how can it not affect the rear. with the front sitting lower, the transmission is sitting at a very slight angle with the rear being higher. which in turns puts a couple more degrees on the u-joint. if you raise the front, it will level out the transmission more, which will help a little.
What length is your rear driveshaft from the center of one u-joint to the center of the other?
How much shorter is the TC output shaft with the SYE kit?
try some pinion shims in the rear end , and drop the tcase 1/2 in with some washers or something if you dont wanna shell out cash right away, but if you have the cash its the best solution.
Okay, Ordered the Tom Woods CV and SYE. Again have a 3.5" RE with 31's. Are degree shims necessary in the rear? If so what size? All depends on the angle?
WHen you lift or lower the front it will have no effect on your rear driveline angles. The WHOLE jeep also moves with the front lift, thus your springs and axles etc all stay relative to each other.
I just did an SYE on my jeep and a friends jeep. We are both at 6" of lift and both were able to use a front DS from an Aw4 XJ in the rear. I had one from an AX-15 but it was a little short.
WHen you lift or lower the front it will have no effect on your rear driveline angles. The WHOLE jeep also moves with the front lift, thus your springs and axles etc all stay relative to each other.
I just did an SYE on my jeep and a friends jeep. We are both at 6" of lift and both were able to use a front DS from an Aw4 XJ in the rear. I had one from an AX-15 but it was a little short.
ok either i'm missing something, or you are. so let me ask it this way. you said: "when you lift or lower the front it will have no effect on your rear driveline angles".
so if i left the front stock, and raised the rear suspension 8", you telling me there won't be any affect on the rear driveline??? i'd like to see that???
so if i left the front stock, and raised the rear suspension 8", you telling me there won't be any affect on the rear driveline??? i'd like to see that???
If you lift the rear 8" and left the front stock height your rear driveshaft angles would be exactly the same as if you lifted the rear 8" and lifted the front 8".
As you lift the front the rear axle is moving the same degrees up as the transfercase, basically the same as if you pulled up on a curb with the front tires.
how can it not affect the rear. with the front sitting lower, the transmission is sitting at a very slight angle with the rear being higher. which in turns puts a couple more degrees on the u-joint. if you raise the front, it will level out the transmission more, which will help a little.
When you lift the front end, the transmission's position relative to the rear axle will not change. Only a TC drop will affect this.
Lifting the front WILL affect the front driveshaft angles because the front axle is now lower in relation to the transfer case.
When you lift one end of the vehicle, the axle at the other end of the vehicle basically becomes a pivot point.
Here's a quick way to prove this.
Attach a stiff wire (coat hanger?) to the rear axle so that it extends forward and parallel to the driveshaft.
Jack up the front of the Jeep and set it on jackstands, let the front axle back down off the jack.
Check and see that the wire is still parallel to the rear driveshaft. No rear driveline angle change from lifting the front end.
Dr. Dyno said:
What length is your rear driveshaft from the center of one u-joint to the center of the other?
How much shorter is the TC output shaft with the SYE kit?
If I remember correctly, the stock driveshaft was 29.75" universal to universal and I think the new DS/SYE setup is 34.5" yoke center to yoke center. I'll have to go out in the morning and crawl underneath to measure if you want a dead on number. I used a 6 degree shim kit to tip the rear yoke up and it points to the bottom of the TC yoke. Being slightly below the center of the TC yoke allows for a bit of spring wrap under acceleration.
My RE 3.5" lift kit has finally settled a bit and is sitting at 22" from the bottom of the flare to the axle center on both the front and rear. This is 5" lift rear and 4.5" lift front. It looks great and the ride is almost like stock, almost that is
Forgot I had this picture on my server... the top shaft is a stock NP231 shaft, the bottom one is an AA heavy duty shaft.
yeah aparently i am missing something, cuz i still don't get it. the transmission/transfer case is attached to the body. with a suspension lift, the body goes up. so if the rear raises higher than the front, then the transmission/transfercase stays in line with the body. so the back of the transmission would be pointing up just like the body. since the axle is still down, wouldn't that basicaly create a "triangle"???
from the rear axle UP towards the rear of the transfercase, and then the transfercase/transmission are pointing back DOWN towards the front.
the way you are explaining it, it almost sounds like the body gets lifted, but the tranny/t-case just magically hovers between the axles without getting raised. like i said, i must be missing something, cuz i don't see how it can not affect the angle.
okay first off lift the rear 8" will affect the driveline angles, since the whole BODY WILL MOVE. Anyone ever put a jack under the back end of their jeep and raise it up, anyone notice how the angle on the rear driveshaft increases? If you lift the front higher it will increase pinion angles. When you lift the front the rear axle (the pinion) will not raise up higher b/c the rear suspension has not been touched. And now I am confusing myself going on about this b/c I thought this would be common sense...
and to the OP or whoever keeps asking. You may need a CY shaft and SYE, why not take a look underneath your Jeep when it is flexing and when it is stock, and feel for vibes, that will tell ya.
yeah the way ICEDXJ said it. if you jack up the bumper (the rear sits higher than the front) it will affect the rear driveline angle.
which reminds me of a good example. if i jack up the back bumper of my cherokee more than 2 inches, my rear driveshaft WILL NOT turn anymore, because the u-joints bind up. so if you still try to tell me that it doesn't affect the driveline angle, then i call BS.
As you raise the front end, the body and driveline rotate up. BUT, the rear axle (pinion) also rotates up because your leaf springs are connected to the body. So, if you raise just the front, the rear axle is doing whatever the body and driveline do. Same with lowering the front, whatever the body does, the rear axle does, they stay in relation to each other.
If you lift just the rear, now the relation between the body and rear axle changes so the angles change.
that's what i was originally trying to say, and i was being told i was wrong. the person that started this thread was sitting higher in the back than in the front. which is why i said to level out the front and it would make the rear driveline angle a tiny little bit better.
that's what i was originally trying to say, and i was being told i was wrong. the person that started this thread was sitting higher in the back than in the front. which is why i said to level out the front and it would make the rear driveline angle a tiny little bit better.
If he raises the front, it doesnt change the relationship between the rear axle and the body because the rear springs are connected solidly to the body.
You are imagining it as if the rear axle was bolted to the ground. Its not its bolted to the Jeep and therefore changes angle with the rest of the Jeep.
If you put in any rear lift/front lift the driveshaft angles change.
If you put in a rear lift without putting in the front lift the front driveshaft angle does not change, and the rear angle is no worse than it would be if you lifted them both at the same time
The pinion angle is tied directly to the spring perch angles, which is the same as the leaf spring/shim angles, which follow the springs, which are attached to the body.
If you jack up the rear of your jeep from the bumper, your axle droops and increases the driveshaft angle.
If you take the front lift off of the same vehicle and don't touch the rear your driveshaft angle change is equal to the t-case output change, and therefore the relative driveline angles dont change BECAUSE the axle is no further from the body than it was originally AND the pinion rotates downward with the body.
you guys keep saying that the angles don't change. so why is it that if i jack up my bumper more than 2 inches, my rear driveshaft binds up if the angles supposedly don't change???
