Topic: 4WD not engaging

[garydubf]

Yep!  Both jeep and Dodge did away with the axle disconnect in around 99/2000.  For good reasons!  With the transfercase in 2hi the axle will still spin the driveline!  But the nondisconnect side of the YJ does too!

[jfrabat]

There's no disconnect on a TJ.  Yes  the front shaft will rotate, but that's what they are built to do

Then that means less MPG and more vibration (YJs dont have the front shaft balanced)...  That's what worries me.

Felipe

[oldjeep]

There's no disconnect on a TJ.  Yes  the front shaft will rotate, but that's what they are built to do

Then that means less MPG and more vibration (YJs dont have the front shaft balanced)...  That's what worries me.

Felipe

Less MPG - I doubt it.   Balancing a driveshaft is about $40 if you are having vib problems.  Realistically with a lifted jeep and bigger than stock tires you can't feel anything from the driveshafts.  Both of mine are home shortened with no balancing and less than perfect runout.

[garydubf]

There's no disconnect on a TJ.  Yes  the front shaft will rotate, but that's what they are built to do

Then that means less MPG and more vibration (YJs dont have the front shaft balanced)...  That's what worries me.

Felipe

Should be no noticeable change in MPG.  Your front end already spins while driving! Only have one side disconnected!!  Shouldn't experience driveline vibes either unless yours is allready bent

[jfrabat]

And how do you connect the 4WD light to the dash if there is no servo motor to send the signal?

[oldjeep]

And how do you connect the 4WD light to the dash if there is no servo motor to send the signal?

Swap out the vac switch on the tcase for the electrical switch used on non-disconnect cherokees.  Wire into that.

[jfrabat]

OK, I think I will have to put this down in the list...  Probably after the rear axle is changed (to a D44 or Ford 8..  For now, I will try to fix the current system, as I cant afford to change the axle yet (neither one of them, actually).  I got my hands full with the alternator that I should be receiving on Friday!

Thanks to all for the advise, though!

[Rob the plumber]

There is also a specific seal need to use a TJ front axle shaft in a YJ. TJ's also use a double cardan front driveshaft, where YJ's use a standard U-joint shaft. There might be a reason for that.
The only thing spinning on a disconnected YJ is the axles (up to the disconnect) and the spider gears. The whole differential, ring and pinion, and drivehaft stay still. Enough parasitic loss to notice? Maybe not.

The good thing about a posi-lock is that you can be in 4-low in tight trails and unlock the front axle to make tight turns easier. (handy in quad trails when you end up in a tight, burmed circle)

[garydubf]

enlighten me on the specific seal!  I did this swap on a buddies YJ with no seal changes.  All we did is fab'd up a plate to cover the disconnect hole!  I'm not sure I agree with your opinion about only the spider gears turning either!  The non-disconnect axle will turn the ring and pinion until there is a differential in force, thus turning the drive line.  The disconnected axle acts as a "floater" per say! Therefor no pressure differential, carrier acts like a spool!  Thats the way I understand it!  As for double cardan vs. single U-joint , you're right but the reason is for serviceabilty not balance!


I could be wrong, I've been wrong before!

[oldjeep]

enlighten me on the specific seal!  I did this swap on a buddies YJ with no seal changes.  All we did is fab'd up a plate to cover the disconnect hole!  I'm not sure I agree with your opinion about only the spider gears turning either!  The non-disconnect axle will turn the ring and pinion until there is a differential in force, thus turning the drive line.  The disconnected axle acts as a "floater" per say! Therefor no pressure differential, carrier acts like a spool!  Thats the way I understand it!  As for double cardan vs. single U-joint , you're right but the reason is for serviceabilty not balance!


I could be wrong, I've been wrong before!

If you use the jeep in an off camber situation, all your gear oil runs out the passenger side if you don't have the seal.

[garydubf]

Right!  But that seal is all ready there!!

[jfrabat]

Well, finally got around to taking a look under the Jeep, and sure enough, the double vacuum connector to the servo motor was unplugged.  I think I will need to make an extension for the vacuum lines, as it seems this will continue to happen as a result of the lift when the suspension is extended...  Either that or go for a Posi-Lock, but the extension seems like a MUUUUCH cheaper alternative!

[Jeffy]

You can get a lot more slack if you reroute the lines.  Instead of having them go in front of the engine mount and down, pull the lines back through and have then come down before the engine mount.  I doubt you'll have any trouble with them pulling out unless they get hung up on something.

[jfrabat]

That's a good idea!  I did not think about that, but I will give it a shot...  This weekend I will instal a bored out 62mm 4.0L TB, a new 167A alternator, and probably will get to work on the lug nut that I rounded out, so I will get this done as well (seems it will be cheaper than extending the lines!).

[jfrabat]

Well, the final solution was even simpler than I thought; I just relocated the collar that held the vacuum lines and signal cables to a lower point on the frame, which leaves ample room for the suspension to extend without pulling on the lines.