Setting rear lift height

[Gunnibronco]

I need to order my driveshafts & then finalize my pinon angle.

With my seats, cage, top, bumper, spare tire, etc (not a full tank of gas) installed I'm sitting at about a 3" lift (9" from rear axle to frame).

With an extra 275-300# in the rear of the truck. I drop about .5" I figure the extra weight is close to what I'd be carrying in tools, supplies, camping gear, dogs, etc on a trail run. I'd like to end up around the same lift as when I started this debacle, 3.5".

Should I add a .5" lift block? or 1"? I'm thinking .5", I can probably get some .5" flat stock and make it myself & weld it to my spring perches before I set my pinion angle.

The standard go-to measurement for a 3.5" lift would be 9.5" frame to axle, but is that fully loaded or unloaded? I didn't measure where mine was at before I took everything apart. If someone can take a measurement of their 3.5" lift and let me know where it sits, I'd appreciate it.

[Jesus_man]

I need to order my driveshafts & then finalize my pinon angle.

You should probably do that in reverse order?

I'm at 10.25" empty (no seat, little fuel, etc.) But I do have that huge bumper with a spare on the back.

I just ordered a Tom Woods shaft. I have yet to install it, but I converted the tail Yoke on my Atlas to a flange style, which gained me 5* more of droop and just a tad more length. Anyway, seems like good build quality, as it should be for this price!

[Gunnibronco]

I played with things yesterday. It's very hard to set a pinion angle without a driveshaft. I ran a string between yokes & got it pretty close, but it doesn't take the double cardan joint into account. I set a pinion angle & measured @ 8", and also with a temp 1/2" spacer added under the leafsprings. With the spacer the pinon needed adjusted, but the driveshaft length barely changed. So I think I'm safe ordering driveshafts & then setting the pinion angle. I'm going to do a 1/2" lift block, hopefully I can find the right material in town. Otherwise I'll remove the spacers for transport to NV, and do the final set up there.

The flange was shorter than the yoke? Where did you get the flange? I was planning on ordering from Tom Woods, probably.

[Jesus_man]

Got my flange from Tom Woods (great price as well). I spoke with Tom and we figured out what the best solution for me was. My shaft was at 25.5" long.

There is a rule of thumb for calculating pinion angle and I don't think you have to account so much for the dbl cardan.

So you currently don't have wedges welded onto your tubes? There are shims out that that might both correct pinion angle and give you the 1/2" you need.

[Gunnibronco]

My pinion angle was so far off I decided to cut my perches off and order new ones. I wasn't finding any wedges I liked. I'll call Tom Woods and discuss options. Maybe changing to a flange is best. My rear shaft is measuring about 27.5" right now.

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[Gunnibronco]

I'm going to call Tom Woods tomorrow. I took a bunch of measurements today.

Driveshaft length at rest 27.75"
Extended, both rear tires off ground 28.5"
This surprised me, thought it would be longer, with the longer leaf springs & shackle reversal.

Not sure if I need the flange or if a double cardan is ok
At rest:
Yoke @ t-case 4*
Yoke @ axle 20*
Driveshaft angle (string between yokes) 21.5*

At full extension
Yoke @ t-case 2*
Yoke @ axle 16*
Driveshaft angle 26*

My front extended further (36" rest, 37" extended), but with the high pinion D44, it's pretty flat. Didn't take angle readings.

[Gunnibronco]

Got my flange from Tom Woods (great price as well). I spoke with Tom and we figured out what the best solution for me was. My shaft was at 25.5" long.

There is a rule of thumb for calculating pinion angle and I don't think you have to account so much for the dbl cardan.

So you currently don't have wedges welded onto your tubes? There are shims out that that might both correct pinion angle and give you the 1/2" you need.

Just curious what the flange cost?

Did you go with standard, long travel, or extended life splines?

Any other upgrades? Trail warranty?

[Jesus_man]

Flange was $85, but I think it was over $100 from advance. I did the X-spline and he installed the dust cap (XC), but also sent me the boot in case I wanted to swap it out later.


Wasn't offered a trail warranty nor did I know one existed.

[Jesus_man]

Oh and here's what I was trying to say about pinion angle:

[Gunnibronco]

Thanks for the info.

I was considering the xc & xb splines, but when I saw that the driveshaft was only .75" longer at full drop, wondered if they were necessary. I'll get their opinion tomorrow.

I've seen that pic & similar for pinion angle set up. I've come close running a string from yoke to yoke, but figured waiting on the actual driveshaft to measure would be better. It probably wouldn't make a real world difference, but since the perches aren't welded yet, there is no reason to move forward till the driveshaft is here.

I'm assuming your front driveshaft is a normal double cardan 1310. Was it special made? Longer splines? My old rear shaft almost fits, but is fully extended with the truck at ride height. Actually, it probably doesn't fit now that I bumped my front end up about 1.5" to match the rear with the .5" lift block. I think I'm going to take the overload spring from an Explorer spring pack, and cut it short to make my .5" lift block. I still have some spring pack bolts for add-a-leafs that came with my JD lift 20 years ago. LOL.

[Jesus_man]

The longer splines also wear much longer too he said... So if I tabulate all the money I've spent on driveshafts in the past 5 years of wheeling, I probably spent more than I did on this shaft. If it lasts a long time, maybe I've made a wise decision to go with a spendy Tom Woods!

I think my front is just a modified factory shaft.

I like the idea of adding a small piece of leaf spring to get your 1/2". That seems like a good and cheap option.

[Gunnibronco]

What part of your driveshafts were breaking?

Any problems with the front? I was planning to get a TW front, but maybe I'll just have one of my stock ones retubed when I get to NV.

[Jesus_man]

Mostly just wearing out. I have some bad vibes on my rear shaft from sitting so long, then we did Blanca and I don't think there was much grease in them. The rear one was squeaking badly at the top! I have broken a rear yoke on my Atlas, but I really can't say that I have actually broken either driveshaft. Seems lack of maintenance has been the killer.