By MTB on Sunday, July 22, 2001 - 07:00 am: Edit

I am planning to upgrade suspension. I will be replacing my front shaft and would like to replace my rear shaft too(Roto). Now I can get one from GBR (where I plan to get my front) or I can get it from AB(u-jointed) for less $. does anyone know if there is a differance between the two. When I e-mailed GBR about relpacing my shafts I said I would like to replace my shafts with cv shaft. do they make a double cv shaft for the rear or am I just going to get a standard u jointed shaft for the rear from GBR. GBR's is $500 with flange. AB's is I think $329 (u-jointed)what should I do which one will be stonger.
Thanks for any help and info.

Michael B

By John on Sunday, July 22, 2001 - 02:12 pm: Edit

What lift height are you upgrading to, as that could be a factor...Normally a std. u-joint will work on the rear...depending upon your upcoming suspension components.

By MTB on Monday, July 23, 2001 - 02:11 am: Edit

John
2" RT's with RT frt arms RT's rear arms. keeping my BD XT's and planning to remove sways and retain springs.

Michael B

By MTB on Monday, July 23, 2001 - 02:25 am: Edit

John I sorry I ment double cardan in the front. could you tell me the differance between a cv & double cardan shafts and what would be best to go with at both ends.

Michael B

By John on Monday, July 23, 2001 - 03:31 am: Edit

. could you tell me the differance between a cv & double cardan shafts and what would be best to go with at both ends.

A cv drive shaft has a single knuckle u joint. A cardon shaft has a double knuckle u joint for more severe driveline angle. I would wait on both until you have installed your suspension. Your rear rotoflex is shakey no doubt and may need replacing. If you need to replace, a std. u joint drive on the rear is sufficient with a 2" lift. At 2" some trucks may need rear pinion angle correction, but wait and see. I doubt you will need to replace your front shaft. Wait until your truck lets you know otherwise. I would also check your front u joints for wear as you install your kit for no confusing vibs if you get them

By MTB on Monday, July 23, 2001 - 03:41 am: Edit

THanks John

By Kyle Van Tassel (Kyle) on Monday, July 23, 2001 - 05:03 am: Edit

Actually thats not correct. A CV jointed drive shaft as we know it it just that. It has a CV on one end close to whats in your wheel. It has three trunions with needle bearings and an outter race of sorts that fits over top of them and rides in the outter shell. I havnt seen them on many things but they are out there. The old Bronco IIs had them in the later years. It was a complete POS..

Kyle

By John Lee on Monday, July 23, 2001 - 05:16 am: Edit

Actually John, I have to disagree as well. What we commonly term a "CV" driveshaft is not a driveshaft with simple U-joints on both ends. Rather, the commonly described "CV" driveshaft is identical to the "double-carden" driveshaft. Here's a pic of one: http://www.4xshaft.com/images/cv_angle.gif

The reason most double-carden driveshafts are referred to as "constant velocity" driveshafts is because U-joints cause variations in speed as they are angled, and the double U-joints close to the transfer box output cancel each other out. That is the reason the double-carden driveshafts should have zero angle at the pinion side, because the introduction of angle at the pinion will introduce further variations in speed between the transfer box and the pinion.

By John on Monday, July 23, 2001 - 05:24 am: Edit

John,I stand double corrected....but MTB gets our drift. Thanks for the correction of terminology.

By Kyle Van Tassel (Kyle) on Monday, July 23, 2001 - 05:26 am: Edit

Actually Bill was saying something about needing 2 degrees at the pinion so the trunions dont get all screwed up (He used a nicer term). If its at Zero the needle bearins wont be forced to rotate and they will wear small grooves in the trunion.

Kyle

By John Lee on Monday, July 23, 2001 - 05:32 am: Edit

Kyle,

That's possible. I think the U-joint angles cancelling each other out in perfect harmony is nice in theory, but it doesn't always come out that way.

On Ho's Disco, he has the RoverTym offset radius arms, which points the pinion downward. Ho also has the double-carden front driveshaft. In theory, changing the pinion angle by fitting the offset radius arms should have caused vibration in the front, but it didn't, at least not aything that was noticeable.

By Kyle Van Tassel (Kyle) on Monday, July 23, 2001 - 05:35 am: Edit

U joints and driveline angles is a very strange art. There are so many variables that arent consistent between trucks that its really hard to make blanket statements or products to address issues. Making things adjustable is about as good as it gets so that you can adjust so that it gets it done for your specific need.

Kyle

By John on Monday, July 23, 2001 - 05:39 am: Edit

In my way of thinking, as I have Ho's set-up as well is we do need to turn the needles by that small angle of error as Bill says...with the larger angle error that Ho and I have, I would suspect we will shorten the lives of the brgs somewhat by the "out of tolerence error" because that ellitical thing is going on with each revolution. I have been using my shaft 2 yrs now with more error than Ho...so I am curious as to when bearing wear will show up.Nothing yet.

By Kyle Van Tassel (Kyle) on Monday, July 23, 2001 - 06:20 am: Edit

Well , when Bill made that statement about a 2 degree error I saw his point but still didnt see why you would want it. He is saying they want it out by just a little out so that the bearings will rotate. 2 degrees isnt much and I say that in normal every day driving the pinion angle changes enough so that this can happen plenty. if it was a rigid front end with a never changing pinion angle I think maybe he would be correct. I think that by being out you would see vibs before wear. its a double edged sword..

Kyle