and see if you've got 27 or 29 splines. On the trail with a few "difficulties" it's about a 1 hour job.
 
I switched one 27 spline 8.25 to a 29 spline/true trac and all you will need are the shafts and the 29 spline TT. the bearings/seals are the same.

I have run a TT on my trail rig with 35's/alloys and no issues. Fact is I beat the hell out of it for 4 years and it never gave me a problem. I now have that same axle in my street XJ and its still going strong 5years later.
 
For anybody else out there who doesn't have the skill to regear, don't pull the carrier on an 8.25. The bearing caps hold eccentric adjusters, and those set the carrier preload/position. For a trail repair, sure, go ahead and do it, but plan on at least getting a pattern check ASAP on the gear teeth.
 
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