losing 4x4

[giorno71]

hey guys, i have an issue with my 4x4, 94 yj 4.0 ho, i put it in 4 high and i get a clunk (while driving on or off road), lose 4x4 and then it kicks back in, only seems to clunk when i lose front wheel drive not when it kicks back in, some times it dose it right away other times it takes a few min to happen
dose not seem to do it in 4 low or i haven't waited long enough to experience it. had the t/c apart and everything looks fine, chain is not stretched, no missing teeth on gears, and the Teflon pads are all good, bearings seem good, checked my front d/s, diff, vacuum disconnect and axle spline collar and all that's good.

                                                                                                                                                                        any ideas would be helpfull, Thanks

[jpthing]

I would suspect the front axle disconnect...

[Vinman]

I'm don't know much about the vacuum disconnects but is it possible you have an inadequate vacuum supply to the axle?

[cLAY]

Bingo! You probably have a leak in the vacuum system somewhere and when you are low on vacuum, like when heavy on the throttle, the disco motor loses vacuum allowing the collar to slip back.

Check the lines, tcase switch, disco motor and vacuum reservoir for leaks.Or just shim the disco fork into the engaged position and never worry about it again.

[binare]

If that stupid discos your prob... do the tj axle swap and never deal with it again... bonus... seals are easier to replace and will last longer. If you dont have seal issues... do like Clay suggested.

[giorno71]

i suspected that first but all lines are good, if the shift collar was slipping off the intermediate axle the 4x4 light would also be going off and on but it never even flickers and also i rigged the airline switch to keep the front axle in 4x4 with the t\c in 2 high and no clunks or noises at all, just the hum of the front axle engaged, drove it like that for a day and a half and not a sound so i doubt its the vacuum disconnect

[binare]

Actually you can break that fork and your light will function as normal. it dont care if the fork moves... only that the diaphram did.

[giorno71]

nope, the fork is fine, i checked that too. pulled it out and put it in 4 wheel and could not move the fork at all, took it out of 4 and it moved back perfectly

[hps4evr]

years ago on my yj i had a similar problem and i found the fork cracked on the bottom side and i couldnt see it. when vacuum applied to it the shaft would slide over but the fork would bend at the crack. if you havent dis-assembled the fork housing completly might be worth the few minutes to do so.
on mine i replaced the4 fork and all was well. i heard there was at one point an upgraded fork made of iron.
before i stripped my yj apart i had a similar problem again except on the highway in 4 hi it would feel like it was kicking
in and out of 4wd but the light stayed on. i sold all the parts and never found the issue though.
either way, the one piece axle would be a great upgrade at this time. i know of 1 person on this board that has all the parts you need.
keep us posted on what you find.

[cLAY]

On my xj it was a combination of a small leak in the diaphragm of the shift motor and a cracked reservoir and a leak in the line going to the cruise control. It only kicked out when I was heavy on the throttle and the front axle was actually pulling.

Try this, connect the lines sp the shft motor stays in 2wd when the tcase is in 4wd. Don't just unplug the lines as the collar will  vibrate over while drivng and partially engage. Then drive with the tcase in 4wd. If the noise Persists it's in the tcase, if I doesn't then it's probably the shift motor slipping.

BTW even after fixing my problems the collar still slipped as the teeth inside were damaged.

[giorno71]

thanks, ill try that next and give the fork a good inspection as it only takes a min to pull it, ill keep u updated on/if i find the prob

[giorno71]

i think it is the shift fork causing the problem, i have a new question, can i take the 2 piece Axel shafts out of my 93 Cherokee, (no vacuum disco) and fit them in my 94 yj Dana 30 front Axel (vacuum disco)? and if so is there any mods i have to do to make em fit? they are both Dana 30 high pinion, reverse cut, 27 spline. the Cherokee is just a parts vehicle so i was thinking if that's possible ill do that insted of buying a posi lock, I'm cheep and i have the parts.

[vantagetes]

Yes but you'll need a block off plate and two axles seals.

This may be handy: http://www.stu-offroad.com/axle/yjd30convert/yjconvert-1.htm

[fug]

Or you could buy my one piece axle kit that includes spiffy new one piece axle shafts and the block off plates, seals etc.  My ad is in the for sale section  http://forum.calgaryjeep.com/index.php?topic=24565.0