Gearing dilemma

[Sacha Rosenthal]

I’m ready to re-gear and was all set on 5.13s for 2005 LJ auto on 35s (they measure about 33ish).

The shop it’s currently in will only warranty their work on 4.88s and that they’ve had problems with 5.13s in the past - chipping etc; I did not press on what and why it happened.

Another shop I spoke to said 4.88s is the best way forward with my setup and 5.13s have too small a pinion; they would not warranty their work on 5.13s either.

I’ve introduced the first shop to Revolution Gears to talk to them as I really want 5.13s. This is based off of all the things I’ve read by Jerry, Chris etc and a quick chat with the guys at Revolution. Thanks All!

I have yet to hear back from them and their chat with Revolution.

What information could I provide the shop with that could get them comfortable with 5.13s?

Depending on the outcome of their call, is it worth me proceeding with 5.13 and no labor warranty (electing to use Revolution gears), or do I suck it up and take the 4.88s with a warranty?

There are no other shops near by (I live near DC) that I can find good recommendations for doing this kind of work.

Help and advice is greatly appreciated!

Thanks!




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[glwood]

I only know that gear (or should I say mechanics who do gears also) shops are notorious for recommending gears that 'go by the book' and turn out to be not enough gear reduction for the tire size and how those who run 35s (or any other plus-sized tires needing a gear change) want them to perform. I would take @Jerry Bransford's real world advice over a shop. There's so many stories of the same thing being recommended and people asking what to do. That is a major modification and expense, and I wouldn't recommend settling for the 4.88 gears just for the warranty, but at the same time, I would insist on a warranty also...where would be the next nearest gear shop you could try outside of DC do you think? Hopefully the shop will get some positive feedback from Revolution.

 

[Chris]

Honestly, I know this probably isn’t what you want to hear, but I would take it to another shop even if it meant driving a ways. 5.13 is the way to go, no question about it. You won’t be happy with 4.88 gears on 35” tires.

 

[jjvw]

Isn't the Revolution 5.13 pinion the same size as the 4.88?

 

[Sacha Rosenthal]

Isn't the Revolution 5.13 pinion the same size as the 4.88?

Yes. That’s what the chaps at Revolution told me. And that’s what I told the shop. I’m hopeful that I can help educate them so they can be open to ‘new’ options!


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[Sacha Rosenthal]

Honestly, I know this probably isn’t what you want to hear, but I would take it to another shop even if it meant driving a ways. 5.13 is the way to go, no question about it. You won’t be happy with 4.88 gears on 35” tires.

Yeah. I may end up there. I’ve looked thru the local jeep association and nothing close. I’d rather not go to too many different states to get this done....


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[Chris]

Yeah. I may end up there. I’ve looked thru the local jeep association and nothing close. I’d rather not go to too many different states to get this done....


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Often times you can find Jeep guys who have a big garage on their property and will do it for you. I had a local guy do it for me. He wasn’t a professional shop, but you could tell he knew what he was doing, and he had a huge lift in his garage. Turned out great too!

 

[jjvw]

From what I've read, there was a time when the experts thought 4.88 was too low and then the pinion would snap. Many also don't understand the nuances of our transmission options. My dad was surprised that I geared as low as I did, for both reasons.

 

[Sacha Rosenthal]

I only know that gear shops are notorious for recommending gears that 'go by the book' and turn out to be not enough gear reduction for the tire size and how those who run 35s (or any other plus-sized tires needing a gear change) want them to perform. I would take @Jerry Bransford's real world advice over a shop. There's so many stories of the same thing being recommended and people asking what to do. That is a major modification and expense, and I wouldn't recommend settling for the 4.88 gears just for the warranty, but at the same time, I would insist on a warranty also...where would be the next nearest gear shop you could try outside of DC do you think? Hopefully the shop will get some positive feedback from Revolution.

Agreed. I’m hoping Revolution can educate them better than I could. I think they’re open to trying something new, but are concerned with performance and don’t want to be on the hook. I understand their concern taking the risk on something as expensive as this is for them. Fingers crossed!


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[jjvw]

Often times you can find Jeep guys who have a big garage on their property and will do it for you. I had a local guy do it for me. He wasn’t a professional shop, but you could tell he knew what he was doing, and he had a huge lift in his garage. Turned out great too!

Same here. My regear was not done "professionally" either.

 

[Sacha Rosenthal]

Often times you can find Jeep guys who have a big garage on their property and will do it for you. I had a local guy do it for me. He wasn’t a professional shop, but you could tell he knew what he was doing, and he had a huge lift in his garage. Turned out great too!

Thats a good idea. I’ll try that route based on my follow up with the shop next week.


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[Sacha Rosenthal]

Same here. My regear was not done "professionally" either.

Perhaps I can get a discount on installation without a warranty!

How would the labor ‘warranty‘ work with your local installation?


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[Jerry Bransford]

Yep, tell that shop to go pound sand since they're too ignorant to know that 5.13 is fine and the more appropriate ratio between it and 4.88. They're just clueless what works and what doesn't. At least use a shop that regularly regears axles, not all do and not all even great mechanics are up to a regearing job. I strongly recommend going with the lubricant recommended by Revolution Gear which is a conventional 85W-140.

And if you had a Rubicon with a front Dana 44 axle, I'd actually be recommending 5.38 as 5.13 is barely enough. But 5.13 is as low as your front Dana 30 can be geared to.

Finally, after my first TJ was stolen, I bought my present TJ with 35" tires and geared to 4.88. With its 4-speed automatic, the same as yours, its highway performance was absolutely abysmal with the 4.88 gears. The engine rpms were so low due to the transmission's VERY steep .69 Overdrive ratio that the engine regularly lugged on the highway & I'd have to turn the Overdrive off to get the rpms up enough. I hated driving it on the highway for that reason.

I got lucky last year and had a great opportunity to regear my Rubicon from 4.88 to 5.38. The Jeep now runs a LOT better on the highway, you can tell the engine is much happier now too. And my mpg went up from just below 12 mpg to over 14 mpg. The best mpg is always obtained when the engine is not lugging/straining so the slightly higher rpms produced by the new 5.38 gearing fixed that. I was shocked that the mpg went up by over 2 mpg after regearing from 4.88 to 5.38 but knowing the engine is happier at the higher rpms, it makes perfect sense.

So while you can't regear to 5.38 due to your front Dana 30 axle, 5.13 is still a much better choice of ratios than 4.88 is.

 

[jjvw]

Perhaps I can get a discount on installation without a warranty!

How would the labor ‘warranty‘ work with your local installation?


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If it breaks, I buy new parts and he'll help me install them. That's the warranty. That was about a year ago, but I'm sure he'll still honor that.

 

[Rob5589]

Both pinions are the same size and have 8 teeth. Those shops are ignorant. They probably said the same shit about anything lower than 4.10 or 4.56 years ago. Revolutions warranty is two years, so they obviously have no problem with the size of the pinion.

 

[Mr. Bills]

I’m ready to re-gear and was all set on 5.13s for 2005 LJ auto on 35s (they measure about 33ish). The shop it’s currently in will only warranty their work on 4.88s and that they’ve had problems with 5.13s in the past . . .

If I were you I would find another shop. Here's why:

(1) The 4.88, 5.13 and 5.38 TJ/LJ Circle K gears sold by Revolution all have the same diameter pinion gear shaft and same number of pinion gear teeth (8). Revolution's gear sets for these three ratios change the number of teeth for the ring gear, not the pinion gear. Although the size of pinion head does vary a bit between the ratios the difference is quite small. [Revolution texted me a photo of the 4.88, 5.13 and 5.38 pinions side by side to prove this, but I can't find the photo as I write this.) The commonly held belief that the pinion gear for 5.13 and 5.38 gear sets is "too small" doesn't apply to the Revolution product.

(2) My experience with gear and axle shops is that they will warranty products from their regular suppliers, are resistant to offering warranties for labor on products from new suppliers, and almost none will warranty labor on customer supplied parts. If you want to use a Revolution gear set and the current shop will not warranty Revolution products you should find a shop that will. My preference would be to find a shop that will offer a warranty on their labor with the Revolution gears because it is far more likely that there will be an install issue that will need to be addressed under warranty than an issue with the gears themselves (regardless of manufacturer/supplier).

(3) Based on the assumption that your '05 LJ auto has the 42RLE automatic transmission and your 35" tires actually measure 34.6" (the typical diameter for a 315/75R15 "metric 35"), you are correct to choose the 5.13:1 gear ratio for your non-Rubicon axles. (You will be even more correct with 5.13's if your tires are "33ish" rather than 34.6".) Although 5.38 might be even better yet, that ratio isn't currently available for your non-Rubicon axles.

I base my opinion primarily upon my observations while driving my gear installer's '05 LJ auto with 35" ties and 5.13 gears, driving my own '06 LJ Rubicon auto with 35" tires 4.88 gears (as equipped when purchased by me), and later by driving my '06 LJ Rubicon auto with 35'" tires after re-gearing to 5.38 Revolution gears.

 

[Drizit]

4.88s are great if you have a stick, with the auto you need all the gear you can get. My axles came 5.13 and with 35s they were great. With 37s I'm in 3rd gear all the time on the highway. This would be a similar situation for you with 35s and 4.88s, don't settle till you find a shop that will install the gears with a warranty.

By the way its been my experience that most gear manufacturers don't honor warranties, they just blame any failure on setup regardless of the facts. So if you get a parts and labour warranty chances are the shop is eating the cost of the second set of gears.

—
There must have been a time
when we could have said no.

 

[Jerry Bransford]

By the way its been my experience that most gear manufacturers don't honor warranties, they just blame any failure on setup...

The reason for that is most gear failures are indeed caused by poor setup, improper or lack of break-in, wrong lubricant, etc. but not the gears themselves. Like the idiots who slam into someone's car who claim their brakes "went out". Right.

 

[Drizit]

The reason for that is most gear failures are indeed caused by poor setup, improper or lack of break-in, wrong lubricant, etc. but not the gears themselves. Like the idiots who slam into someone's car who claim their brakes "went out". Right.

Quite likely, although I've yet to hear of them acctualy honoring a warranty for any of the local shops no matter what documentation is provided. Seems a bit silly to even brag about the warranty period when no one can get it honored.

—
There must have been a time
when we could have said no.

 

[Jerry Bransford]

Quite likely, although I've yet to hear of them acctualy honoring a warranty for any of the local shops no matter what documentation is provided. Seems a bit silly to even brag about the warranty period when no one can get it honored.

I know personally that Revolution Gear honors their gear warranties when they can reasonably believe they were installed correctly.