Re-gearing advice for 35s, 42RLE transmission, and lockers

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Mr. Bills said:
Looks like 5.38 gears for the TJ Dana 30 were a false alarm.
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It does appear that way.. I figured I would dig it up but I couldn't find anything about this one or any other fitting a TJ. Too bad. It would have been nice for 42rle folks with dana 30s
 
Not trying to step on your toes there buddy. I don’t doubt that you know what your talking about but there again, I could doubt (or not) anything; that’s why we inquire. There’s a lot of info out there & most from those who know just enough to be dangerous. The D-bag that did my gears wrong is supposed to be an “expert!” “Been buildin Jeep drivetrains for 30 years!” While the rubi may be the same in high, I don’t have one (Rubi) so never researched the t-case. All I know is it’s different than mine & mine is what I’m trying to figure out. Don’t take offense to any of the above, I’m just speaking frankly (including the D-bag drivetrain “expert”. In short, I had read Ryan’s post & thought “that’s my set up!” FWIW, I called 4 drivetrain shops today & 3 of 4 said 3.15 is too low. Again, not arguing but, you can see where the frustration can come in. Peace.
 
@Mr. Bills, I should add that I ran the calcs on grimm Jeeper before regear & 4.56 was close to stock. That may be where I went wrong. I was thinking I should shoot for getting as close to stock as possible & not knowing to give consideration to adjust for rolling resistance : powerband. Again, there’s a lot of info out there; even good that can be misleading.
 
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What would the difference feel like going from 3.73 to the 5.38 gears? Is it going to ride rough? I'm having a hard time understanding the difference I would feel between the two. Local 4wd parts store recommended 4.11 for my TJU (35s with 42lre transmission). He recommended this because it would be my daily driver.

What is fact here?

Do I really want to go as steep as the 5.38? Is it going to make the vehicle drive like a dog? Why would the 4wd place suggest 4.11 for a "daily driver"?
 
What would the difference feel like going from 3.73 to the 5.38 gears? Is it going to ride rough? I'm having a hard time understanding the difference I would feel between the two. Local 4wd parts store recommended 4.11 for my TJU (35s with 42lre transmission). He recommended this because it would be my daily driver.

What is fact here?

Do I really want to go as steep as the 5.38? Is it going to make the vehicle drive like a dog? Why would the 4wd place suggest 4.11 for a "daily driver"?
 
Noprisonersnick said:
What would the difference feel like going from 3.73 to the 5.38 gears? Is it going to ride rough? I'm having a hard time understanding the difference I would feel between the two. Local 4wd parts store recommended 4.11 for my TJU (35s with 42lre transmission). He recommended this because it would be my daily driver.

What is fact here?

Do I really want to go as steep as the 5.38? Is it going to make the vehicle drive like a dog? Why would the 4wd place suggest 4.11 for a "daily driver"?
Click to expand...

The 4wd shop doesn't understand gearing and why the transmission matters. One can run the numbers on grimmjeeper.com, but the problem with 35s/42rle and only 4.10 gears is that you will shift into OD far too early without enough rpm and power at a significantly lower speed than if you had 5.38. you can survive on the band-aid fix of not using the OD. But the point of regearing is to make the most use of your transmission for the chosen tire size.
 
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Noprisonersnick said:
What would the difference feel like going from 3.73 to the 5.38 gears? Is it going to ride rough? I'm having a hard time understanding the difference I would feel between the two. Local 4wd parts store recommended 4.11 for my TJU (35s with 42lre transmission). He recommended this because it would be my daily driver.

What is fact here?

Do I really want to go as steep as the 5.38? Is it going to make the vehicle drive like a dog? Why would the 4wd place suggest 4.11 for a "daily driver"?
Click to expand...
As above, that shop doesn't understand your 42RLE's effect on what would be the correct gear ratio. 4.11 would be fine for 35" tires with a manual transmission and a big V8 engine. With the 4.0L engine and 5-speed with 35" tires, you need 4.88 to 5.13 gears for it to run well. With the 42RLE, whose Overdrive ratio is .69 which lowers the engine rpms WAY down on the highway, you want a minimum of 5.13 but 5.38 is preferrable.

What you would notice on the road with 4.11 gears and your 42RLE is your TJ's performance would be absolutely TERRIBLE... no power and the engine would lug badly on the highway when in Overdrive. It would actually still lug even with the Overdrive shut off. Not to mention your engine would be operating so inefficiently at the low rpms that 4.11 would create that your mpg would be terrible.

I bought my second TJ used with 35's, the 42RLE, and it had 4.88 gears. It was a dog on the highway and the engine lugged. It never quite got to even 12 mpg. The mpg was always in the high 11's. Then I had an opportunity to replace the 4.88 gears with 5.38 and suddenly the sun came out from behind the clouds. The engine was just happier at the slightly higher rpms and my highway mpg even went from sub-12 to 14.6. And even at 70 mph, its rpms at around 2650 are not even close to being too high. They're actually slightly slower than the 2750 at 70 mph I enjoyed with my previous TJ with its 5-speed transmission, 4.88 gearing, and 35" tires. I actually wish I could have gone slightly deeper than 5.38 to get just a tad higher highway rpms like I had with my previous TJ when it had its 5-speed.

Trust us when we say you would HATE HATE HATE your TJ's driving characteristics, mpg, and performance with 4.10 gearing with 35's and your 42RLE transmission.

In other words, stop listening to that shop. They don't know what they're talking about when it comes to gearing for a TJ running the 42RLE transmission.
 
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I just bought my LJ with 35s and the stock 3.73 gears. It sucked hard. One of the first things I did was regear to 5.13s. I have the Dana 30 so I couldn't go lower. It is MUCH better! As far as what to expect:

- Better acceleration from a stop. Big tires and stock gears is like starting in 2nd gear all the time.
- You can actually use the overdrive on the highway.
- Better acceleration when you downshift to pass somebody or merge on the highway.
- Better gas mileage.
- Better for towing a small camper or trailer.
- Better for off road.

I'm trying to think of drawbacks. If you like to go 90 mph on the highway you're going to be revving higher, but why are you going that fast in a Jeep? Although I used to live in Dallas and I remember how fast people drive in Texas!
 
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Jerry Bransford said:
What you would notice on the road with 4.11 gears and your 42RLE is your TJ's performance would be absolutely TERRIBLE... no power and the engine would lug badly on the highway when in Overdrive. It would actually still lug even with the Overdrive shut off.
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The part in red is absolutely wrong. It is the opposite. Overall ratio with 5.38 R&P and .69 OD is 3.71. Mathematically, RPM at 70 is 2495 with 35s. Overall ratio with 4.10 R&P and 1:1 trans gear is 4.10. Mathematically, RPM at 70 is 2755 with 35s.

With a 4:1 T-case, I would happy with a 32RH and 4.10 gears on 35s. I basically drove my Rubicon like that for a year by NEVER using OD. I am not thrilled with the 4:1 and 5.38 gears with a torque converter, too low IMO. With a 2.72 T-case I would want more axle ratio to get better crawl ratio. An OD trans with deep axle gears would be help if running a 231 T-case.
 
Joemac said:
Ryan,
I need some first-hand advice. What did you decide to do with your rig? I plan on similar use as you (but I’m in Texas) mainly flat land, road driving, some highway (60-70mph), maybe a summer trip to TX hill country, Colorado mountain trails. I have a 2006 LJ (non Rubi) w/ 42RLE, Dana 30/44, running 315/70-17’s (34.5”). I took advice of websites & axle shop & regeared to 4.56; its terrible & $2k wasted.
What did you go with? 35’s & 5.13’s? How does she do on road? How are RPM’s? Is it too low/loose starting on wet/slick pavement? (Don’t want it squirrelly if my kid is driving). How is it off-road in low gears? ANY advice greatly appreciated.
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I'm just up the road in Montgomery. Let me know if you decide to remove your 4.56 gears. I have an LJ too but it is getting a v8 and a transmission with a lot wider ratios so those gears may be perfect for me.
 
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My LJ is not a rubicon, so have the 44/30 combination, also running 35 inch tires with 5.13 gears, wish I could have gone with 5.38.
When not in my wheeling season I switch to a set of 33" tires and the difference in performance is amazing. (have two full sets of tires and rims) Go with the 5.13, do not let your shop convince you of anything else.
 
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CaliSteve said:
My LJ is not a rubicon, so have the 44/30 combination, also running 35 inch tires with 5.13 gears, wish I could have gone with 5.38.
When not in my wheeling season I switch to a set of 33" tires and the difference in performance is amazing. (have two full sets of tires and rims) Go with the 5.13, do not let your shop convince you of anything else.
Click to expand...
deleted due to wrong reply
 
If that shop had said, go 4.88 if it's your DD than I could say that maybe they were trying to think it through... Sadly though, without using the proper data. But 4.10's? No way. As EVERYONE has said, that's a horrible choice and clearly from a completely uninformed shop.
 
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