HP or LP

2001XJ · Oct 30, 2011

Hi guys, been doing some researching and need some advice. I have a 2001XJ and currently have a dana 30 LP in front and Chyr 8.25 in back with 4.56s and 33's. I want to upgrade to 35s and have read a dana 30 HP (if you aren't going to upgrade to a 44) is the way to go. However, after some research I saw this:

Non-disconnect RS: "This has to do with the inherent problem with the Dana 30 when used with big tires and low gearing, housing flex. When you apply torque to a pinion shaft, it tries to force the ring gear away from itself, and causing the pinion to ride up the gear teeth of the ring gear. This torque loading flexes the carrier and the housing unless both are stiff enough to resist it."

So keeping that in mind, is the low pinion the better option, even though when you have taller lifts it becomes a PITA due to driveshaft angles?

Basically, I have the chance to grab a HP dana 30 from a 95XJ for $100. Should I grab it? Will this work in my 2001XJ (which I plan to eventually gear to 4.88s)? Is there a certain year I should look for keeping in mind I want to stay with the dana 30 since I do some good wheeling but not super aggressive/rock crawling/mudding

TIA

VAhasnoWAVES · Oct 30, 2011

the addition of things such as a truss, stout diff cover, and full case locker help prevent the ring gear deflection you described.

the HP (reverse cut) gears are said to be stronger than the LP (standard cut) gears, as the LP gears run on the coast side on the gears when moving forward.

VAhasnoWAVES · Oct 30, 2011

double post.

Wil Badger · Oct 30, 2011

That is not a problem that is only inherent in the Dana 30. Every single axle out there will try to do the same thing. There are axles how ever that are better at fighting the forces. There are axles like the 14 bolt and 9" that have a pinion support bearing at the end of the shaft that help in eliminating pinion flex or deflection.

number 3 would be the pinion support bearing on a 14 bolt

you'll notice on the end of a 14 bolt pinion a nub this is what rides in the bearing

131_9902_08_o+131_9902_dana_60_vs_gm_14_bolt+gm_14_bolt_pinion.jpg

A Ford 9" is the only other standard axle that has this type of support. You will not find anything like this on any regular front axle. Now when talking about strength and front axles you want to stick with HP for front axles simple because it allows you to run on the actual drive side of the ring gear when forward power is applied and not the coast side of the tooth of a ring gear.

You'll notice in this wear pattern the marks are on the sloped side of the ring gear this is known as the drive side, the strong side of the tooth.

You'll notice in this picture the wear pattern is on the back side or coast side of the ring gear, this is the weak side of the tooth

2001XJ · Oct 30, 2011

so, you guys are advocating the HP dana then obviously....is the HP dana 30 out of a 95' suitable for my 01'?

TIA

cherokeeforbyer · Oct 30, 2011

if your not wanting to spend a lot of money then i would just keep what you have untill you can get a 44 and then do the gears... I know that a lp and hp d30 will hold up just about the same with gears and tires. there isnt much difference except higher ground clearance with the hp

VAhasnoWAVES · Oct 30, 2011

the 95 should be fine. your shafts, knuckles, and unit bearings will all swap over. you will need to regear the HP30 to match, your LP gears will not work. the carrier should be the same though.

if your thinking of going bigger (said you wanted 35s), and arent having anymore problems with the LP axle other than worry, it might be a good time to start building a 44 for piece of mind.

if you want to make your LP axle last a little longer, just add a truss for now.

bobnoxious · Oct 31, 2011

Wil Badger said:
That is not a problem that is only inherent in the Dana 30. Every single axle out there will try to do the same thing. There are axles how ever that are better at fighting the forces. There are axles like the 14 bolt and 9" that have a pinion support bearing at the end of the shaft that help in eliminating pinion flex or deflection.

number 3 would be the pinion support bearing on a 14 bolt

you'll notice on the end of a 14 bolt pinion a nub this is what rides in the bearing

A Ford 9" is the only other standard axle that has this type of support. You will not find anything like this on any regular front axle. Now when talking about strength and front axles you want to stick with HP for front axles simple because it allows you to run on the actual drive side of the ring gear when forward power is applied and not the coast side of the tooth of a ring gear.

You'll notice in this wear pattern the marks are on the sloped side of the ring gear this is known as the drive side, the strong side of the tooth.

You'll notice in this picture the wear pattern is on the back side or coast side of the ring gear, this is the weak side of the tooth

Sorry, but that's wrong. Slope side is the weak (coast) side, and the straight (drive) side is the strong side. It's the slope that drives the ring gear away from the pinion. In the rear, the pinion is low and is driving on the straight side of the ring gear. When a LP is in front, it is now forced to "drive" on the sloped (weak) side. In order to make a front diff be droning on the strong side, the cut had to be changed, which meant moving the pinion up...no it's driving on the straight (strong) side.

Wil Badger · Oct 31, 2011

Whoops I did put that backwards didn't I...My mistake I'm not one for setting up gears. Though I do know the drive side is stronger then the coast side. I guess that would make sense that the straight side would be the stronger side of the tooth though. Sorry for the misinformation. We all make mistakes. The information is still correct other then have the pictures backward.

BoringDave · Oct 31, 2011

Somewhere I read that any front hp will be 30% stronger then it's lp counter part. And that a stock hp30 with 297x joints are just as strong as a lp44 with the same. Not sure where I found that though?

Dave

bobnoxious · Oct 31, 2011

Wil Badger said:
Whoops I did put that backwards didn't I...My mistake I'm not one for setting up gears. Though I do know the drive side is stronger then the coast side. I guess that would make sense that the straight side would be the stronger side of the tooth though. Sorry for the misinformation. We all make mistakes. The information is still correct other then have the pictures backward.

As long as we put out the right info, it's all good. I tried not to sound like a jerk :rtm:

bobnoxious · Oct 31, 2011

BoringDave said:
Somewhere I read that any front hp will be 30% stronger then it's lp counter part. And that a stock hp30 with 297x joints are just as strong as a lp44 with the same. Not sure where I found that though?

Dave

In general terms that's all correct...a HP D30 gearset as about as strong as a LP D44 gearset When going forward.

stroked88 · Oct 31, 2011

BoringDave said:
Somewhere I read that any front hp will be 30% stronger then it's lp counter part. And that a stock hp30 with 297x joints are just as strong as a lp44 with the same. Not sure where I found that though?

Dave

which is why the preferred 44 is one out of a late 70's ford truck since its HP

2001XJ · Nov 2, 2011

help me out....just making sure...another advantage of a HP30 is that the driveshaft doesn't spin when not engaged...is that correct? So its safe to say ALL HP30s are disconnects? or is that wrong? I have some vibe issues around 65-70mph in the front and when I removed the front driveshaft it drove smooth as glass. It would be nice if I upgraded to a HP30 and it took care of the vibe issue as well

lazyxj · Nov 2, 2011

2001XJ said:
help me out....just making sure...another advantage of a HP30 is that the driveshaft doesn't spin when not engaged...is that correct? So its safe to say ALL HP30s are disconnects? or is that wrong? I have some vibe issues around 65-70mph in the front and when I removed the front driveshaft it drove smooth as glass. It would be nice if I upgraded to a HP30 and it took care of the vibe issue as well

Later model HP-D30s do not have disconnects and do spin the drive shaft and axles all the time. Lock out hubs are the only way to keep them from spinning when in 2WD.

Have you tried to eliminate the vibrations?
My 2001 XJ (LP-D30) is at 4"s and had vibrations in the front. Using the adjustable control arms, I set the front pinion to less than 1 degree of misalignment, which gave only 3 degrees of caster.
A set of 2 degree offset ball joints brought the caster up to an acceptable 5 degrees. Everything is much better now.

I have seen cases front front vibrations/noises caused by a bad pinion bearing, so you might want to check that.

zachandandy · Nov 2, 2011

Yes the driveshaft will still spin, but the hp puts the drishaft at a much better angle.

Voteban · Nov 3, 2011

Just to toss some more HP advocacy in here, I smacked my front DS pretty hard a few times and then bent my LP a little more before I upgraded to a HP out of a 99 (into my 00). I like it a lot better, and it gives me a little more peace of mind knowing that I'm not going to destroy my front DS now. My drop brackets and arms hang a couple inches below my DS, where as they used to be at about the same level.

Does the 95 have the stronger U-Joints? I know my 99 HP does.

2001XJ · Nov 17, 2011

lazyxj said:
Later model HP-D30s do not have disconnects and do spin the drive shaft and axles all the time. Lock out hubs are the only way to keep them from spinning when in 2WD.

Have you tried to eliminate the vibrations?
My 2001 XJ (LP-D30) is at 4"s and had vibrations in the front. Using the adjustable control arms, I set the front pinion to less than 1 degree of misalignment, which gave only 3 degrees of caster.
A set of 2 degree offset ball joints brought the caster up to an acceptable 5 degrees. Everything is much better now.

I have seen cases front front vibrations/noises caused by a bad pinion bearing, so you might want to check that.

If I remember correctly my caster is at 6.5* and my lift is 6". Gears were brand new Yukons and the vibes only are at 70-75MPH which in a way is good I guess since it keeps me just below the speed limit...lol. The front driveshaft is new as well and all u-joints and even the t-case bearing is new.

motoxpete · Nov 18, 2011

For the price you can get a front rear for I would just throw a HP in. I'm in the same situation, I have a 2001 and I started installing my 5.5 IRO kit today. I already picked up a Dana 44 out of a XJ for the rear, and once I do the disk brakes I'll lock it and gear it. If I do end up gearing my Dana 30 and running it for a little while I'll deff just pick up a HP to drop in. Like someone else said, just the comfort of having a little extra clearance is nice. Still up in the air on the front rear though... just like many many other people lol. I'll be running 33's for a while at first and the 30 with a little bit of work will be fine there. However I do plan on going to 35's one day, so I'm thinking it might be a little pointless to throw money into a 30 if I'm going to want/need a 44 down the road. I know there are mixed opinions on this subject, however I really think I'm just going to put a Rubicon 44 in her

2001XJ · Nov 18, 2011

What do you mean by a front rear?

motoxpete said:
For the price you can get a front rear for I would just throw a HP in. I'm in the same situation, I have a 2001 and I started installing my 5.5 IRO kit today. I already picked up a Dana 44 out of a XJ for the rear, and once I do the disk brakes I'll lock it and gear it. If I do end up gearing my Dana 30 and running it for a little while I'll deff just pick up a HP to drop in. Like someone else said, just the comfort of having a little extra clearance is nice. Still up in the air on the front rear though... just like many many other people lol. I'll be running 33's for a while at first and the 30 with a little bit of work will be fine there. However I do plan on going to 35's one day, so I'm thinking it might be a little pointless to throw money into a 30 if I'm going to want/need a 44 down the road. I know there are mixed opinions on this subject, however I really think I'm just going to put a Rubicon 44 in her

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