Shimmed my vacuum motor over, now it shakes

1985 XJ, dana 30/35, np231, 3 Inch lift.

Hey all, I got a little problem, and I'm lookin for some help.
I shimmed my vacuum motor over so the front axle's always engauged. I drove down the dirt road in 4hi and 4low, and got a clicking noise coming from the font end, and a little viberation. I shifted it to 2wd, and took off down my street. I hit about 30, and the whole jeep started to shake. It continues to shake while I'm slowing down untill I'm stopped.

Any clue what this could be? I'm leaning towards front drive shaft u joints, but I really don't know what it could be.

Anyone? I need this vehicle to commute, and I can't drive it Shaking like this.

I'm not sure what it could be, but rather than the shims, (I'm assuming you used washers?) Why not hook up with a cable actuated fork for the front end? (Dana 30 disconnect right?) I bought the full system, but a few guys have made their own, just search out front axle disconnect and you'll get a few different ideas.... Then you can lock the front axle when you want to, and have the option of 2 Hi as well....

Posi Lock, that's what it's called.....

http://rustysoffroad.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=rustys&Category_Code=4x4POSI

There's also the perm-a lock kit too, which may behave better than spacers, you'll have to ask/search around

it's shaking cause of bad ujoints or ball joints

The washer shim technique is perfectly fine and is what I use.....there is no way the washers are causing the shake.

I would say its either your ds is unbalanced or bad ujoints,or possibly bad pinion angle.Look to see if your slip yoke is worn out.

edit: Dont you have a non cv type ds on that year xj(one that looks like a round can at the tcase output)
ifso these shafts tolerate very little lift untill they bind and "click" I had a 3" lift on my old 86 that had that style front ds and had to end up going with a double cardan front shaft.

I was out fiddling around with it, and decided to ditch the front DS. No more shakes. The U-joint came apart, and needle bearings went everywhere. It didnt look too bad, but I'm getting a new one tomorrow. Slip yoke is fine.

And yes, that is the shaft I have. By my understanding, Newer XJ's had double cardan's in front, right? If so, couldn't I find a newer XJ with a double cardan in the junk yard with a ax5/ax15 and an np231, put new U-joints in it, and stick it in my jeep? That would be the same setup, right?

And I have another question. When I went up and played in the snow last time, I would intermittently loose 4wd. I'd be going, and the clicking would stop and I would loose traction. Do you think this is a result of the driveshaft slipping because of it not being able to handle how much lift i had? Or will eliminating the vacuum disco fix that problem?

Probably a linkage problem with the 4wd lever.

I dont think the front driveshafts on disco models are factory balanced because they werent designed to spin all the time.

Ray H said:

I dont think the front driveshafts on disco models are factory balanced because they werent designed to spin all the time.

Click to expand...

actually they do spin all the time...the differential and LH axleshaft still spin.


as for the shaft, you can't use one from anything other than your tranny option (i.e. you have an ax5, so you need one from an ax5) because the other tranny's (ax15, ba10/5, aw4) have longer double cardigan shafts. if you use one of those you'll need it shortened and balanced.

and, my 86 comanche has a factory double cardigan.

But if the driveshaft spun all the time, wouldn't I be feeling it when im OUT of 4wd as well as when I'm in 4wd? I'm only feeling it when I move the shift collar over ( wich is all the time now cause I shimmed it) and I'm in 2wd.

How much would I have to get it shortened?

What engine/tranny does your comanche have? Couldn't I use one from one of those on the rare occurnace that I find one in a J-yard?

engine don't matter, tranny does. the 2.5 and 2.8 motors are positioned the same, so the tranny sits in the same spot.

mine was a 2.8, now a 3.8 camaro.

I'm not sure what the length on the front is...it's easily 5 or 6" shorter than a 4.0 shaft. I just grab the shafts off 2.5's or 2.8's at the junkyard, it's easier.

cost to shorten a ds is the same as having one lengthened I would think(about $80)but I think that style shaft isn't worth the trouble,get rid of it.Length doesn't matter on this style...it's the design that's the problem.

...like I said I had that style on my old 86 with a 3" lift and it didn't like it at all.I ended up buying a custom double cardan shaft from six states distributors....cost an arm and a leg but it worked perfectly.

The reason you can't use a double cardan shaft is it won't mate up to your t-case output(you will see that it is a flange type yoke).You could get a double cardan yoke and bolt it in your t-case allowing you to run the better shaft.
You have the np207 case right?The different yoke should bolt in.May or may not have to have the new shaft shortened.I would bolt on the double cardan yoke and measure the length from t-case yoke to axle yoke(center of ujoint to center of u-joint)to see if any stock shafts will bolt in.
or...........
You might try a t-case drop to lessen the angle on that goofy style shaft.Cheapest route.

The reason you would intermittenly lose 4wd was probably the vac disco loosing vac and causing the disco to disengage....you shouldn't have that problem now that the disco is shimmed.(unless it's a linkage problem do a search on how to adjust your linkage on here)

HTHeace:

jeepcomj said:

actually they do spin all the time...the differential and LH axleshaft still spin.


.

Click to expand...

Hmmm, what do you suppose the purpose of the disco is?
I'll help you, the purpose is to reduce the number of parts that spin.
With only the LH axleshaft turning, the spiders and side gears are allowed to spin without spinning the carrier.

outlander said:

cost to shorten a ds is the same as having one lengthened I would think(about $80)but I think that style shaft isn't worth the trouble,get rid of it.Length doesn't matter on this style...it's the design that's the problem.

...like I said I had that style on my old 86 with a 3" lift and it didn't like it at all.I ended up buying a custom double cardan shaft from six states distributors....cost an arm and a leg but it worked perfectly.

The reason you can't use a double cardan shaft is it won't mate up to your t-case output(you will see that it is a flange type yoke).You could get a double cardan yoke and bolt it in your t-case allowing you to run the better shaft.
You have the np207 case right?The different yoke should bolt in.May or may not have to have the new shaft shortened.I would bolt on the double cardan yoke and measure the length from t-case yoke to axle yoke(center of ujoint to center of u-joint)to see if any stock shafts will bolt in.
or...........
You might try a t-case drop to lessen the angle on that goofy style shaft.Cheapest route.

The reason you would intermittenly lose 4wd was probably the vac disco loosing vac and causing the disco to disengage....you shouldn't have that problem now that the disco is shimmed.(unless it's a linkage problem do a search on how to adjust your linkage on here)

HTHeace:

Click to expand...

*snort

hahaha

dude, the double cardigan from factory EASILY handles 4.5" of lift. the yoke is bolt-on, and a factory CV shaft isn't all that bad, with stock lift. you're right, it's terrible for any mild lift, but a factory double cardigan works just fine. I had a 89 MJ running stock front shaft at 6.5" lift and coulda gone higher

Ray H said:

Hmmm, what do you suppose the purpose of the disco is?
I'll help you, the purpose is to reduce the number of parts that spin.
With only the LH axleshaft turning, the spiders and side gears are allowed to spin without spinning the carrier.

Click to expand...

that's how they're supposed to work.

but it's not a foolproof design. my front shaft still turns with the disco disconnected, and I don't have a locker

jeepcomj said:

that's how they're supposed to work.

but it's not a foolproof design. my front shaft still turns with the disco disconnected, and I don't have a locker

Click to expand...

I'll conceed that at times it may spin but theres no mechanical connection making it do that. Friction between the gears and of the lubricant, especially when its cold (thick), is the only reason it would spin.

Heres an explanation of the CAD system.
http://www.4x4wire.com/dodge/tech/solid_axle_cad/
(the right wheel is free to turn independently of the left. While the spider gears spin, the ring gear, and thereby the front driveshaft, stay stationary -- allowing for a decreased amount of drag on the driveline.)

jeepcomj said:

*snort

hahaha

dude, the double cardigan from factory EASILY handles 4.5" of lift. the yoke is bolt-on, and a factory CV shaft isn't all that bad, with stock lift. you're right, it's terrible for any mild lift, but a factory double cardigan works just fine. I had a 89 MJ running stock front shaft at 6.5" lift and coulda gone higher

Click to expand...

You kinda lost me here...
We aren't talking about a double cardan shaft.He has a more of a cv style shaft that doesn't tolerate lifts at all.....

but yea I agree totally with what you said about a double cardan shaft.
and x2 on what ray H said above....