Permi-Lock?

OK...son's XJ (88 XJ, 4.0L, NP 231, Disco Front Axle) has had trouble shifting into 4x4. Light on dash says it's engaged, but front wheels are NOT engaged. Suspected disco axle...and looked into a posi-lock. Found a permanent solution called a "permi-lock", but write up says it's not for daily drivers. Why is that? I have an '89 XJ with non-disco D30 in front. Is the issue the continued wear on the coupling collar? Why couldn't you just "force" the collar into the locked position on the axle and call it done?

Help is appreciated.

You can, it will just be locked like yours then, pull the handle and 4wd is engaged. All you need is a prybar and a BFH. Unbolt/break the cover off and use the prybar to force the lever over in the disconnect. Good luck.

It's common to do that, or pull the axle and seal out and replace them with a long side axle and carrier seal from a non disconnect housing, and put a blockoff plate where the disco motor used to be.

it will cost you m.p.g. and if you have a GKN CV joint(which you dont because you have an NP 231) it will put too much strain on the joint spinning 60mph all the time and it will tear it up. Its just going to cost you at the pump. I took my disco motor apart and used a 1/2 " piece of copper tubing as a spacer to put the fork in the 4WD position. I would spend the $160 and get the posi lock. or go here: http://home.earthlink.net/~stevenschreiber/cabledis.htm

The vacuum operated disconnect eventually loses air tightness and won't shift the fork. If oil is dripping out of the vac canister, it's gone. I perma locked mine a few years ago. Locked the shift fork into the engaged position with a hose clamp, flipped the cover upside down and bolted it on. Voila, no disco. Just pull the lever and go like a late model. I also ripped out all the vac lines. You can get an electric transfer case switch to activate the light, but I usually know I put it in 4WD.

I don't think it's necessary to beat the cover off with a hammer or prybar the shift forks, but duct tape will seal up the hole for awhile. There should be no difference in mileage than any non-disco axle, but it might make a little for you. Wear and tear the same - the later axles back drive the shaft, and nobody complains about that. I've had no problems - and I get 4WD when I need it.

The real issue is $160 for a cable - they sure look like the same ones I see for PTO's or motorboats, at $25 to $40 in the supply houses. I guess the fabrication of the rest of the widgets is the difference. Plenty of writeups around, even using bicycle brake cables.

I understand the mechanics...and feel I've got lots of information here. What I'm thinking (correct me if I'm wrong), is that the Perma-lock is designated as "off-road only" and "not for daily driver" is that the locking collar was never intended to be locked in place permanently...it will wear the gear splines, or something if engaged all the time. Does this make sense to anyone else?

no, the axle will be engaged, so the front driveline will be spinning all the time. But if the t-case is in 2wd, then the driveline will be free-spinning in the t-case. so, as long as you have an open front dif. the front wheels will be free to spin, and differentiate from each other. I HAVE noticed though, that at speeds above 60mph-ish the driving can get a little rough since the front driveline is now spinning all the time, and is not a balanced driveline.

shit i've had my XJ ('88 with disco D30) for 4 years...the vacuum shift fork has never worked....

its always locked...just make sure your front DS is in good shape.

xjfreak40 said:

no, the axle will be engaged, so the front driveline will be spinning all the time. But if the t-case is in 2wd, then the driveline will be free-spinning in the t-case. so, as long as you have an open front dif. the front wheels will be free to spin, and differentiate from each other. I HAVE noticed though, that at speeds above 60mph-ish the driving can get a little rough since the front driveline is now spinning all the time, and is not a balanced driveline.

Click to expand...

But how is it different than the newer non disco ones at that point?

I just picked up a 4.10 geared Dana 30 today, and it has the vaccum disco... my 94 XJ is a non-disco front axle. I bought this thing so I wouldnt have to yank everything inside the axle apart to re-gear, and I really dont want to pull the carrier, brakes etc...

Is the perma lok really gonna make it a rough ride above 60? My XJ isnt a daily but I do drive it long distances when I go on trips.

It isn't.

Just make sure your front shaft is balanced, and make sure the UJ straps are tight. I shimmed over the shift fork with some washers about 3 years ago, and have put almost 25K on it since then, without an issue.

Jeff

Jeff in VA said:

It isn't.

Just make sure your front shaft is balanced, and make sure the UJ straps are tight. I shimmed over the shift fork with some washers about 3 years ago, and have put almost 25K on it since then, without an issue.

Jeff

Click to expand...

Stupid question time

how do I ensure the front shaft is balanced? I'm guessing it has to be checked by a driveline shop? Its the factory shaft so I'm assuming its balanced

Not stupid, good question in fact. Older models that had the CAD didn't have shafts that were balanced, but newer ones and 242 models did. Look for balance weights tacked on to verify that yours is balanced. Since yours is a non-disco, it should be balanced.

Jeff

mine is an '88 model... when the joints got a little sloppy...you new it.
I had it rebuilt at a DS shop and it was better than new.

Sorry to bring up an old thread, but is the only reason this is not ideal for daily driving because of the unbalanced drive shaft? Or is there other reasons also?

Thanks
Adam