Let's Here Those U-Joint Angles

[383gmc]

I know there's been endless discussion about driveline setup, but what I've found is mainly focused on pinion angle. I haven't seen too much discussion about u-joint angles. In the process of converting my '68 GMC SWB C10 from leaf to coil spring I've ran into a problem. I am targeting a 6" drop in the rear, but I'm having trouble with the u-joint angles. From everything I've found the max u-joint angle should be 4 deg. Anything beyond this will reduce life, and potentially cause vibration. The attached chart shows this relation. The attached diagrams show the estimated u-joint angles for a 1 and 2 piece drive shaft at normal ride height with a 6 inch drop for my truck.

One Piece Driveline:

As you can see the u-joint angles are 5.61 deg. This is with the pinion parallel to the transmission output shaft.

Two Piece Driveline:

The front joint is 0.89 deg, which is good. The rear joints are 8.6 deg. This is with the pinion parallel to the front driveline.


Again, all these angles are taken at normal ride height (curb weight). With the suspension at full bottom they will be worse.

My suspicion is that many people are running higher angles in their u-joints with good results. So I'd like to see what everyone is running. If you can, post the following information. I think this would be great information to compile. Thanks everyone.

Vehicle: 1968 C10 SWB
Rear Drop/Lift: 6" drop
Driveline Configuration: One Piece
U-Joint Angles: 5.61/5.61
Comments About Joint Life, Vibration, Performance, Etc: These are estimated values. I have no actual performance information.


Vehicle: 1968 C10 SWB
Rear Drop/Lift: 6" drop
Driveline Configuration: Two Piece
U-Joint Angles: 0.89/8.6/8.6
Comments: These are estimated values. I have no actual performance information.

[HO455]

There is a lot of information on this subject in the 4x4 section. They have the same problems, except they are going up. Imagine the angles on a truck with a 12" lift.

[Ruscal]

I have a 67 short c10 with a SBC 350 and t56 magnum trans. I set the front motor mounts as low as possible and have the harmonic balancer about 3/8" above the front x member. I set the trans x member to provide a 2.8 degree down tilt. I then set the rear end to match the 2.8 degrees.
You will want to attach your rear trailing arms 2 or 3" higher than the factory position at the front due to your drop. Then get your ride height as close as possible to what you want for stance at front and rear. If you are going to use spacer blocks between control arms and axle housing for drop you can taper them to fine tune your rear end angle. I did that and it worked great. Later I switched to a 9" rear end and just welded the perches at the correct angle so the blocks could be standard.
In your diagram it appears you have set the front of the engine too high or the trans x member too low. 5.8 degrees is not necessary nor desirable.
Russ

[383gmc]

Originally Posted by HO455

There is a lot of information on this subject in the 4x4 section. They have the same problems, except they are going up. Imagine the angles on a truck with a 12" lift.

HO455, thanks for the tip. I searched through that forum, but again most people are talking about pinion angle. I didn't see anyone stating u-joint angle. Also, when most people post they're talking about problems. I want to know the u-joint angles on setups that work.

[383gmc]

Originally Posted by Ruscal

I have a 67 short c10 with a SBC 350 and t56 magnum trans. I set the front motor mounts as low as possible and have the harmonic balancer about 3/8" above the front x member. I set the trans x member to provide a 2.8 degree down tilt. I then set the rear end to match the 2.8 degrees.
You will want to attach your rear trailing arms 2 or 3" higher than the factory position at the front due to your drop. Then get your ride height as close as possible to what you want for stance at front and rear. If you are going to use spacer blocks between control arms and axle housing for drop you can taper them to fine tune your rear end angle. I did that and it worked great. Later I switched to a 9" rear end and just welded the perches at the correct angle so the blocks could be standard.
In your diagram it appears you have set the front of the engine too high or the trans x member too low. 5.8 degrees is not necessary nor desirable.
Russ

Ruscal, what are your u-joint angles, or driveline angle and I'll calculate them? My engine/trans angle is 4 deg. The 5.6 deg is the u-joint angle. Sorry the diagram is a little difficult to read. My engine and trans are using the stock mounts, and I'd prefer not to change them.

[ck5566]

Subscribed, good to know

[Ruscal]

Originally Posted by 383gmc

Ruscal, what are your u-joint angles, or driveline angle and I'll calculate them? My engine/trans angle is 4 deg. The 5.6 deg is the u-joint angle. Sorry the diagram is a little difficult to read. My engine and trans are using the stock mounts, and I'd prefer not to change them.

Good question, I can't remember what it was. Trans was 2.8 down, pinion 2.8 up. The driveshaft length i'm guessing around 5' long, but I don't know it's angle. Lower joint angles are best. <3 degree works best. info can be obtained from Inland Empire Driveline website regarding workable angles etc. I'll check my angle and report back.
I purchase drive shafts from this vendor: https://www.iedls.com/#Power_Train
Check the "Education Zone" box and view "powertrain setup".
Russ
PS.
If you have sufficient space between the top of your trans, bellhousing and floor you could easily put a spacer block between your trans mount pad and x member which would lessen your engine angle and the Ujoint angle as well. a 1" spacer out of aluminum maybe with 1" longer bolts.

[special-K]

The reduction of life span isn't awful at 5-6 degrees. But to get angles ideal it takes rotating spring pads and you can raise the tail mount on the trans some*


* w/1pc shaft

[383gmc]

Originally Posted by special-K

The reduction of life span isn't awful at 5-6 degrees. But to get angles ideal it takes rotating spring pads and you can raise the tail mount on the trans some*


* w/1pc shaft

That would definitely help the joint angles. However, I'm already running into clearance issues between the driveline and the crossmember and cab. This is why I was also looking at two piece drivelines. I guess I could raise the trans and carrier bearing with the two piece driveline and see what that gets me.

[Ruscal]

I had to raise the hole through the rear x member and also trim it out to the passenger side some. I had a 4" diameter aluminum shaft to fit through.
After trimming the hole I took some light flat bar, fit and welded back around the hole similar to factory flange. It took an hour or so to do. I just rattle canned the fix.
Russ

[Cash3481]

I drilled out the rivets in the cross member where the trailing arms mount and flipped the mounts over to gain back pinion angle! That should gain you a few degrees as well!

[Ruscal]

Originally Posted by Cash3481

I drilled out the rivets in the cross member where the trailing arms mount and flipped the mounts over to gain back pinion angle! That should gain you a few degrees as well!

His truck is leaf sprung, so no mounts. If he chooses to use factory parts he should invert the mounts as you suggest to provide better alignment and anti squat.
Russ

[383gmc]

Originally Posted by Cash3481

I drilled out the rivets in the cross member where the trailing arms mount and flipped the mounts over to gain back pinion angle! That should gain you a few degrees as well!

I am converting from leaf to coil springs. So I can weld the trailing arm axle mounts on and get any pinion angle.

However, I'm not looking for solutions to change pinion angle. I'm looking for u-joint angles in functional vehicles. If some people could measure there setup and post it I would greatly appreciate it.

[Cash3481]

Originally Posted by Ruscal

His truck is leaf sprung, so no mounts. If he chooses to use factory parts he should invert the mounts as you suggest to provide better alignment and anti squat.
Russ

Originally Posted by 383gmc

I am converting from leaf to coil springs. So I can weld the trailing arm axle mounts on and get any pinion angle.

However, I'm not looking for solutions to change pinion angle. I'm looking for u-joint angles in functional vehicles. If some people could measure there setup and post it I would greatly appreciate it.

Sorry guys... I didn't read it slow enough! Ill continue to follow along for the education!

[Dunenutt]

I raised mine 4". Tried everything to get it to not shake. I rotated the diff, lowered the trans, spaced the carrier brg, and had two different shafts built ( one with a solid carrier brg. Nothing worked, until they built me this bad boy!

[HO455]

After looking about a bit the Spicer web site has this calculator and a bunch of info. In addition it will do two piece drive shaft calculations.

http://spicerparts.com/calculators/d...gle-calculator

Plus this one

http://www.4xshaft.com/driveline101.asp