Rear Frankenaxles too short? ('88 XT, mild lift)

[jbobspants]

This winter I found a JDM rear differential with 4.11 gearing and a SureTrac LSD like I've been looking for, and got it installed in the rear of my '88 XT trail runner. Obviously the new differential is the newer style with "innie" axle cups, as opposed to my original "outtie" stub axles. I found a pair of new style CV cups that fit into the diff, and rebuilt them with my 23 spline axles and original XT outer joints.

 

I'm pretty sure this is a well-known procedure for using modern differentials with ea82 suspension, but the issue I'm having is the new CV cups are roughly half an inch shorter than my old ones. Seems like the old ones had an extension where the roll pin went through, which is no longer necessary on the new style. Anyway, the new frankenaxles are just barely long enough (I can jack the car up so that one or both rear wheels is off the ground and neither joint binds up), but twice now I've been on the trail and bounced/twisted something to the point where the CV joint (the inner DOJ) has separated.

 

So my question is for those who are familiar with this mod, did you see similar issues? Is there a different axle option that would give me that 1/2" back?

 

Is cutting and sleeving the axles an option?

 

 

[idosubaru]

if that picture is the CV joint you used - it needs a circlip in that outer end groove to hold it into the diff. 

 

if the circlip is in place (even though it's not in the picture), buy two new ones from Subaru and see if that helps. 

[Numbchux]

Unless you can find some deeper cups or longer shafts....I think your only option is to lower the diff to ease angles.

[AdventureSubaru]

Usually there's a corresponding diff drop to go with a lift. If you have 2 inches of lift, you want to drop the diff 2 inches and you'll be golden.

[jbobspants]

Thanks for the replies.

 

As for the clips, they are inside the diff (both sides, I checked). I haven't had any issues with the cups popping out of the diff, it's the shafts trying to pull out of the cups. See attached for the first one I broke, I was in a bad spot and had to hammer down, by the time I got out, the balls had worn the whole outer ridge away (where the snap ring used to live). I found the snap ring deformed inside the boot. Thankfully I had a spare CV to swap in, but now I'm fresh out of spares.

 

As for lift, initially I just had the FWD rear struts and the diff in the factory location. This was fine with the original diff on the old tires, but when I swapped in the LSD, the new cups being shorter caused the first incident. Here's something else I noticed...the right side CV shaft (passenger side) seemed about 1/4" shorter than the left. It's not really the shaft being shorter (I checked with them both out), but either the diff isn't centered on the body, the bushings are really worn, or I have something bent/twisted. After the first incident, I elongated the holes in the mustache bar to shift the diff closer to the passenger side and even out the distance between the CVs, and that seemed to fix my issue for a while. However, I realized 235/75R15 tires, even with tons of massaging to the fender wells, just don't fit. I ordered the SJR 2" spacers and also made a drop plate for the diff to compensate. At that point the CV shafts were basically parallel to the ground with the car sitting flat, which seemed like the safest position for the CVs. First time I took it out like that, I think one of them popped out (I recognize that sound when the balls are skipping out of the grooves), but then popped back in after a minute. When I got out to look, the diff was noticeably twisted towards the passenger side, like the driver's side CV was wedged against it before it popped back into the grooves.

 

I need to pull the diff again to check if the mustache bar is bent now, but I'm concerned if my axles are stretched this close to the limit, I don't want one odd bounce to pop one out again. Like I mentioned above, the main issue started from the modern (shorter) CV cups frankenstein'ed onto my old axle shafts.

 

@Numbchux: is it really feasible to find longer cups or shafts? That was basically my first thought, but after a lot of reading in these here forums, I got the impression that they're all basically the same for this generation.

 

Edit: attached pic

Edited March 21, 2017 by jbobspants

[Numbchux]

You might try a pair of '85-'86 EA82 rear shafts, they use a DOJ on the outside as well, instead of a CV, which will telescope a bit.

 

 

I don't know of an interchangeable inner DOJ cup that is deeper, but it might exist...

 

 

You're not the first to discover the rear diff being slightly off center. I've even tried swapping shafts, and found one side to be much more difficult than the other. And when I had my Chuxwagon with the original AA lift cranked up almost 2" beyond it's intended height, I ALWAYS broke axles on the same side.

[jbobspants]

That's comforting to hear about the diff, I was worried I might have had something more messed up than I thought. For the record, it was the drivers side on mine that was really tight getting the shaft on and off, whereas the passenger side always had plenty of room. And it was the passenger side that got hyper-extended that first time, before I started changing things around.

 

Thanks for the tip about the '85-'86 rear shafts, I just did a quick search and it looks like they're available from AutoZone for $75 plus core (part #60-7034). The compressed length listed is 20 3/8" (vs 20 3/4" listed for that part in a '88), but with double DOJs they should extend more than enough to give some extra length. Very excited to check those out!

 

I'm sure it goes without saying, but presumably those will fit up to the new style inner CV cups like my old frankenaxles do?

 

Also, since they list the same spline count on both ends, are they reversible, or should I pay attention to which end goes where? I suppose I'll find out if one side is different when I open them up to splice 'em together.

 

 

[Numbchux]

They are reversible.

 

 

The splines on the shaft should be the same, but I'm really not sure. There's also a chance with a remanufactured axle that they've cut them down....

[jbobspants]

Cool. Well I went ahead and ordered a pair from AutoZone, we'll see what I end up with. Unfortunately older Subaru's don't seem to be that common around these parts, if I can't find parts at a local or online retailer, I'm typically stuck unless I can find a kind soul out west to go junkyard hunting for me.

 

Thanks for all the advice, I'll post back here when I have an update, in case anyone else is interested in what I find.

[jbobspants]

Well, the new axles actually showed up yesterday, surprising since I chose the free shipping option. The compressed length is as listed on their website (20 3/8"), but didn't get the fully extended length due to not having enough hands. The OD of the DOJ cups is the same as mine, so hopefully that means everything will go together nicely...I had run into an issue with one of the newer cups for my frankenaxles where the OD was about 4mm smaller than the others, so my internals wouldn't fit inside. I think the smaller one had 21 splines on the axle shaft, where mine were 23 splines. So far all the cups that are 75-76mm OD have had 23 spline axles inside them, and have worked fine.

 

With any luck, I'll have time to get the new axles spliced into my new style cups tonight, and get them stuffed back in the car in time for the weekend.

[idosubaru]

You don't need local junk yards:

www.car-parts.com

USMB

[Gloyale]

You could also use old "male stubs" from an EA diff and then stock EA axles.  You'd need to mill a grove in a set of old stubs to take a circle but the spline count and size should be the same.