HP D44 Rear; anyone? Anyone? Bueler? Bueler?

Got a question for the all knowing-all seeing Forum members. Thinking about finding a HP D44 out of the front of some full-size FWD junker and putting it in the rear of the XJPOS of mine. I'm replacing the 35 rear and want to raise the pinion up and reduce the driveline angle. Since this will be reversing the rotation of the housing, will it need to be geared with standard rotation gears? Will it work?

Yes, it will work, no you don't use standard spiral gears. Only reverse spiral gears work in a reverse spiral case.

2 cautions: When travelling in a forward direction, you will be putting forces on the coast side of the gear, thereby decreasing the effective strength of the gear by about 15%-20%. Secondly, reverse spiral axles were never designed for constant duty. The oiling of these diffs is much less effective than a standard spiral housing.

Summation: Keep your pinion angle as shallow as possible to alleviate oiling problems, and keep your tire size at 33" or less. (That was a Currie recommendation from back in the days they were building RS44 rears.)

RS 44 rears have fallen out of favor due to the availability and vastly superior strength of the various RS 60 housings available in the aftermarket.

CRASH

Adding to what CRASH has said, by the time you retube the front D44 you're talking some custom work anyway. The Currie HP 9" becomes a better choice. You have your choice of larger axles, and the diff is designed to oil properly. I have friends who run rear HPD44's with 36" tires, and while they've broken axles they've never broken a ring and pinion. As far as oiling properly, these rigs are trail only so don't see steet time. I have broken a regular rear D44 ring and pinion with 33" tires........so anything is possible.

Save the somewhat hard to find front HP44 for a worthy project, and consider getting a HP 9" or spring for a custom rear HP60.

You can use a front in the rear? Hmmm don't know why but never really thought about this. Makes for some interesting thoughts down the road for a rear steer hi pinion setup. Do the front and rear d-shafts rotate opposite? My brain isn't working too well right now.

Goatman said:

Adding to what CRASH has said, by the time you retube the front D44 you're talking some custom work anyway. The Currie HP 9" becomes a better choice. You have your choice of larger axles, and the diff is designed to oil properly. I have friends who run rear HPD44's with 36" tires, and while they've broken axles they've never broken a ring and pinion. As far as oiling properly, these rigs are trail only so don't see steet time. I have broken a regular rear D44 ring and pinion with 33" tires........so anything is possible.

Save the somewhat hard to find front HP44 for a worthy project, and consider getting a HP 9" or spring for a custom rear HP60.

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I agree - for up to 36" tires (and maybe 37", depending on your style), the Currie HP 9" is a great choice and can be customized to your specs.

This setup is essentially a custom 9" housing built to your specs. It uses a Ford 8.8 gearset from the front end of a Ford Explorer in a custom third member (with proper oiling as Richard points out). You choose axles in 31 or 35 spline configuration (I run 31 spline because I think the R&P would break before the 35 spline shafts). Deepest gearset is 4.88.

This solution is stronger than a HP 44 would be, and also probably cheaper in the end. I run this axle and love it, although ultimately the savings aren't huge over the new breed of HP 60's out there (about $300 - $400 if I remember correctly).

The deal with going custom is, IMO, largely about spending all your money at one time or spending it piece by piece. A brand new custom heavy duty Currie housing runs around $300. From there you are adding axles, locker, R&P, and brakes, which is ultimately no different than if you get a junkyard axle, and labor is less if you do all of the install all at once vs. the typical piece by piece build of a junkyard axle.

The extra cost for the Currie axle comes in the form of the HP 3rd member. Get a quote for one of these axles and then figure out your costs for building a junkyard axle - unless you can do the diff work yourself, you may find the custom axle to be surprisingly cost competitive. Put that HP 44 up front.

Nay

Another stronger option I've heard of for a trail only HP 9" is flipping a standard 9" housing and retaining the pinion with 3 support bearings and the 9" ring gear. This would be for a trail only rig though as you run into oiling problems.

EDIT: I could be way off here but wouldn't it be better to flip a standard rotation front d44 for the rear because then the axle would be running backwards and the ring gear would be running on the drive side?

basalt51 said:

Another stronger option I've heard of for a trail only HP 9" is flipping a standard 9" housing and retaining the pinion with 3 support bearings and the 9" ring gear. This would be for a trail only rig though as you run into oiling problems.

EDIT: I could be way off here but wouldn't it be better to flip a standard rotation front d44 for the rear because then the axle would be running backwards and the ring gear would be running on the drive side?

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if you flip an axle over it will drive backwards, meaning 4 or 5 reverse gears and 1 forward gear, and even more importantly it will drive in the opposite direction of your other (unflipped) axle.

flipped 9s are done with 2 gear portal ends which provide gear reduction and reverse the rotation, thereby correcting it.

Even if it's a front you flip and put in the rear? So the front drive shaft and rear drive shaft spin the same direction (or different LOL)?

If you take a front axle, and put it in the rear, it will still drive in the correct direction.

There is no difference in design between a front and rear differential. The difference comes when the ring gear is oriented either to the right or to the left of the pinion. this determines which direction the axle spins.

CRASH

A friend of mine ran a HP44 for a month or so. IIRC, he broke ring gear teeth every time he took it out. After the 2nd or 3rd R&P job he upgraded to a HP60.
Paul

CRASH said:

Secondly, reverse spiral axles were never designed for constant duty. The oiling of these diffs is much less effective than a standard spiral housing.

Summation: Keep your pinion angle as shallow as possible to alleviate oiling problems, and keep your tire size at 33" or less. (That was a Currie recommendation from back in the days they were building RS44 rears.)

Click to expand...

Are you sure about the constant duty / oiling issues with the HP set up?

I only ask because it is kind of odd to have that combination available with the NV242 from the factory if that is the case. Or are these issues specific to the HP D44?

What would you say is a reasonable max angle for pointing the diff at the t-case?

I haven't had a D30 (LP or HP) apart yet so I am intrigued by this. I'm swapping to a HP30 in the front at the same time lifting ~4.5" so I'm hoping the front drive shaft and diff orientation angles don't change much.

Is there a slinger on the pinion? Maybe adding one if there isn't would be helpful?

r@m

I think currie used to recommend no more than 15 degrees of pinion angle.

Remember, we are talking about a rear axle, which sees power all the time.

All HP axles should have a slinger in them, they are all shipped from Dana and AAM that way.

CRASH

CRASH said:

I think currie used to recommend no more than 15 degrees of pinion angle.

Remember, we are talking about a rear axle, which sees power all the time.

All HP axles should have a slinger in them, they are all shipped from Dana and AAM that way.

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Yeah, I follow. I was just thinking about a HP in the front. My truck more or less stays in full-time mode in the winter...and is a daily driver so...if there was anything I could do to increase oiling I'd be interested to hear. The ARB is going in once it comes up from the States so if there are "cool tweaks" to be done this would be the time.

FWIW, all the Scout LP D44 fronts I've ever taken apart have had slingers as well. Not certain if that an IH unique thing or not.

Anyway, I'll stop hijacking this thread now. :cheers:

r@m