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Move axle forward to solve driveline woes?

Jared

NAXJA Forum User
Location
Ogden, UT
Okay, so I have 6 or so inches of lift and a stock driveline. My XJ is a '91 so I have the old style output shaft. Needless to say, there are some vibes present with 4.10's, especially at freeway speeds. Since I have lifted the jeep, the slip yoke is slid waay out of the t'case. There is maybe 2.5-3 inches of polished surface sticking out of the case.

With far less spline engagement for the yoke, I have noticed alot more side to side play in it. I would bet that with about twice the length of slip yoke splines inside the case, my vibes would be substantially better.

So, the plan is to redrill my homemade spring perches to move the axle about 3/4" or so forward. I will have to drill the plate on top of the leaves to match also. This should move my slip yoke about 3/4" forward into the t'case, nearer its stock position. I don't want it completely back to its stock position, or I would risk ramming it into the transfer case with full spring compression. But with more of the spline length engaged, the play should be less and strength would be increased.

Hopefully this will not cause too much tire rubbing on the front edge of the fender opening.

Yes, I am aware of the longer yokes available. Yes, I am also aware that slip yoke eliminators are a much better solution. The neat thing about this idea is that it costs $0.00 and takes about 2 hours to do. I have NO CASH and I need the Jeep ready for Moab next Thursday.

What do you guys think?

Jared
 
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UH UH!:( :eek: You need SYE and new or rebuilt driveshaft. I wouldn't drive it to Circle K like that. JMHO Good Luck!
 
Seriously, why not? What will it hurt?

The springs are just as well attached to the axle as before, the shocks have plenty of clearance not to make improper contact with the axle, and any of the other stuff connected to the axle is made of rubber hose.

With the exceptions of a 3/4" shorter wheelbase and a tad less fender clearance of the front edge, what is wrong with it?
 
I think you and XJguy need to hang out together whenyou get there. Then you guys can fix each others junk. IMHO, drop the lift, drop the Tcase, at least get an extended SY.

This is the problem with your situation. There is no guarntee that you moving the spring mount on the axle is going to give you enough spline engagement. Pointing the pinion towards the Tcase may help, with shims or extended shackels.

You really have not given details of your lift in the rear. Blocks, shackels, AAL?

I don't have my SYE on yet, but I make sure I have enough spline engagement.
 
After tonight the rear lift will constist of the following:

- Stock XJ main leaf.

- Entire 1986 comanche leaf pack with ears cut off, mated to stock XJ main leaf.

- Homemade taller spring perches, incorporating about 1" of lift. They are 7" long to lower the chance of axlewrap.

- Stock shackles, which need to go soon.

- The pinion is pointed up about 4-6*, we did this when we welded on the perches.
 
BTW - This is most likely a very temporary fix. I just need to get the old thing ready for Moab before this Thursday.

I understand that this setup is not ideal. My question is this: Do you guys think it will help, and get me through the week?
 
Yeah, I actually have a 1" t'case drop. Should've said that up front. Thx for the advice Chuck. Hope all this crazy booty fabbin on my Jeep works. I hate to test stuff out 275 miles from home.

Hope somebody brings a welder!
 
DeadEyeJ said:
....- The pinion is pointed up about 4-6*, we did this when we welded on the perches.

You realize that when you move the axle forward you will be increasing the angles on your driveshaft right? (shortening the wheelbase will give you worse angles, just look at a TJ/YJ driveshaft) You may make the vibes worse by doing this and could cause binding if you have lots of droop.
 
Actually, I won't be. My driveline is staying the same length from joint to joint. That length is what determines your angles. The slip yoke is moving forward, yes, but this does not increase any angles.

If I had a SYE then my angles would get slightly worse. Then my driveline would get shorter from joint to joint. But without it, the angles won't change.
 
DeadEyeJ said:
Actually, I won't be. My driveline is staying the same length from joint to joint. That length is what determines your angles. The slip yoke is moving forward, yes, but this does not increase any angles.

If I had a SYE then my angles would get slightly worse. Then my driveline would get shorter from joint to joint. But without it, the angles won't change.

Are you f-cking high? Moving the output shaft closer to the rear axle will increase your angle, just like a short wheelbase Heep. Am I missing something? Consequently, that's why they recommend an SYE.......to reduce your angles. HELLO?
 
Am I missing something?

yes you are. He does not have a fixed yoke on the t-case end, and is moving the axle end of the ds in the same direction as the slip yoke works. The angles will may change ever so slightly at the joints, but not much.

Even if he is high, he can still do geometry.:rolleyes:
 
I agree, the driveshaft angles will be unaffected by this sort of modification.

The only problem I can forsee has to do with the amount you'll have to move the axle. Assuming the holes in your spring perches are 9/16" to fit the leaf pack centering pin. I'd say you would want a nice 1/8" MIN between your old hole and the new hole you would have to drill the new hole a minimum of 13/16" down the perch. Leave a little extra as your current holes might be egged out larger than 9/16" and you're looking at moving that axle more than 3/4". It would end up being closer to 1" which could cause some clearance issues with fenders and such when either drooped or stuffed. Actually, the hole in the u-bolt plate might be larger than the hole in the perch so you might even have to move the axle over 1" unless you make new u-bolt plates.

The other concern is if you move your axle forward 1" will the slip be too far into the t-case? If it is indeed sticking out as far as you say it is then 1" will probably be fine but it doesn't hurt to double check.

If this stuff checks out I don't see a problem running this as a temporary solution.
 
those stock rear shafts bind up EASY when your shit starts to flex with that much lift and no cv or sye.
 
Actually, the transfer case end of the driveshaft has bound up already, even before I have taken the rig seriously off road. It looks like I can use a grinder to clearance the yoke just a bit. A little bit goes a long way here, I would imagine.

It has only bound up when I have gone over railroad crossings too fast with no rear shocks hooked up (don't ask). But if it binds there, it will bind at Moab. Time to fire up the 'ol Makita 4".

This whole setup is a mess right now, but it'll be a cold day in Ecuador before it makes me miss Moab!
 
I have 6.5" of lif with mj leaves and shackles and a 4* shim and no t-case drop. My yoke is pretty much in as far as stock maybe a 1/2" farther back. Pull the shackles from an mj and get more height, better flex, and better pinion angles all in one. then stick a $7 set of shims from NAPA in and call it good.
 
I dont get it....How can you fix problems without $$$$$?

A real HILLBILLY
 
Well guys, I did it. I moved the axle forward about an inch.

It was a huge success, vibes are almost completely gone and the yoke is seated nicely forward. There seems to be enough spline engagement to be strong enough for hard wheeling. My only concern is that I may have moved it too far forward. I hope the driveline doesn't end up smashing into the transfercase any time soon! Hopefully the slightly stiff rear springs and brand new DT3000 shocks will keep the axle far enough from the body.

The comanche springs I put in at the same time are a good mod too. They seem to offer about 5" of lift when used with the XJ main leaf. I used the comanche main also and just cut off the ends. They flex ok and seem stiff enough for good towing. The ride is great too, just slightly stiffer than stock springs.

So far, I would recommend this fix (axle relocation) to anybody in a tight spot who needs a quick easy, temporary fix.

Just my 2 cents, Jared
 
Glad it's working so far for you. Since your axle is hinged at the front leaf spring perches, the axle moves backward away from the t-case on compression (stuff) and toward the t-case (and ultimate destruction of your output shaft) on droop.

Good luck.
 
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