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all depends. once you exceed 6", you should seriously consider one. If nothing else it's a very good strength upgrade. But as long as you get a driveshaft of the proper length, you can get by without a SYE.

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set things to rest here...

 

 

an MJ has a longer wheel base than a cherokee. While most tech is the same between an xj/mj, rear driveshafts are NOT. you do not need a transfercase drop on an MJ until roughly 8" lift, if not more...given the correct rear driveshaft and proper (i.e. NO WEDGES) pinion angle is set.

 

 

SYE in a comanche is more a novelty than a necessity. Realistically, even 7" is too tall to be useful...

the only real benefit of SYE in an MJ is that you can break your rear driveshaft and still drive home. that said...you have to have a driveshaft made to work in the MJ, so if you're doing that you may as well drop another $100 to have them use the thickest wall they can...and you shouldn't ever dent it.

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the only real benefit of SYE in an MJ is that you can break your rear driveshaft and still drive home.

 

how? front wheel drive?

 

 

I think he means because all the fluid won't leak out of the transfer case when you remove the rear shaft with the SYE. And of course, it would be in 4WD

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the only real benefit of SYE in an MJ is that you can break your rear driveshaft and still drive home.

 

how? front wheel drive?

 

 

yep.

 

because the output is a sealed output.

 

you can also accomplish that by using a '96+ np231 or np242 and a normal (but correct length) rear driveshaft.

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did all the 242s have a sealed rear output?

 

96 and up. have one with a broken case sitting in the garage right now. two actually...one's a '91 nonsealed, and the other is a '99 that is sealed. luckily, the one with the broken case has 90k on it and just got dropped when trans service was being done (trans blew)

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I have never measured according to FSM, but I believe my rear has ~8" lift, possibly a bit more. Got a JY Toyota drive shaft (same u joints as stock Comanche, but it was longer) and had it cut down to the size i needed, then rebalanced with slip yoke and u joints installed. Between the 1" longer snout on my new rear axle, and 3/4" longer YJ slip yoke I still needed a 1" longer than stock drive shaft. Stock would have worked, but needed replaced anyway due to bent and dented. Incredible amount of droop, and no binding issues even at full droop. No vibes either due to correct angles.

 

Would like to get a SYE at some points in the future and a double cardan shaft (like the front one) so I can turn the pinion up and keep the DS out of harms way, as well as have FWD capability in case of drive shaft failure. Just don't know how I can keep the pinion bearings lubricated that way as the needed angle should put it above the axle tube.

 

Also been thinking about double cardan joint on both ends so I can set the pinion angle wherever I want.

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  • 4 years later...

Would like to get a SYE at some points in the future and a double cardan shaft (like the front one) so I can turn the pinion up and keep the DS out of harms way, as well as have FWD capability in case of drive shaft failure. Just don't know how I can keep the pinion bearings lubricated that way as the needed angle should put it above the axle tube.

Now THIS is a thought!  The only thing I don't like about my 8.25 is the front of the is SO low and bulky. 

Anyone done this?

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I have never measured according to FSM, but I believe my rear has ~8" lift, possibly a bit more. Got a JY Toyota drive shaft (same u joints as stock Comanche, but it was longer) and had it cut down to the size i needed, then rebalanced with slip yoke and u joints installed. Between the 1" longer snout on my new rear axle, and 3/4" longer YJ slip yoke I still needed a 1" longer than stock drive shaft. Stock would have worked, but needed replaced anyway due to bent and dented. Incredible amount of droop, and no binding issues even at full droop. No vibes either due to correct angles.

 

Would like to get a SYE at some points in the future and a double cardan shaft (like the front one) so I can turn the pinion up and keep the DS out of harms way, as well as have FWD capability in case of drive shaft failure. Just don't know how I can keep the pinion bearings lubricated that way as the needed angle should put it above the axle tube.

 

Also been thinking about double cardan joint on both ends so I can set the pinion angle wherever I want.

 

I talked to a friend of mine with 6.5" lift on an XJ and a SYE. He ran the truck on jackstands without an oil seal in the rear axle and it pumped gear oil out the pinion quite well. Evidently my worries about the pinion bearings were unfounded.

 

It is now almost 5 years later and the above mentioned driveshaft has been twisted in half during a stupid move (bouncing while doing a rear wheelstand) a few years ago. Had a bomb proof one made out of 3/16" wall tube. The sucker weighs about 50 pounds, but treated me well until I swapped 1 ton axles under the truck. Now with the 1 ton axles I did install a heavy duty slip yoke eliminator and had a stock front driveshaft retubed with 1/4" wall tubing, lengthened 19" and a 1310 to 1330BC in the bottom end of it to hook up to a Ford 10.25" axle.

 

On a side note, I built my daughter a Cherokee. Started with a rust free 1996 2wd model, and bought a rotted out 1996 4wd parts truck. Used the 4wd transmission, but not the transfer case. Instead I used a 242 transfer case out of a 1994 Grand Cherokee with a hack-n-tap slip yoke eliminator and 4.5" lift. She runs stock front driveshafts front and rear; kind of handy having to only carry one spare driveshaft.

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Hmmmmm, So If I lift my Comanche 4.5", I don't need an SYE? But I do need to get longer drive shafts front and rear??

 

Nope.

 

I put 5.5 on mine & never changed the drive shafts.

 

 

 

When I did SOA on my 89, I didn't change the shaft. Driving down the highway the first time at 60mph hit a gentle riser, rear lifted and the DS dropped out of the transfer case. Blew up my rear axle internals.

 

At that point I had a custom shaft built at a local shop that usually builds shafts for drag racers. Exact length based on my measurements, high angle yoke, massive tube, new u joints, fully balanced, and I was $125 out the door.

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