Gears for JKU Rubicon with 3.6 engine and 6-speed tranny

JoeB-JKURX · Nov 21, 2017

I know (expect) that this question has been asked and answered more than once on this forum but I couldn't find this specific combination. In any case, I'm ready to go from 35s to 37s (been running the stock 4.10s with the 35s and it seems to do alright). The Cs have gussets and I've got chromalloy axle shafts. I do some pretty serious rock crawling but nothing at speed. Is there a good reason not to go with 4.88s (but to go to 5.13s) given the 4 to 1 transfer case?

WJCO · Nov 21, 2017

Regearing will likely be a good power balance but if you're going to get the 37s anyways, I say try it and see what you think. I'm currently in Albuquerque and it seems pretty flat around here, not sure where you guys wheel at. If not a lot of hills, you may be just fine.

But if you're going to regear anyways, I would say 5.13s. Tool and Passenger weight alone adds stress on the vehicle. I wish now that I had gone up one more ratio based on what I carry.

DWiggles · Nov 21, 2017

I have 5.13s in my JKUR, 6 speed manual, 37s... It's nearly perfect.
4.88 will get a little better mileage, but at the end of the day, we are talking about 200rpms... dive in and never look back.

sent from SPACE!
DZZ Build thread

MacRubi2 · Nov 21, 2017

I’m going to re-gear and add CM axles the first of the year.

Currently I thought the norm was 5.13 for the auto and 4:88 for a stick

I seem to get this picture in my head of a 5:13 D30 R&P and the lack of teeth

Is it really that bad on the D44 to run a 5:13 gear or you really don’t loose any significant strength until 5:38’s

NevadaZielmeister · Nov 21, 2017

JoeB-JKURX said:
I know (expect) that this question has been asked and answered more than once on this forum but I couldn't find this specific combination. In any case, I'm ready to go from 35s to 37s (been running the stock 4.10s with the 35s and it seems to do alright). The Cs have gussets and I've got chromalloy axle shafts. I do some pretty serious rock crawling but nothing at speed. Is there a good reason not to go with 4.88s (but to go to 5.13s) given the 4 to 1 transfer case?

No, you need to get a turbo.

Just kidding. Actually, since you do "some pretty serious rock crawling" I would recommend go 5.38. Then when you eventually move to 40's, you will still be okay. I run 5.38 on 37's and feel no detriment to my off-roading.

JKDream · Nov 22, 2017

NevadaZielmeister said:
No, you need to get a turbo.

Just kidding. Actually, since you do "some pretty serious rock crawling" I would recommend go 5.38. Then when you eventually move to 40's, you will still be okay. I run 5.38 on 37's and feel no detriment to my off-roading.

I don't know about you but I wouldn't put 5:38's in a 44, and I certainly wouldn't run 40's on them.

Parks34 · Nov 22, 2017

JoeB-JKURX said:
I know (expect) that this question has been asked and answered more than once on this forum but I couldn't find this specific combination. In any case, I'm ready to go from 35s to 37s (been running the stock 4.10s with the 35s and it seems to do alright). The Cs have gussets and I've got chromalloy axle shafts. I do some pretty serious rock crawling but nothing at speed. Is there a good reason not to go with 4.88s (but to go to 5.13s) given the 4 to 1 transfer case?

4.88 gears will put you right about stock with 37's

Sent from my iPhone using WAYALIFE mobile app

NevadaZielmeister · Nov 22, 2017

JKDream said:
I don't know about you but I wouldn't put 5:38's in a 44, and I certainly wouldn't run 40's on them.

Really? I have had no issues at all. And running 40's on a ProRock 44? Why not?

https://wayalife.com/showthread.php/31459-Rubicat-on-40-s-FLEX-TEST

But I defer to the experts like Eddie regarding what is best. While I have no plans to run 40's right now, I might upgrade the front Axle to match my XD60 rear. But thanks for caring.

JKDream · Nov 22, 2017

NevadaZielmeister said:
Really? I have had no issues at all. And running 40's on a ProRock 44? Why not?

https://wayalife.com/showthread.php/31459-Rubicat-on-40-s-FLEX-TEST

But I defer to the experts like Eddie regarding what is best. While I have no plans to run 40's right now, I might upgrade the front Axle to match my XD60 rear. But thanks for caring.

Cool, I'm sure he'd tell you the same thing I just did. But what do I know.

NevadaZielmeister · Nov 22, 2017

JKDream said:
I don't know about you but I wouldn't put 5:38's in a 44, and I certainly wouldn't run 40's on them.

And can you please find me a broken ProRock 44 housing? I have never seen or heard of anything like that. And how about ring and pinion failure?

Well, the quote another expert, Dynatrac:

"To date, we've found 1 front 44 JK gear failure- period. This covers any size tire or gear ratio. I'm sure there must be more but they aren't easy to find and people aren't talking about them.

The JK 44 front gear is a larger ring gear (8.8" vs 8.5") version of the older 44 and also has a larger pinion shaft. It has proven to be very durable. We are very comfortable recommending this gear for 37" tires (and maybe larger depending on the application)."

So you tell me, what are you hearing and what are you breaking?

JKDream · Nov 22, 2017

NevadaZielmeister said:
And can you please find me a broken ProRock 44 housing? I have never seen or heard of anything like that. And how about ring and pinion failure?

Well, the quote another expert, Dynatrac:

"To date, we've found 1 front 44 JK gear failure- period. This covers any size tire or gear ratio. I'm sure there must be more but they aren't easy to find and people aren't talking about them.

The JK 44 front gear is a larger ring gear (8.8" vs 8.5") version of the older 44 and also has a larger pinion shaft. It has proven to be very durable. We are very comfortable recommending this gear for 37" tires (and maybe larger depending on the application)."

So you tell me, what are you hearing and what are you breaking?

You are going off topic. I called you out because OP has a stock Rubicon. Who said anything about ProRock 44's?
Seeing as OP has a rear 44 as well, and I'm not talking about you, here's a photo of what happened to a rear set of 5:38's.

NevadaZielmeister · Nov 22, 2017

JKDream said:
You are going off topic. I called you out because OP has a stock Rubicon.

Does he? I didn't read that in his post and really we are left to assume.

JKDream said:
Who said anything about ProRock 44's? Seeing as OP has a rear 44 as well, and I'm not talking about you, here's a photo of what happened to a rear set of 5:38's.

Nobody, but then again, I see that you are stating that would not run 5.38's as a pretty much blanket statement. In reading your profile, can't tell what kind of axles you are running either. It is good to give the OP some more information out there with some choices besides JUST what gear to chose. In my humble opinion, going with a gear higher than 4.88 would not be smart in a stock Rubicon axle.

JKDream said:
View attachment 283646

Cool photo. I can't remember where that was from. Can you give us specifics? Maybe the link? As the photos shows a ruined ring gear from somewhere. It would be good to have specifics.

And relax Canuck, there is no need for anyone to call anyone out here with big old huge gotcha statements. We are all here to help the OP. I am just not interested in arguing on this fine day.

JKDream · Nov 22, 2017

NevadaZielmeister said:
Does he? I didn't read that in his post and really we are left to assume.

JoeB-JKURX said:
The Cs have gussets and I've got chromalloy axle shafts.

It's pretty clear to me.

NevadaZielmeister said:
Cool photo. I can't remember where that was from. Can you give us specifics? Maybe the link? As the photos shows a ruined ring gear from somewhere. It would be good to have specifics.

Don't worry, I've got you.

wayoflife said:
Blown out rear end also compliments of the Dusy Ershim. Should have known better than to run a 5.38 ring & pinion in a Dana 44 rear axle pushing 40x15.50's...

NevadaZielmeister said:
And relax Canuck, there is no need for anyone to call anyone out here with big old huge gotcha statements. We are all here to help the OP. I am just not interested in arguing on this fine day.

Cool as a cucumber, no arguments over here. Just calling it as I see it.

wayoflife · Nov 22, 2017

LOL!! Haven't been following the thread but got a push notification saying that I had been quoted. The photo in question is my old 5.38 ring gear out of the Dana 44 I was running back in the day. This was way back before we knew any better. :crazyeyes:

NevadaZielmeister · Nov 22, 2017

wayoflife said:
LOL!! Haven't been following the thread but got a push notification saying that I had been quoted. The photo in question is my old 5.38 ring gear out of the Dana 44 I was running back in the day. This was way back before we knew any better. :crazyeyes:

Now correct me if I'm wrong, but didn't you do a video of that out on the trail? I remember that one since it was what prompted me to carry extra axle gear oil in my kit just in case I had a leak or something. Again, learning from your mistakes my friend.

I agree with JKDream in that you would not want to run a 5.38 on STOCK Rubi 44 axles. That being said, getting better axles would be the best option for running 37 inch tires. Can we at least agree on this?

wayoflife · Nov 22, 2017

NevadaZielmeister said:
Now correct me if I'm wrong, but didn't you do a video of that out on the trail? I remember that one since it was what prompted me to carry extra axle gear oil in my kit just in case I had a leak or something. Again, learning from your mistakes my friend.

I agree with JKDream in that you would not want to run a 5.38 on STOCK Rubi 44 axles. That being said, getting better axles would be the best option for running 37 inch tires. Can we at least agree on this?

Yep, it's on our Dusy video. Not sure what we're agreeing or disagreeing to but in my opinion, 5.38 in a Dana 44 is definitely a bad idea especially if you're gonna run big tires and play hard. It's the right ratio for 40's but the pinion is way small and on a high pinion rear axle, you're running on the weak side of the gears.

wayoflife · Nov 22, 2017

Okay, just caught up on the thread. A Dana 44, ProRock 44 or any 44 for that matter will all have the same size ring and pinion. For the most part, that's what makes a 44 a 44. Again, 5.38 is the right ratio for 40" tires but on a 44, that'll leave you with a very small pinion and one that basically has just one tooth on the ring gear. Not exactly the strongest setup in the world. Also, as I had mentioned, on a high pinion rear axle, you will be running on the coast side of the ring gear and that will be weaker. Depending on how hard you play, this weakness would also apply to a high pinion rear 60 and I have seen plenty of those break too. With all that said, speed will break things way more than any rock crawling could ever hope to so there's that.

NevadaZielmeister · Nov 22, 2017

wayoflife said:
Okay, just caught up on the thread. A Dana 44, ProRock 44 or any 44 for that matter will all have the same size ring and pinion. For the most part, that's what makes a 44 a 44. Again, 5.38 is the right ratio for 40" tires but on a 44, that'll leave you with a very small pinion and one that basically has just one tooth on the ring gear. Not exactly the strongest setup in the world. Also, as I had mentioned, on a high pinion rear axle, you will be running on the coast side of the ring gear and that will be weaker. Depending on how hard you play, this weakness would also apply to a high pinion rear 60 and I have seen plenty of those break too. With all that said, speed will break things way more than any rock crawling could ever hope to so there's that.

Do your comments hold true for the XD60 the same as the regular ProRock 60 regarding ring/pinion stresses? Just wanted to clarify.

wayoflife · Nov 22, 2017

NevadaZielmeister said:
Do your comments hold true for the XD60 the same as the regular ProRock 60 regarding ring/pinion stresses? Just wanted to clarify.

The XD60 has an even larger ring and pinion so a high pinion rear would be stronger - it should be more than adequate for 40" tires. Now, if you were running an LS on top of that, I would probably still recommend a standard cut XD60 or ProRock 80.

SDG · Nov 23, 2017

NevadaZielmeister said:
And can you please find me a broken ProRock 44 housing? I have never seen or heard of anything like that. And how about ring and pinion failure?

Well, the quote another expert, Dynatrac:

"To date, we've found 1 front 44 JK gear failure- period. This covers any size tire or gear ratio. I'm sure there must be more but they aren't easy to find and people aren't talking about them.

The JK 44 front gear is a larger ring gear (8.8" vs 8.5") version of the older 44 and also has a larger pinion shaft. It has proven to be very durable. We are very comfortable recommending this gear for 37" tires (and maybe larger depending on the application)."

So you tell me, what are you hearing and what are you breaking?

I have seen a broken R&P on a rear 60 running 40s in person... so it would be all that more true on a 44.

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