5.29's with High Range Under-drive T-case Gears (1 Viewer)

[baldilocks]

Correct me if I’m wrong. From what I’ve read, the high range UD is added to the low range when engaged. If so, then the low range gearing is about the same either way.

The parts are already in hand. Almost a year ago, I bought 4.88’s, high range, and low range gears with the thought that 4.88’s would be slightly stronger than 5.29’s. Parts delays from Australia have delayed the build for over 7 months, so I’ve had too much time to think “What if.”

I want to gear down as low as possible for crawling. The recent Doubler/Black Box thread comments and desires to gear way down got me thinking 5.29’s might work out better than 4.88’s.

Now I know that isn’t in my best self interest.

View attachment 2582890

Also, if you, or the next owner, decide the gearing is too low on the road for some crazy reason, like dropping to smaller tires, going back to the stock high range gear in the xfer case is cheaper and easier.

 

[ThreeEyedBandit]

Correct me if I’m wrong. From what I’ve read, the high range UD is added to the low range when engaged. If so, then the low range gearing is about the same either way.

The parts are already in hand. Almost a year ago, I bought 4.88’s, high range, and low range gears with the thought that 4.88’s would be slightly stronger than 5.29’s. Parts delays from Australia have delayed the build for over 7 months, so I’ve had too much time to think “What if.”

I want to gear down as low as possible for crawling. The recent Doubler/Black Box thread comments and desires to gear way down got me thinking 5.29’s might work out better than 4.88’s.

Gotcha on the parts being on hand.

You do get some of the gearing of the under drive gearset, but it's only approx 6.5%. ~1.065:1.

I really want to try the Blackbox out also, but last I looked it is $1500 plus almost 700 for the proper shafts which they don't speak of on the website. And after having some locals have issues and no real support I'd pass.

 

[baldilocks]

Gotcha on the parts being on hand.

You do get some of the gearing of the under drive gearset, but it's only approx 6.5%. ~1.065:1.

I really want to try the Blackbox out also, but last I looked it is $1500 plus almost 700 for the proper shafts which they don't speak of on the website. And after having some locals have issues and no real support I'd pass.

This is the first I’ve heard of your math. Would you elaborate on this 1.065:1?

 

[GW Nugget]

Most calcs are off... I had to put in 34.9" to match my 37s actual RPMs after my 488 gear install. I had to go with the 10% underdrive gears to make up for the misscalculation. Final is 536 now. I run 38s now & speedo matches GPS speed which means Im back to stock pefectly.

To do 80 down the road all day every day go 488 but 529s if you do freeway stuff once in awhile to get to a trail.

 

[ThreeEyedBandit]

This is the first I’ve heard of your math. Would you elaborate on this 1.065:1?

I should clarify, UD gearset is 6.5% lower in low range than the stock gearset.

Stock idler(39t)/stock input(33t) ~ 1.182:1

UD idler(39t)/UD input(31t) ~ 1.258:1

1.258/1.182 = 1.065

Where in high range the UD set output(34t)/input(31t) gets you 1.097.

At least according to the tooth count on the gearsets done by cruiser outfitters.

That's how my brain maths it out.

 

[baldilocks]

I should clarify, UD gearset is 6.5% lower in low range than the stock gearset.

Stock idler(39t)/stock input(33t) ~ 1.182:1

UD idler(39t)/UD input(31t) ~ 1.258:1

1.258/1.182 = 1.065

Where in high range the UD set output(34t)/input(31t) gets you 1.097.

At least according to the tooth count on the gearsets done by cruiser outfitters.

That's how my brain maths it out.

I was unaware that stock high range was not simply 1:1. Thanks

 

[ThreeEyedBandit]

I was unaware that stock high range was not simply 1:1. Thanks

Stock high range is 33:39:33, 1:1

UD is 31:39:34, 1.097:1

Power for low range gets split off before the the final compound, think that's the part that gets overlooked.

 

[jcardona1]

I should clarify, UD gearset is 6.5% lower in low range than the stock gearset.

Stock idler(39t)/stock input(33t) ~ 1.182:1

UD idler(39t)/UD input(31t) ~ 1.258:1

1.258/1.182 = 1.065

Where in high range the UD set output(34t)/input(31t) gets you 1.097.

At least according to the tooth count on the gearsets done by cruiser outfitters.

That's how my brain maths it out.

That sounds right because they said the lowest possible gearing you can get with the low range + high range UD gears is 3.31:1 which = 3.11 x 1.065

 

[Road Apple]

Why not go stock high range/3.1/5.29s? That should be slightly taller high range, and lower low range than the UD high/3.1/4.88s

After thinking this discussion overnight, I ran the numbers again and came up with the same conclusion. You're right. This would be the best compromise between highway and offroad gearing. The UD gears don't help much in low range, so they aren't worth the expense unless you want high range gearing adjustment.

 

[Shipwreck]

After thinking this discussion overnight, I ran the numbers again and came up with the same conclusion. You're right. This would be the best compromise between highway and offroad gearing. The UD gears don't help much in low range, so they aren't worth the expense.

I came to the same conclusion a couple years ago when I was installing my low range transfer case gears. I thought about the high range UD gears but after running the numbers it would increase my freeway rpms too much on the flats. Might be good if you are climbing hills all the time, but I had to be honest with myself. 80-90% of the time I'm cruising around town or driving to work on the freeway.
I still have 4.88s for some of the same reasons that you mentioned; arguably stronger than 5.29's and puts the speedo almost dead-on with 37's. No need for speedo correction. If you already have 4.88s installed, I don't think the difference is worth the expense and effort to change to 5.29's. If you haven't got them installed; then go for it.
Basically, if you are planning to drive this to the Sierras to wheel tough trails and drive home again, I would optimize the freeway driving. No matter what you do about changing TC gears or differential gears will not make a huge difference in your ability to have fun and be successful on the trail. It is not a "game changer" like having dual cases. Yes, it helps, but at the end of the day, these are big heavy-assed trucks with a big overhang in the rear and lots of sheet metal and glass. Size and weight will be the biggest influence on navigating trails like the Rubicon.
I'm fairly local to you and get over the hill to Santa Cruz fairly often, so if you want to get an idea of what 37s/3.11/4.88 combo drives like, shoot me a pm and I'd be happy to let you test drive.

 

[General Grant]

I’m in Central California on 37’s, 5.29’s and a factory case. Going to install low range gears. I’ve driven an 80 with 5.29’s and low range under drive in the rocks at elevation and it’s still not low enough. My cruiser turns a lot more RPM than ever at highway speeds, but i never drive over 75mph on the interstate. I may look into the high range overdrive to get the high range closer to factory

 

[baldilocks]

I came to the same conclusion a couple years ago when I was installing my low range transfer case gears. I thought about the high range UD gears but after running the numbers it would increase my freeway rpms too much on the flats. Might be good if you are climbing hills all the time, but I had to be honest with myself. 80-90% of the time I'm cruising around town or driving to work on the freeway.
I still have 4.88s for some of the same reasons that you mentioned; arguably stronger than 5.29's and puts the speedo almost dead-on with 37's. No need for speedo correction. If you already have 4.88s installed, I don't think the difference is worth the expense and effort to change to 5.29's. If you haven't got them installed; then go for it.
Basically, if you are planning to drive this to the Sierras to wheel tough trails and drive home again, I would optimize the freeway driving. No matter what you do about changing TC gears or differential gears will not make a huge difference in your ability to have fun and be successful on the trail. It is not a "game changer" like having dual cases. Yes, it helps, but at the end of the day, these are big heavy-assed trucks with a big overhang in the rear and lots of sheet metal and glass. Size and weight will be the biggest influence on navigating trails like the Rubicon.
I'm fairly local to you and get over the hill to Santa Cruz fairly often, so if you want to get an idea of what 37s/3.11/4.88 combo drives like, shoot me a pm and I'd be happy to let you test drive.

Now there’s a whole lot of honesty born of common sense and experience.