Re-gearing question: 37's with 5:13 or 4:88 gears?

[JD101]

i am going 4.88 as advised by the jeep dealer and the performance drivetrain shop doing the job. I dont tow anything nor do i plan on it and i also watched to many videos of overheated rears and lower gas mileage from people that went 5.13 gears and had to replace them after a year due to failure.

This makes zero sense to me . Chalk that up to a bad install. I've driven form Detroit to Colorado springs at 80 pretty much entire way , wheeled and drove back 80 . Zero issues .

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[Escape.idiocracy]

Is this legit? Like actual problems just from 5.13.. seems like there has been a lot of people with that gear installed.

This should be a fun one.
It can be ligit… this is why KOH and desert race trucks run circulation pumps and differential coolers. High cut gears run hotter… Curries Notes on fluid and warranty

I have run 5.13’s and traveled from the Mojave area of California to tri cities Washington on several trips with no more than watering a fuel breaks….70~ miles an hour the entire way through more times than I want to think of without issues.

Deep gears need regular fluid change…. 10k if towing and running hard. 15k normal use. My $0.02

 

[kennyglm]

Most of the videos i watched on youtube initially said how great the 5.13s were at first and later did a new video 6 months or a year later of them having to regear again because of catastrophic failure due to stripped pinion gears and overheating of the differentials. The videos are very misleading because they dont follow up with there original video. I will stick with the 4.88s as advised by the drivetrain shops.

 

[kennyglm]

This should be a fun one.
It can be ligit… this is why KOH and desert race trucks run circulation pumps and differential coolers. High cut gears run hotter… I’ll add that Currie will not warranty their rears unless a GL5 fluid is used….. which I’m pretty certain most of not all GL5 fluid is natural and not synthetic… only sense I can make of it is maybe heat soak and dissipation is different…. Figure synthetic would be better but they must think otherwise….

I have run 5.13’s and traveled from the Mojave area of California to tri cities Washington on several trips with no more than watering a fuel breaks….70~ miles an hour the entire way through more times than I want to think of without issues.

Deep gears need regular fluid change…. 10k if towing and running hard. 15k normal use. My $0.02

thank for trying to clear this up.

 

[AustinL911]

5.13 and never looked back . 1000s of miles driven from sea level to 14000' . Flat to mountains , rocks to mud and sand . I would have regretted 4.88s . There is no argument for 4.88s IMO . At least in a gladiator. 5.13s are like 4.88s with some reserve for towing , elevation , wind , ect.

If you like 4.88 that's cool too. Not bashing that choice . I like 5.13s and from my experience I haven't seen a downside .

I will add that you could go from a 37 to a 35 if ever needed with 4.88s the opposite is true for 5.13s . I was going to take the 35s off our JL and strap them on just for kicks one day .

I pretty much have full intentions of running 5.13 with my 35" STT Pros and my 6MT. I won't tag 3000rpm in 6th until 83mph. That's fast enough for me. I typically run <70mph.

The 3.6 loves to spin so I'm going to oblige it. We'll see how it goes...

 

[Wheelin98TJ]

This should be a fun one.
It can be ligit… this is why KOH and desert race trucks run circulation pumps and differential coolers. High cut gears run hotter… I’ll add that Currie will not warranty their rears unless a GL5 fluid is used….. which I’m pretty certain most of not all GL5 fluid is natural and not synthetic… only sense I can make of it is maybe heat soak and dissipation is different…. Figure synthetic would be better but they must think otherwise….

I have run 5.13’s and traveled from the Mojave area of California to tri cities Washington on several trips with no more than watering a fuel breaks….70~ miles an hour the entire way through more times than I want to think of without issues.

Deep gears need regular fluid change…. 10k if towing and running hard. 15k normal use. My $0.02

Currie explains their fluid choice here:

https://www.currieenterprises.com/why-run-conventional-gear-oil

Most of the videos i watched on youtube initially said how great the 5.13s were at first and later did a new video 6 months or a year later of them having to regear again because of catastrophic failure due to stripped pinion gears and overheating of the differentials. The videos are very misleading because they dont follow up with there original video. I will stick with the 4.88s as advised by the drivetrain shops.

Bad gear setups.

There are tons of people running 5.13 and 5.38 with no problems. People have been running these ratios in street driven Jeeps since overdrive transmissions came out.

 

[Elff]

Currie explains their fluid choice here:

https://www.currieenterprises.com/why-run-conventional-gear-oil

If you read that, it is very very very specfic to the Ford 9" Rear

The 9-Inch Gear Is Unique
The design of the 9-inch features a high-offset distance that places the center-line of the pinion gear 2.25-inches below the center-line of the ring gear, which is substantial when compared to the 1.125 to 1.5-inch offsets of other gear sets (see image below). The high-offset distance increases the contact patch between the ring and pinion teeth by approximately 30-percent and is a crucial reason for the legendary strength of the 9-inch gears. However, strength comes at a price, as this high-offset distance creates increased sliding friction and heat across the gear tooth face. Because of this, not using high-shear oil such as Currie’s 85/140w can lead to scoring and certain gear death, especially during extreme scenarios such as off-roading and racing.

Our Dana Axles are physically different. The above however, is probably a good idea for people who tow and do a lot of long distance driving. It definitely would not do anything bad.

Personally, I like 4.88s with 37s on my TJ. I have a 5 speed Manual.
It gives me a 78:1 Crawl ratio as I have a 4.02 first gear and 4:1 T-case.
Previously, in my first TJ, I had a 5:1 Atlas T-Case which pushed my first gear crawl ratio to 98:1
In my first jeep there were so many situations where I just did not use first gear, and my top speed in 4Lo was lower due to the fact that I revved out sooner.
I am primarily an East Coast Wheeler, and used to compete in 4-6 Rock Crawling competitions a year.

On the Street my 5th gear is .78, which is between the Gladiator's 7th and 8Th gear ratios of
.84 and .67 respectively. As such, In 8th gear, with 4.88s, I feel like the RPMs for cruising would be really good and no impact gas mileage too much, and on hills, with 4.88s you could drop into 7th if you found that you were not maintaining speed.

So in my experience, I personally would not like 5.13s for either the street or rock crawling.
[Please Note: This is my opinion from about 80,000 miles of driving and rock crawling experience]

 

[kennyglm]

Currie explains their fluid choice here:

https://www.currieenterprises.com/why-run-conventional-gear-oil


Bad gear setups.

There are tons of people running 5.13 and 5.38 with no problems. People have been running these ratios in street driven Jeeps since overdrive transmissions came out.

Well this is just my opinion i am not saying its right or wrong but i am going to take the advice of the drivetrain shop over a few youtube videos that most likely are being sponsored by the products they use. At $ 3,000.00 to swap the gears and program the speedo i wanna make sure i get it right the first time. I am also using dana gears and not yukons from china.

 

[hjdca]

I have a stick shift JTR with Dana Spicer 5:13s and 37s and about 25K miles on them. I live in the west coast mountains and go fast on the fwy. I have done the Rubicon and the 3 badge of honor Big Bear trails a few times and lots of 4wheeling around where I live. I love the setup, especially with the 4:1 Rubicon transfer case. Granny gear is fantastic. I have never, not once, thought that I should have gone with 4:88s. No problems so far. I am running the Metalcloak diff covers, and I run the Mopar 140 weight gear oil in both diffs. I have changed the fluid a few times already, and there was just a little bit of metal powder on the magnet for the rear diff the first few changes. I never tow.

 

[Wheelin98TJ]

If you read that, it is very very very specfic to the Ford 9" Rear

There are many references to the 9", however it applies to all Currie axles.

 

[TheRealGinjaNinja]

Well this is just my opinion i am not saying its right or wrong but i am going to take the advice of the drivetrain shop over a few youtube videos that most likely are being sponsored by the products they use. At $ 3,000.00 to swap the gears and program the speedo i wanna make sure i get it right the first time. I am also using dana gears and not yukons from china.

Good call going with Dana Spicer!

 

[Wheelin98TJ]

Well this is just my opinion i am not saying its right or wrong but i am going to take the advice of the drivetrain shop over a few youtube videos that most likely are being sponsored by the products they use. At $ 3,000.00 to swap the gears and program the speedo i wanna make sure i get it right the first time. I am also using dana gears and not yukons from china.

Maybe I misunderstood, I thought those YouTube videos helped justify your choice of 4.88 over 5.13.

You cited videos talking about 5.13 failures.

I wouldn't put any faith in those videos.

Good choice on gears. ?

 

[kennyglm]

Maybe I misunderstood, I thought those YouTube videos helped justify your choice of 4.88 over 5.13.

You cited videos talking about 5.13 failures.

I wouldn't put any faith in those videos.

Good choice on gears. ?

Oh heck ya i watched alot of youtube videos to confuse me lol thats how i found the follow up videos of the failed 5.13s. When i came to my senses i figured it would be best to trust the drivetrain shop thats been in business over 30 years and also the jeep dealership . They both specialize in lifted jeeps. They both told me 4.88s will be slightly better than a stock rubicon and this is what i am looking for.

 

[be77solo]

I pretty much have full intentions of running 5.13 with my 35" STT Pros and my 6MT. I won't tag 3000rpm in 6th until 83mph. That's fast enough for me. I typically run <70mph.

The 3.6 loves to spin so I'm going to oblige it. We'll see how it goes...

This right here for the 6MT setups... I agree completely! My plan is 5.13's. Currently running KO2 "35's", and by all accounts and playing with gears/speeds think 5.13's will rock!

So many threads about gears either don't account for the manual transmission, or interchange info like it's the same, which it is not. Thanks for bringing this up.

 

[TheRealGinjaNinja]

Just pulled the trigger on this myself finally...5.38s (Dana Spicer) going in in ten days ;-)

Sucks how expensive it is in my area but the longer I wait the more it costs ($3,215) but alas...will be worth it!

Cheers

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