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How much front driveshaft slip?

Mastiff

Mastiff

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I'm trying to get a new front shaft to account for my lift and extra travel from ORD springs. I'm trying to figure out how much slip I really need. I've been emailing Tom Wood and it sounds like 4.5" is what he can provide from a standard shaft. More than that and it gets fancy and expensive.

What I've measured is a 2.75" difference in length between static and full droop (front axle hanging). My initial estimate was 6-7" based on these guesses:

2.75" droop + 1" axle wrap + 2" uptravel + 1" slop/extra for articulation = 6.75"

Am I being too conservative? It doesn't seem like some soft springs should push me into needing an exotic driveshaft, but maybe they do. If so, I'm looking at a $500 shaft. :doah:
 
From some research I have done, while your truck is sitting at rest on the ground, your driveshaft slip yoke needs have about 1-1/2" max clearance before it bottoms out. This is for lifted trucks, which have more suspension flex than your average car (cars are about 3/4" clearance max). Anything a slip yoke does after that while wheeling is anybody's guess.
 
When I was measuring for my front shaft I was expecting big travel numbers since I'm running 52's. What I found was that even with the more flexy springs the total slip needed is not as big as some build threads would have you think. I only needed a total of about 6.5" of travel from compressed to droop.
 
I can't answer that because I never had a flexy suspension with a stock rotation t-case but my measurements are with 2" up rotation.
 
Have you looked into a front driveshaft spacer, which goes between your transfer case flange and the driveshaft? This is what I had to put in my truck after I lifted it. I also have an off-set u-joint on the diff yoke, which can operate at higher angles than a stock u-joint. Along with some clearancing on the cardan-joint and diff yoke.
 
A little Pythagoras should make it easy. C2=A2+B2 (don't know how to do superscript on here but that's a squared). Take your driveshaft output and measure the horizontal distance to your yoke at full squat, that's your A2. Your B2 would be the distance from the height of your driveshaft output to the height of your yoke. Plug in to the formula and you will have your driveshaft length as C2.

Do the same on full extension and compare the to C2 and you'll know how much slip you'll have.

https://www.mathsisfun.com/pythagoras.html flip their example upside down.
 
nvrenuf said:
When I was measuring for my front shaft I was expecting big travel numbers since I'm running 52's. What I found was that even with the more flexy springs the total slip needed is not as big as some build threads would have you think. I only needed a total of about 6.5" of travel from compressed to droop.
Click to expand...

So that's in the same ballpark as I'm thinking. Where did you get your shaft made? Like I said, anything over 4.5" is special, at least from Tom Woods.
 
I had some NOS Spicer pieces I had been sitting on for a few years (sorry). My parts have a longer than average slip but they are not the long, high dollar exotic stuff.
 
Do a flex test. Add 2.5 " to the extended measurement. That compensates for axle wrap and those weird situations where you flex more than you thought was possible.

On compression I prefer to have 3/4" of an inch at full compression. This can help if your leaf spring bends or center pin breaks.

When the driveshaft is fully extended 1" is the minimum overlap.

Don't skimp on the driveshaft. I did for years. I have been super happy with my long travel driveshaft
 
With my basic TC HD springs, the standard shaft was not long enough. (maybe 3-4" slip) Even after Moab and several trips with the truck, it just happen to be that perfect situation that pulled it out. While on the gas a little trying to climb up, passenger drooped, I slide backwards a tad, and the rocks grabbed my axle. Out came the slip. This is with a full clocked case, so the angle is steeper and pulls at the shaft more.

Now I run a 7" IIRC, which sets me up for the future as well.
PS: my shaft is from TW, but had the tube shortened and the 7" added locally. Wasn't more than a couple hundred probably. It's not exotic and the shop had it on hand.
 
I don't know if "exotic" is fair, but it's a $150-200 adder compared to a run of the mill slip. I guess I'll go for it.
 
I am in the same boat as you. Talked to both Tom Woods and Jesse yesterday. I am running into a couple issues. First my angles aren't good. I have about a 21 degree driveshaft before flex and with 52's up front I have already dealt with separating the old driveshaft.

Unfortunately I am looking at a 42 degree 1410 10 inch slip from HAD. Over $1k, but I can't seem to find an alternative that isn't compromising somewhere.
 
4wheelinfury said:
I am in the same boat as you. Talked to both Tom Woods and Jesse yesterday. I am running into a couple issues. First my angles aren't good. I have about a 21 degree driveshaft before flex and with 52's up front I have already dealt with separating the old driveshaft.

Unfortunately I am looking at a 42 degree 1410 10 inch slip from HAD. Over $1k, but I can't seem to find an alternative that isn't compromising somewhere.
Click to expand...

that sucks. is your t-case clocked flat?
 
no, I didn't want to clock the transfer case. Heard too many people having issues with leaking etc. Plus that would have made it even worse!
 
I clocked mine 3 years ago. Hasn't leaked a drop once I learned a mistake made on first install. Yes, it makes the angles much worse.

Consider running a large single joint, like a D60 yoke set up. I believe that has more working angle.

My 1350 CV is 99% maxed out with full droop + over droop. I don't see signs of rubbing but its very close. Having moved my axle 1.5" forward has helped with the angle. I might move it another inch. I looked at the 1410 BAMF joint also, but I don't think it will clear the 700r4 pan.
 
4wheelinfury said:
no, I didn't want to clock the transfer case. Heard too many people having issues with leaking etc. Plus that would have made it even worse!
Click to expand...

yeah that's why I was asking. Your drivetrain must be pretty short, another option is to play with your caster a little. I'm hoping that I can get away with a 1350 CV / long slip setup with the added length of the crawl box. Or I might be rotating the C's.
 
The issue for me is that rotating the C's doesn't get me any less angle at the TC. I am at 8 degrees up at the output of the TC. My shaft is 35.5 center to center. With a driveline angle of like 16. That makes the operating angle at the TC about 22 degrees. That is static. You add in droop and I will be at 30 real quick. 30 is basically bind for a 1350 so that is why the jump.
 
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