Double cardan dirveshafts worth it for what I'm doing?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Spook50

Spook50

Skål
Supporting Vendor
10 Year 15 Year 20 Year
Joined
Feb 16, 2005
Threads
807
Messages
7,653
Location
Spokane, WA
One of the larger points I'm keeping in mind while prepping for the H55 conversion on my 62 is the fact that the tcase will be moved 6" forward when this happens. I also have a slight lift due to the full length Add-A-Leafs I installed, so rather than just lengthening the rear 6" and shortening the front 6", I figured I would have the rear lengthened 7" and the front shortened 5". This compensates for the tcase moving forward, plus an extra inch of length to accommodate the bit of lift I have. I figure since I'll be having them worked I may as well get it spot on.

Now my question is, since I'll be having them worked, would it be worth the extra expense (or even a good idea) to have either the front or rear modified for a double cardan joint?
 
The DC drive shaft should be set up with the pinion flange pointed towards the output flange on the transfer case. On the normal drive shaft the flanges are supposed to parallel. When I put an H55 in my 40 I went to a DC shaft because it got a little short and I was going SOA in the rear anyways so rotating the axle was no big deal. Runs pretty smooth past 70 on the hi-way. If you weren't going to rotate the axles anyways it may not be worth it.
 
Good points. I kind of figured it wouldn't be necessary with what little lift I do have. Especially with the rear. The front was the one I was mainly considering, and it's once in a blue moon that I go above even 50MPH when I'm actually in 4WD.
 
If you are staying spring under, and it sounds like you are, just use your existing drive shafts. Double cardan shafts would be a waste.

Do not get them changed until your swap is done, then measure the flange to flange distance and let your drive shaft shop set the length.

Alternatively, you can just use 85-87 FJ60 shafts which will be a direct bolt in.
 
second that, don't do driveshafts until your swap is in place. you can then check your angles and adjust or go dc. the rear angle is especially important, since you don't drive the freeway in 4wd. you might be able to get away with shims in the rear to get you back in phase.
 
Cruiserdrew said:
If you are staying spring under, and it sounds like you are, just use your existing drive shafts. Double cardan shafts would be a waste.

Do not get them changed until your swap is done, then measure the flange to flange distance and let your drive shaft shop set the length.

Alternatively, you can just use 85-87 FJ60 shafts which will be a direct bolt in.
Click to expand...

Yeah, the plan is to stay SUA. I think I'll take your advice and just measure the flange distance once all is said and done. There's a shop in town that I'm told has just a couple-day turnaround and does good work so I'll go through them.

I wonder how much lift a 60 or 62 can safely have before there's risk of the driveshaft separating under full spring extension.
 
1. The front & rear drive shafts actuality gets shorter at full droop. (this is if you have not done a shackle reversal)
2. The front & rear drive shafts get longer at full compression.
3. Things get weird when one wheel is at full droop and one is at full compression (twisted up in the rocks)

You can safely lift (SUA) a 60 about 4-5" without worry of the splines coming apart.

Dynosoar:zilla:
 
Dynosoar said:
1. The front & rear drive shafts actuality gets shorter at full droop. (this is if you have not done a shackle reversal)
2. The front & rear drive shafts get longer at full compression.
3. Things get weird when one wheel is at full droop and one is at full compression (twisted up in the rocks)

You can safely lift (SUA) a 60 about 4-5" without worry of the splines coming apart.

Dynosoar:zilla:
Click to expand...

Ha, you're right. I had forgotten how the front end behaves with the stock shackle configuration. But with the rear shackles on the far end of the springs (from the tcase), wouldn't the rear driveshaft still extend as the springs droop?
 
Spook50 said:
Yeah, the plan is to stay SUA. I think I'll take your advice and just measure the flange distance once all is said and done. There's a shop in town that I'm told has just a couple-day turnaround and does good work so I'll go through them.

I wonder how much lift a 60 or 62 can safely have before there's risk of the driveshaft separating under full spring extension.
Click to expand...

On my truck I have SUA, 4" OME/MAF lift. Witht eh sway bar out it flexes very well. The front prop shaft would seperate under flex.

I did a C&T on the front axle to fix this. I have DC shafts front and rear and it still would seperate.
 
Here is some food for thought, straight from one of the well respected names in Driveshafts, Tom Woods Driveshafts. It is from thier tech info page.

"Many people mistakenly believe that a double cardan or C.V. type drive shaft will allow for greater operating angles than a conventional 2 joint or single cardan drive shaft. This is not true. Some types of C.V.'s will actually incur a binding interference at less of an angle than a standard two joint drive line, again depending on the individual components used. Additionally the C.V. itself is longer than more conventional components and will create a greater operating angle on the driveline, especially on very short shafts.

The real benefit to a C. V. (double cardan) drive shaft is smoother operation at higher operating angles and longer life. The C.V. assembly works by intersecting the joint angles at the center pivot point and delivering a smooth rotational power flow or surface velocity through the drive line. Therefore, with this type of driveline it is important to roll the differential upward so that you have minimal joint operating angle at the differential end. As any substantial joint angle would cause the pinion to try to speed up & slow down two times per revolution. Causing what is known as a torsional vibration. (Torsional vibrations will also be created in a 2 joint driveline that has unequal angles at each of the "U" joints). Rolling the differential upward will lessen the total operating angle at each end of the driveshaft. Now at the transfer case end of the driveshaft you have two joints equally dividing the total angle . This will double the life of the joints at this end, additionally you will be back up to full rated life for the joint at the differential end. I also believe a C.V. is stronger than a conventional driveline when turning through the same angle. This would be the result of transmitting the torque in a plane more perpendicular to centerline of the driveshaft."

Really good explanation of CV joints in my mind. For more go to their site and no I don't work for them I just appreciate good know how and info.

Tony
 
You must log in or register to reply here.

Share this page

Back
Top Bottom