Drive Line Measurements Question

chudlet

chudlet

TJ Enthusiast
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Apr 18, 2022
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480
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N Idaho
Just double checking my sanity and measurements here. I just put in 4" RJ springs, the Ultra High UCF skid plate and JB Conversions SSSye. So effectively my drive lines are seeing ~ 7" of lift. I have not changed any pinion angles yet. I don't see that changing the DL length more than 1/2" or so.

I measured the front ujoints C-C at right at 40", tires sitting on the ground at ride height but before any settling.
I measured the rear ujoints C-C at right at 18.5", tires sitting on the ground at ride height but before any settling.

Do these measurements ring true for other folks that match my specs?

I took my front DL and an XJ DL to the shop to have them resized to 40" and 18.5" and the shop is telling me my OEM front DL in neutral position is sitting at 40.5". When I took it out, it did look like it would reconnect just fine, but I didn't remove the rubber dust boot and just figured it was at full extension. With this set up, do I NOT have to replace or resize the front DL? I am of course, going to re-measure tonight, but a sanity check here would be nice and much appreciated. Thanks.
 
chudlet said:
Just double checking my sanity and measurements here. I just put in 4" RJ springs, the Ultra High UCF skid plate and JB Conversions SSSye. So effectively my drive lines are seeing ~ 7" of lift. I have not changed any pinion angles yet. I don't see that changing the DL length more than 1/2" or so.

I measured the front ujoints C-C at right at 40", tires sitting on the ground at ride height but before any settling.
I measured the rear ujoints C-C at right at 18.5", tires sitting on the ground at ride height but before any settling.

Do these measurements ring true for other folks that match my specs?

I took my front DL and an XJ DL to the shop to have them resized to 40" and 18.5" and the shop is telling me my OEM front DL in neutral position is sitting at 40.5". When I took it out, it did look like it would reconnect just fine, but I didn't remove the rubber dust boot and just figured it was at full extension. With this set up, do I NOT have to replace or resize the front DL? I am of course, going to re-measure tonight, but a sanity check here would be nice and much appreciated. Thanks.
Click to expand...

Do you know the collapsed length on the front shaft? It is not too common to have to adjust the front other then tube diameter if it rubs on the skid.
 
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Shop guy said it had about 1-1.5" available for collapse. I just ran with the "assumption" that the front would have to be lengthened a bit. I guess I don't recall reading anywhere that they had to be adjusted because most of the conversations focus on the rear.
 
chudlet said:
Shop guy said it had about 1-1.5" available for collapse. I just ran with the "assumption" that the front would have to be lengthened a bit. I guess I don't recall reading anywhere that they had to be adjusted because most of the conversations focus on the rear.
Click to expand...

That is perfect then.
 
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I have the same mods on a 2002 automatic . I set my pinion angles before I ordered my new driveshafts . The front measured 39-7/8 . The rear measured 20-5/8 . I don’t know how much difference in measurements my automatic transmission would be compared to your manual .
 
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My measurements were for center of front ujoint to center of rear ujoint . These measurements are slightly longer than measuring yoke to yoke due to the angle created by the double cardan joint .
 
Thanks for the sanity check, guys. I remeasured this morning and I am still at 40" and 18.5 c-c on the ujoints. Everyone is going to be slightly different but as long as I am in the realistic ballpark, I should be good to go.
 
chudlet said:
When I took it out, it did look like it would reconnect just fine, but I didn't remove the rubber dust boot and just figured it was at full extension. With this set up, do I NOT have to replace or resize the front DL?
Click to expand...

Increasing the lift is not much different than when your axle droops offroad.
The control arms swing the axle in an arc, so the DS does not change length much.
Unless you lengthened the arms to realign the bump stops.
 
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Just be sure to check the measurements at full droop . That will be the shortest your driveline will see . You don’t want the driveshaft fully collapsed before full droop . It’s also a good idea to try and bolt the driveshaft up to the rear yoke at full droop to make sure you haven’t exceeded the maximum angle your driveshaft can handle .
 
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JDM said:
Just be sure to check the measurements at full droop . That will be the shortest your driveline will see . You don’t want the driveshaft fully collapsed before full droop . It’s also a good idea to try and bolt the driveshaft up to the rear yoke at full droop to make sure you haven’t exceeded the maximum angle your driveshaft can handle .
Click to expand...

hoping to do that this weekend.
 
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