Gear Ratio Debate

Matthias13

Matthias13

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Northern Arizona
I realize this has been covered extensively, but I've got an an LJ (non-rubicon) with the lovely 42RLE on 35s. When I went to 35s, I had a very reputable shop install 4.56s (knowing I was going to 35s). At the time, I knew hardly anything about the subject, but after more research and reading, this ratio seems very low for the 42RLE on 35s. OD is pretty much useless, and while I haven't tested it thoroughly, Im not sure it will maintain 75 on a flat stretch of highway with OD on in 4th gear. The jeep is basically undriveable on highway trips longer than a few miles, especially in the mountainous area I live in.

The shop owner cites strength as the main reason, as the teeth get smaller as you increase the ratio (?). In fact, he won't install 5.13s on a Dana 30 and says the deepest he will go is 4.88. Having done a lot of reading, I've never seen this issue come up...

Has anyone ever shredded their diff because their gear ratio was too high? Anyone got any insight/advice?
 
Many folks here run 5.38 on their rubicons with no issues. The lowest your Dana 30 will accept is 5.13 but honestly 5.38 or even lower would be ideal for 35s and the auto. Just turn OD off on the highway for now, the 4.0 can handle the revs just fine. In fact, it likes them.

Sounds like the installer is just making excuses on the chance he does a shoddy install. Time to find a new shop.
 
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No doubt, the 0.69 OD ratio is the worst part of the 42RLE. As Jamison says, turn the OD off for an immediate solution. I had the same issue with 33s and 3.07s, 5th gear was useless. I only used 5th in 4LO.

While it may be true the teeth get smaller as the tooth count goes up..... the deeper gear also relieves stress on those teeth.
 
4.56 is better for 33's. My LJ had 4.56 with 35's when I bought it. Not terrible, but not ideal. Less noticeable with a manual though.

4.88, 5.13 = 35's

5.13, 5.38 = 37's
 
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Lol. I have a 2003 TJ on 33 inch tires. I have a Dana 44 and a HP30. The transmission is a 42RLE. I am sporting 5.13s. Been running them for two years now. Find a Jeep mechanic.
 
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I have 5:38's on my 06 TJR with the same motor/tranny. I'd insist on 5:13's if I was in your shoes. My 5:38's really woke up my TJ
 
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steelhd said:
No. I'm running 35s with the auto and 4.88s and it's marginal. Definately not in the recommended range.
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Many look at the lame charts out there and say that 4.88 is 'right'. 5.13 is definitely better and the lowest you can go with a Dana 30.

I'm running 5.38 with 37's. Lower would be nice, but I have a Dana 44 up front/Dana 60 rear. Don't think you can go lower in a Dana 44. Definitely worse with the auto trans.
 
suicideking said:
Many look at the lame charts out there and say that 4.88 is 'right'. 5.13 is definitely better and the lowest you can go with a Dana 30.

I'm running 5.38 with 37's. Lower would be nice, but I have a Dana 44 up front/Dana 60 rear. Don't think you can go lower in a Dana 44. Definitely worse with the auto trans.
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Doesn't matter, you have the lowest you can go in HP axles which you have front and rear.
 
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Matthias13 said:
I realize this has been covered extensively, but I've got an an LJ (non-rubicon) with the lovely 42RLE on 35s. When I went to 35s, I had a very reputable shop install 4.56s (knowing I was going to 35s). At the time, I knew hardly anything about the subject, but after more research and reading, this ratio seems very low for the 42RLE on 35s. OD is pretty much useless, and while I haven't tested it thoroughly, Im not sure it will maintain 75 on a flat stretch of highway with OD on in 4th gear. The jeep is basically undriveable on highway trips longer than a few miles, especially in the mountainous area I live in.

The shop owner cites strength as the main reason, as the teeth get smaller as you increase the ratio (?). In fact, he won't install 5.13s on a Dana 30 and says the deepest he will go is 4.88. Having done a lot of reading, I've never seen this issue come up...

Has anyone ever shredded their diff because their gear ratio was too high? Anyone got any insight/advice?
Click to expand...
Here is a point you can try and make with your gear guy. May not help immediately, but at some point it may sink in and he won't remain as ignorant.

As stated, as the gear ratio gets higher numerically, for the same work performed, the stress is actually less on the gear set. That isn't the point though, tell your gearhead to go check all the sites that sell the 5.13's and 5.38's. Look at the warranty and note they all have one.

If the gear sets in that ratio were an issue, you would see something to the effect of - These are limited warranty parts, they are problematic and should only be used by those who are okay with swapping them out frequently due to the nature of this low ratio being weak and prone to breakage. Use at your own risk!

Once that sinks in for a second, they may realize that no gear company that we use would ever write that and instead they just wouldn't sell the damn things. They don't need the hassle or bad reputation from the idiots who would install them and demand a warranty when they fail.

You may also point out that way back when the first sets of 4.88's popped up, the same shit was said. OMG, don't run those, the pinion is soo small that it will break if you look at it sideways. Run 4.56's instead. Now they are holding up the 4.88's as the gold standard of strength. Funny how that works.
 
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I've been looking at 5.13 gears also. I noticed that East Coast Gear Supply does not warranty 5.13s in their HP Dana 30. :unsure:
 
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suicideking said:
I wouldn't buy from them then.
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Thanks for the advice. I hadn't heard of them before. I was just bored enough to be looking around on Google and ended up at their website. I though it was curious that they specifically stated they don't warranty the 5.13's.
 
06lj said:
Thanks for the advice. I hadn't heard of them before. I was just bored enough to be looking around on Google and ended up at their website. I though it was curious that they specifically stated they don't warranty the 5.13's.
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Because they're too inexperienced/ignorant/stupid to know just how popular and how well 5.13 gears work in the Dana 30.
 
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I've asked if he will just put in 5.13s and if I blow the diff I'll eat my words. Sucks because he's offering a significant discount to regear since I wasn't happy with 4.56s. So if I go elsewhere I'm paying at least double.

Edit: He'll put 5.13s in lol. Let's hope this is worth the headache! 4.56s suck.
 
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