Reinventing the D44 (HP)

[Gunnibronco]

This topic has been batted around here before. I'm hanging around Jeep guys lately (don't judge me) and I've stumbled on a new wrinkle.

The idea is how to cram a bigger, stronger gear into a HPD44. Yes, I know I want a 609 with a True Hi9. But money, time, etc won't allow for that yet.

Jantz engineering offers a kit to put D50 gears into the HPD44 housing. Pro: bigger ring gear, almost 9". Con: same pinion diameter as the D44.

I was at our club meeting a couple weeks ago and someone offered a HPD44 4.88 ring and pinion for cheap. I will need to regear when I get back on the road and I jumped on the chance. When I went to pick it up, I quickly realized this was a JK Rubicon HPD44 gear. I haven't bought it yet, but I started an internet search for any magic to install the gears into my axle.

Enter Jantz engineering's new kit: K4. This kit is made to install a rear JK Rubicon D44 ring and pinion into a regular D44 housing. Actually this would probably work for you guys with stock LP front axles. Pros: 8.9" ring gear vs 8.5" stock, larger pinion diameter than stock. Con: none except work and cost of the kit.

I've been emailing with Carl Jantz about using this in my HP axle. I'm not 100% sure it will work yet. Unfortunately, the JK Rubicon HP ring is still 8.5", not 8.9". It does have the larger, stronger pinion than the old D44 pinion.

So my questions is:

What is the weak point of the HPD44 ring and pinon with 37's, low t-case gears, and chromoly axles? The pinion or the gear?

Is it worth making the upgrade to the larger D50 ring?

Is it worth making the upgrade to the larger JK Rubicon pinon?

If only the JK Rubicon front gear upgraded to the 8.9" ring, it would make the decision easy. You would end up with a D60 pinion and a larger ring gear than the D44.

Below gen 1 D44 vs rear JKD44 vs D60

129-1007-15+dana-44-dana-60+ring-and-pinions.jpg

[Digger]

Pinion deflection is generally the weak point with a R&P set. Thus why the JK rear uses a bigger pinion shaft.

The JK HD44 upgrade seems worthwhile, the HP44 upgrade with the smaller pinion shaft doesn't gain you anything worthwhile.

[Rox Crusher]

the HP44 upgrade with the smaller pinion shaft doesn't gain you anything worthwhile.

Howdy digger......can you clarify this for me, I thought the HP Dana 44 gears were somewhere around 25% stronger than the LP Dana 44 gears ?

Maybe the ring gear is stronger but the pinion isn't ?

[Gunnibronco]

Pinion deflection is generally the weak point with a R&P set. Thus why the JK rear uses a bigger pinion shaft.

The JK HD44 upgrade seems worthwhile, the HP44 upgrade with the smaller pinion shaft doesn't gain you anything worthwhile.

Thanks for the input. I've read several opinions that the D50 isn't an upgrade due to the D44/D50 pinon being the same size.

I still don't know if the JK HPD44 gear can be installed into the Gen 1 HPD44. After looking at the JK pinion, my uneducated gut-reaction is that it must be a big upgrade. Even with the same size ring gear.

I combed through 3 of Jantz's threads on Pirate4x4 yesterday and learned more about these upgrades. Carl Jantz pushed all the questions about the HP options to the D50 upgrade. He obviously thinks the larger ring gear is a worth while upgrade over the JK HP44 with the larger pinion/same ring gear. Maybe this is because he can't get one to fit, but can get the D50 to fit.

If I was still running a LP D44 I would 100% do the JK gears and his kit. The ring gear is larger, the pinion is larger, the tooth/gear engagement is much better, and fitting the JK gears is not much extra work. In one of the threads he mentions that the JK upgrade makes the LP as strong as a normal HP, possibly stronger, especially if a load bolt is added.

the HP44 upgrade with the smaller pinion shaft doesn't gain you anything worthwhile.

Howdy digger......can you clarify this for me, I thought the HP Dana 44 gears were somewhere around 25% stronger than the LP Dana 44 gears ?

Maybe the ring gear is stronger but the pinion isn't ?

I think this is considering running a LP in the front. This puts the pressure on the coast side of the gear which has less strength than the drive side of the gear. I don't know if the HP ring is stronger, but it is run on the stronger drive side when in the front.

[ZOSO]

Ya know I was pondering this myself. What I would do is get a dynatrac axle built. that is if they could work with factory outer knuckles. granted that would probably be $4k.

[Gunnibronco]

Ya know I was pondering this myself. What I would do is get a dynatrac axle built. that is if they could work with factory outer knuckles. granted that would probably be $4k.

Getting into the HP609 price range.

I've been on the Dynatrac page and I know they make one in a 5x5.5 pattern, but it might be the Pro-Rock 60 only.

[Digger]

the HP44 upgrade with the smaller pinion shaft doesn't gain you anything worthwhile.

Howdy digger......can you clarify this for me, I thought the HP Dana 44 gears were somewhere around 25% stronger than the LP Dana 44 gears ?

Maybe the ring gear is stronger but the pinion isn't ?

Yes, high pinion gears are stronger than low pinion. The teeth are cut backwards so the high pinion is pushing on the convex(drive) side of the teeth which is stronger. The low pinion is running backwards and pushing on the concave(coast) side of the teeth.


Dana 44 gears were pretty straight forward for decades. There was low pinion, high pinion and a carrier break for each. Then the Jeep JK came along and screwed up everything. The Jeep JK and JL Dana 44s are not true 44s. They only called them 44s for historical reasons. If they followed typical Dana numbering, the front would be something like a 50-52, the rear would be a 55.

Even the Jeep HD44s are different front to rear. IIRC the front uses a standard 8.5" ring gear with a larger pinion and std 30 spline shafts. The rear uses a 8.9" rear gear with the larger pinion and 32 spline shafts. This may have changed with the JL, but I don't work with a Jeep engineer anymore, so I'm behind the times.

When over-stressed, ring and pinions tend to fail because of pinion gear deflection. Even though pinions are a serious chunk of very high grade heat treated steel, they are projecting 1000's of lb-ft of force a few inches from shaft centerline. The contact forces at the teeth are tremendous. This one of the reasons the Ford 9-inch has the reputation is does, it uses a 3rd bearing to control pinion deflection, making it very strong. So in general its more effective to install a larger diameter pinion vs a larger ring gear.

One other point, I've seen more pinions twisted off at the splines, then gears sets wrecked. And the only way that happened was when both tires were hooking up, otherwise you just break axles and lockouts.

It's a little counter-intuitive, but people tend to break less with lower transfercase gears. Finesse over power I guess.

[Justin]

Interesting. I just got really happy about my doubler.

[Gunnibronco]

It's a little counter-intuitive, but people tend to break less with lower transfercase gears. Finesse over power I guess.

JD said this about swapping to the Atlas4. It surprised me, but it makes sense.

Sent from my E6910 using Tapatalk

[Digger]

It's a little counter-intuitive, but people tend to break less with lower transfercase gears. Finesse over power I guess.

JD said this about swapping to the Atlas4. It surprised me, but it makes sense.

Sent from my E6910 using Tapatalk

With my old rig, I broke 3-4 axle shafts. All heavy throttle and locked diffs. Since I went Atlas, zero broken parts. But I'm more of a finesse style wheeler.

[ZOSO]

It's a little counter-intuitive, but people tend to break less with lower transfercase gears. Finesse over power I guess.

JD said this about swapping to the Atlas4. It surprised me, but it makes sense.

Sent from my E6910 using Tapatalk

Keith one of the Texas guys I rode with last fall was running detroits f/r on a 31spline 9in and d44. With 40's he said once he went atlas 4speed he stopped breaking axles. And with the c4 that thing was freakin killer to wheel. Makes me want a 4sd atlas but cant now.

[Gunnibronco]

The bad news from Carl Jantz is that the ring and pinion I can buy will not fit. The pinion is too short in overall length.

This has confused me, Carl Jantz says there are 2 length of JK pinions. The one I have is a 'short' one at 7-1/2". I've looked at tons of JK ring & pinion sets on line and not one has mentioned short or long pinion. I even spoke to Currie, because this one is from a Currie axle, and they have never heard of different pinion lengths. Based on the part number on the pinion, my guess is it might be from Yukon.

Oh well it was worth a shot.

EDIT: It might be all JK Rubicon front diffs have the "short" pinion. I can't find any with longer pinion. Yukon's and Nitro's both mention short pinion.

[Rox Crusher]

Is Carl Jantz that dude that was on a tv show where they were on some adventure challenge 4x4 trip across Alaska ?

[Gunnibronco]

Is Carl Jantz that dude that was on a tv show where they were on some adventure challenge 4x4 trip across Alaska ?

He might have been. There was some talk of an Alaska trip on one of the Pirate threads.

He has some good Youtube videos about gearing.

[Jesus_man]

With the Atlas there is certainly the opportunity to wheel with more finesse, which is also my style. But when things break, the multiplied torque can really take out of lot of parts.

I had to be dragged out of Penrose (the easy trail) the one time I did it. Running stock HP44 shafts and u-joints I tried to crawl into one of the harder trails and broke the u-joint. So I gave up that idea. When we all started heading back out, I couldn't get a line I needed with 3WD. I maneuvered a little and got the dead wheel bound up against a tree. I could feel the torque was about to overpower my setup so I backed off. Spotter said it would come thru, so I tried again and BOOM, blew the rear atlas yoke and took out the CV. Sweet, 1WD now! That was not so fun.

But since I have upgraded to Chromoly shafts, I haven't had a breakage now that I know the limits of my system.

Then there are times were copious amounts of throttle need applied and I generally cringe in those scenarios.

I too am dreaming about the 609...but I have to get a lot more serious about my wheeling before I can justify that!