Cut and turn LP axle

[gorman]

I'm in the process of building a new front axle for my XJ using a locally produced Gearmax pumpkin with custom made axle tubes. The inner C's are those of the original D30 and it will get WJ knuckles. The Gearmax pumpkin is based on Dana axles as they are owned by Dana Spicer and it comes with a factory locker. It's slightly bigger and stronger than a D30, but I don't think is quite a D44 - somewhere inbetween.

The question I have is: the pumpkin of the diff I'm using is a low pinion one. As I'm in the process of setting up the correct pinion angle and caster settings for the diff - most references I can find refers to HP diffs. The reference I found for a setup similar to mine (6" lift) but with a HP diff is 10 degrees pinion angle. Is there anyone who has done a cut and turn excersize on a low pinion front axle (I'd assume people who might have done this did it to a LP D44) - if so, what pinion angle should typically be used with a LP and 6" lift? My existing propshaft angle on the OE LP D30 is 10 degrees, but the pinion angle is not correct - if I were to correct the pinion angle, the propshaft angle will be reduced, not? (my current lift is not 6" yet - more around 5-5.5")

 

[tbburg]

The pinion angle you want depends on a lot more factors then the lift. Low/high pinion doesn't matter.

Basically, you want the pinion aimed at the output yoke on the transfer case if you have a CV driveshaft,(most, if not all XJs have a CV front shaft from the factory) For a conventional driveshaft, the pinion needs to be parallel to the output shaft.

I've never turned an XJ/Tj/ZJ axle(all my experience is CJs), so I.m not sure how you will deal with the drivers side UCA mount on the axle(it's cast into the housing on the D-30) Either a custom bracket, or an adjustable UCA would be my first thought.

The way we did it on our CJs was to set the housing in place with all the brackets loose(BIG c-clamps help)and aim the pinion at the transfer case output, then measure and mark the position/angle of the "C"s. Probably not quite as simple with the 4-link brackets.

Curiosity: what kind of gears do the Gearmax axles use? I've never heard of them

 

[RCP Phx]

Why even waste your time on a LP D30,thats just stupid!
Basically your on your own to measure out the angles since this is a 1-of-a-kind axle!

 

[dave92cherokee]

Simply put you can't do it. The oiling passages for lp and hp are completely different and designed to keep the r&p oiled in the correct orientation. If you flip a lp and make it a hp then it won't oil properly and tear up your diff.

 

[WB9YZU]

Pinion to drive shaft angle should be zero with a double cardan shaft.

Period.

Works for all double cardan shafts, front or back, regardless of lift.

 

[gorman]

I'm not sure how you will deal with the drivers side UCA mount on the axle(it's cast into the housing on the D-30) Either a custom bracket, or an adjustable UCA would be my first thought.

Curiosity: what kind of gears do the Gearmax axles use? I've never heard of them

Wrt the UCA mount on the LH side, I'm either going to make a complete truss similar to what TNT does or alternatively just a smaller cross over bracket like Rubicon Express does.

The Gearmax diff are manufactured in South Africa for the local pick up range. There are various models of the Gearmax axles some with factory lockers and other normal open diffs. The locker models are as follows, model 77, model 82, model 84 and the model 89. The 77 is the smallest and I'd say it's about the size of a Dana 35. The 82 and 84 are bigger than the 77 and are the most popular ones and also taking the same ring and pinion gears (which are also locally manufactured). The difference between the two is that the 82 takes 27 spline side shafts while the 84 takes 28 spline shafts. I opted for the 82 so that the OE Jeep sideshafts will fit. The Model 89, the big daddy in the line is what I'm using as my rear axle replacement and it's basically a HD Dana 44 and it takes Dana 44HD ring and pinion gears as well. The diff casting has the same shape as the alu Dana 44 used in the Grand Cherokees, but it is a cast iron casting. Down side (but not for me) is that the lowest ratios for it is 4.56, but I don't intend going bigger that 33" tyres, so it should be fine. Here a writeup on the rear on our local forum: http://www.4x4community.com/forum/showthread.php?t=17553

Why even waste your time on a LP D30,thats just stupid!
Basically your on your own to measure out the angles since this is a 1-of-a-kind axle!

This isn't a LP D30 - it's a LP Gearmax Model 82, which is bigger and stonger with a factory locker. I know it's a one of a kind, but I thought the angles of my setup would be very similar to the angles of someone who fitted a LP D44, hence asking the questions.

Simply put you can't do it. The oiling passages for lp and hp are completely different and designed to keep the r&p oiled in the correct orientation. If you flip a lp and make it a hp then it won't oil properly and tear up your diff.

I wasn't going to flip it to make a HP out of it, it's just that most writeups of cut and turn excercises are for HP diffs, but mine is a LP, so the angles mentioned for the HP (e.g. 10 degrees pinion angle on a 6" lift) won't apply.

 

[Dave41079]

Simply put you can't do it. The oiling passages for lp and hp are completely different and designed to keep the r&p oiled in the correct orientation. If you flip a lp and make it a hp then it won't oil properly and tear up your diff.

When the OP said cut and turn, I'm pretty sure he was talking about the inner C's for getting the right pinion angle and caster. Not flipping the housing upside down to pretend it's a high pinion. I had to read it a couple times to understand what was going on.

How much is one of these front axles going to run you? Would it not be easier and cheaper to just do the modifications to your D30 since 33's are what you plan on running? Or even look around for a HP D30. Seems to me if you did that parts would be a little easier to come by than a one-off axle.

 

[dave92cherokee]

ok yah after I re-read it i realized what he's talking about. Most of the people who've posted about getting a hp would be the best way as it moves the pinion up away from the ground further to prevent any problems. If you don't have access to a hp then you'll have to go the slow way of doing it and get the axle at ride height with the lift cut the inner c's and then rotate it until it's about 2-3 degrees below the output shaft of the TC. You'll be hard pressed to find any info about cutting and turning a lp as most people trash those and throw in a hp for clearance. But when you do it definately post up the angles you used so other people out there with a lp that want to keep it can know what to follow.

 

[gorman]

How much is one of these front axles going to run you? Would it not be easier and cheaper to just do the modifications to your D30 since 33's are what you plan on running? Or even look around for a HP D30. Seems to me if you did that parts would be a little easier to come by than a one-off axle.

If only HP D30s were as plentiful and cheap at the Junkyards here in South Africa than it is in the States. I know of about three that's available at the local junkyard, but they are selling them for close to R8000 (thats about $1000!) each. The thing also with modifying a D30 is that the parts aren't available in any 4x4 store and to purchase a different ratio ring and pinion at the dealers will just plainly cost you and arm and a leg. I can import suitable ring in pinions for way cheaper than they sell at the dealer, but seeing that I basically got the Gearmax housing for free and that the internals for it is cheap as it is all made locally AND the fact that it comes with a factory locker, made up my mind.

Although this is a one-off axle in terms of the way it will look and work, the parts on it isn't. The centre portion of the axle is all local Gearmax stuff while the axle shafts are the original Jeep 27 spline ones that fit straight into the Gearmax carrier. The inner C's are off a D30 and the outer knuckles will be WJ knuckles with WJ brakes and disks. For all intends and purposes, it will be a nicely beefed up D30 axle with a little stronger Gearmax centre (with locker).

I'll see if I can take a pic of it tonight.

 

[Dave41079]

Ok, that makes a little more sense then.