Driveshaft angle?

Brian

Brian

YJ Enthusiast
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Nov 6, 2021
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146
Location
Hernando FL
Hope I am not bothering you guys, seems I always have questions. Before my question though....My intermitent engine miss has decided to disappear again. Driven over 60 miles today and had no problems.
Anyway. I have concerns about my driveshaft angle. With the frame level it is a 20 degree angle. Doesn't sound bad but looks so wrong to me. The skid plate is shimmed down equally 1and 1/2 inches. Jeep was raised by leaf springs before I got it (don't know how much). Could I angle the skid plate to decrese the angle?
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My 91 with a 2.5 RE lift has a bit greater DS angle than that by the looks of your pic and Ive never had any issues and Im sure thats the opinion you'll get from the majority of owners. Granted angle is a factor or use to the point the DS could be pulled from the T case from extreme axle drop and big lifts/flex. Thats where a SYE kit comes in. From the looks of your rig its pretty typical IMO. The biggest factor in DS angles, to a point mind you, is a difference of angles at either end. Most DS builders will recommend nothing more than a 1.5 degree difference between the two ends/U joint angles so things like axle or leaf spring shims are used to slightly rotate the diff. Its kinda had to tell on yours as the shaft is slightly rotated past the point of the yokes being flat or level buy to me it looks OK as far as overall angle.
 
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Gilaguy23 said:
My 91 with a 2.5 RE lift has a bit greater DS angle than that by the looks of your pic and Ive never had any issues and Im sure thats the opinion you'll get from the majority of owners. Granted angle is a factor or use to the point the DS could be pulled from the T case from extreme axle drop and big lifts/flex. Thats where a SYE kit comes in. From the looks of your rig its pretty typical IMO. The biggest factor in DS angles, to a point mind you, is a difference of angles at either end. Most DS builders will recommend nothing more than a 1.5 degree difference between the two ends/U joint angles so things like axle or leaf spring shims are used to slightly rotate the diff. Its kinda had to tell on yours as the shaft is slightly rotated past the point of the yokes being flat or level buy to me it looks OK as far as overall angle.
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Thx for the input. What started me thinking is I get driveline vibration during acceleration 1800rpm and up
 
Get an angle finder. It’s so much better to confirm what the angles are yourself than having people eyeball them. Your pinion angle looks too high.

Do the springs have shims on them? Take a picture. You probably got rough country 2.5” which comes with 6° shims (stupid).
 
machoheadgames said:
Get an angle finder. It’s so much better to confirm what the angles are yourself than having people eyeball them. Your pinion angle looks too high.

Do the springs have shims on them? Take a picture. You probably got rough country 2.5” which comes with 6° shims (stupid).
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I will take pics tomorrow and also do a better job of measuring angles. Visually looking at the springs, there is a shim between axle pad and spring. It is tapered about 1/4" to 3/16". On the right side the 1/4" is toward the rear of vehicle. Left side it has the 3/16" side toward the rear. That makes no sense to me. It would think both sides should have the thicker side toward the front to angle the diff up toward the trans. I will measure angles at the joints tomorrow.
Thanks to all for input.
 
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I might be misunderstanding your post, but yes, the axle needs to be rotated up in the front where the D shaft is attached as you indicate. A closer pic of a spring pad would be good but it sounds like they may be in backwards. Also most of the shims are aluminum and can crack or fall apart if the U bolts were not tightened or just from use and flexing. I cant see any logic to have 2 different size shims but who knows what others may have done. Something else I see is what looks like some pretty skinny, er...crappy lookin T case spacers. Looks like a section of pipe maybe?? You also mentioned 1.5" of drop. That's plenty and most kits are for 1" of drop with either much larger OD spacers or 1"x 1.5" or so metal stock. I see the likes of Vendor X selling the metal ones for $160 which is insane when its $20 worth of metal that can be had at home depot, Ace or any metal supply yard. BTW, im gonna say you have a 2.5" lift kit in there based off the picture.
 
OK, now I have some pic's to show. I was going to turn the one shim around so the thicker side was front, but snapped a U-bolt. Have to wait till I have new ones on hand.
I just don't like an angle of 20 degrees. I am going to angle my trans down some to shed a few degrees, unless someone says "don't do it". That is my 2nd tail shaft seal DRIPPING.

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The angle of the driveshaft doesn’t do any good without it being relative to the axle….put the angle finder on the axle and the transfer case output so we can see what those are. You can determine the axle angle by going around to the diff cover side and putting your angle finder on the cast circles to the right of left of the diff cover.

The transfer case is what it is based on the transfer case spacers and the axle needs to be roughly 2° below that to account for axle wrap. Nothing else matters unless the angles are so steep that they surpass the allowable operating angle of the u-joints.

To me your pinion looks too high but we’ll see. For what it’s worth, the “20° angle” doesn’t really mean anything. The axle and transfer case are not perfectly horizontal so 20° isn’t a true measurement of anything. That’s just relative to the ground which doesn’t matter.
 
OKAY Lets try this.... 1st 2 pic's are diff Right and left. 3rd is Transfer Case. Difference between left and right maybe because of the backward shim. Only a few degrees difference between Tranfer Case and Axle?

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Transfer case should not be at a lower angle than the axle. Though it would be better to see where you’re measuring the angle with a more zoomed out pic. Depending on how you have the angle finder set can alter the reading. Would be good to see the whole tool and what part it’s up against.

As for the different shims, unless the axle perches are welded all messed up, then the shims won’t really do much to the axle, but would tweak the springs when the u-bolts are tightened.

Typically for your lift the recipe for success is a 1.5” Bar transfer case drop, 2° shims, and call it good. The tcase lessens the angle by 2° so you raise the axle the same amount to make up for it, and the u-joints last longer from less stress than a fully stock driveshaft setup with lift added.
 
machoheadgames said:
Transfer case should not be at a lower angle than the axle. Though it would be better to see where you’re measuring the angle with a more zoomed out pic. Depending on how you have the angle finder set can alter the reading. Would be good to see the whole tool and what part it’s up against.

As for the different shims, unless the axle perches are welded all messed up, then the shims won’t really do much to the axle, but would tweak the springs when the u-bolts are tightened.

Typically for your lift the recipe for success is a 1.5” Bar transfer case drop, 2° shims, and call it good.
Click to expand...
 
Your shims should be the same L&R.
What size lift does your Jeep have?
Did you install the shims or a PO?
Do you know what angle the shims are?
 
Stoopid Jeep said:
Your shims should be the same L&R.
What size lift does your Jeep have?
Did you install the shims or a PO?
Do you know what angle the shims are?
Click to expand...
The shim on the Right is installed backwards. Snapped a U-bolt when I went to fix, so now I will have to wait till I get new ubolts. I was told by others it looks like a 2.5 inch lift. I did not install so I don't have much info. Just learning for you guys as I go along
 
if your having vibration problems (generally over 45mph) you will need to replace the DS with a CV unit which will also require a Slip Yoke Eliminator kit for the T-Case.
This is a very common problem with spring lifts on YJs', body lifts not so much.
But your DS angle is very close to what mine was at 19 degrees after a 2-1/2" RC lift.
SYEs' are not that expensive but install does require removal of the T-Case.
As for the DS I recommend Tom Woods, usually cheaper than off the shelf stuff and guaranteed to fit.
Thank you AMC for turning Jeeps into cars....NOT!
 
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jeepjoe43 said:
if your having vibration problems (generally over 45mph) you will need to replace the DS with a CV unit which will also require a Slip Yoke Eliminator kit for the T-Case.
This is a very common problem with spring lifts on YJs', body lifts not so much.
But your DS angle is very close to what mine was at 19 degrees after a 2-1/2" RC lift.
SYEs' are not that expensive but install does require removal of the T-Case.
As for the DS I recommend Tom Woods, usually cheaper than off the shelf stuff and guaranteed to fit.
Thank you AMC for turning Jeeps into cars....NOT!
Click to expand...
Thanks for the info, will have to look into it
 
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