35s with 4.56 gears

machoheadgames

LED turn signal club
Supporting Member
Joined
Jan 21, 2021
Messages
1,226
Location
Dallas, TX
All that tells you is the 4 speed auto can't be geared low enough for 35s. This is the same justification that I mentioned earlier that led to decades of people not gearing low enough.

Surely you know I realize that, right? I never said the 4 speed auto limitations were ideal either. All I said is that he will end up with a similar setup to what so many of them are already stuck with. Despite how non-ideal that may be, they are still making it down the road.

All I’m saying is his expectations are already low, 4.56 and 35 will be above his low expectations. If you read my post you’ll see where I said 3 times that it’s not ideal and I wouldn’t run it personally. Especially if I didn’t need 35’s. However that doesn’t mean somebody else shouldn’t simply because their gearing isn’t perfectly ideal. The pain of not having enough gearing is only going to affect him anyways, not us.

How about I put this a different way: if 4.56 is so terrible with 35’s in 5th, then why doesn’t he just pretend he has a 32RH and leave it in 4th?
 
Last edited:
  • Like
Reactions: Joe.B

CherokeeKid

Member
Supporting Member
Joined
Nov 27, 2020
Messages
83
Location
Oklahoma
As bad as 3.73 and 33s? I ran that a for months and was ok with it

I ran 2.73's with 33's in a T5 equipped CJ7 for years; now that was awful. Since you're in the ballpark with 4.56's, I'd say try 35's, if you can tolerate it great. If not, re-gear or go back to 33's for next set.
 
  • Like
Reactions: Joe.B

jmo214

Member
Joined
Feb 1, 2021
Messages
26
Location
california
Lower RPMs do not always give better MPG. I seriously doubt your 4.56 is giving better MPG with 35's than a more appropriate 4.88 or 5.13 would with the 5-speed transmission.

The Overdrive ratio in the 42RLE automatic transmission requires significantly lower ratios than the 5-speed does. My present TJ bought used with a 42RLE, 35" tires, and 4.88 gearing got terrible mpg. It never even reached 12 mpg, it was 11-something mpg. Then I regeared it from 4.88 to 5.38 and my mpg shot up to 14.6 mpg.

would u recommend 5.13s on a dana 30 front? i have an auto LJ but the shop near me told me to go 4.56 for 35s. they said not to go 5.13s bc something about pinion angle? i dont wheel my jeep hard bc its my daily driver for now.
 
  • Face Palm
Reactions: JMT

Wildman

Over Analyzer Extraordinaire...............
Staff Member
Supporting Member
Joined
Dec 12, 2015
Messages
24,684
Location
In the hills of WA
would u recommend 5.13s on a dana 30 front? i have an auto LJ but the shop near me told me to go 4.56 for 35s. they said not to go 5.13s bc something about pinion angle? i dont wheel my jeep hard bc its my daily driver for now.

If you search you'll find many recommendations for 5.13's & 35's with the 42RLE. There is no reason not to run these gears in a Dana 30 or Dana 44. The myth of the pinion being too small is bunk and you'll be fine.
 
  • Like
Reactions: jmo214 and tworley

tworley

garagequeen
Supporting Member
Ride of the Month Winner
Joined
May 23, 2018
Messages
7,175
Location
Arvada, CO
would u recommend 5.13s on a dana 30 front? i have an auto LJ but the shop near me told me to go 4.56 for 35s. they said not to go 5.13s bc something about pinion angle? i dont wheel my jeep hard bc its my daily driver for now.

I have been running 5.13s in my Dana 30 for several years now, maybe around 40k miles and it is fine. There was a fear way back when that the pinion with 5.13s was too small
 
  • Like
Reactions: jmo214

JMT

Saxum Erepo 🪨
Supporting Member
Ride of the Month Winner
Joined
Feb 27, 2017
Messages
19,070
Location
🌎
I’m debating on moving up to 35s from 33s I have 4.56 with nv3550, I’m 80% pavement and was wondering if I would be ok running 35s with 4.56?

It depends on what you can tolerate. LIke you, I set up for 33's with NSG-370 and 456 gears. Then I moved to 35's. I'm still on 456 gears. It's not ideal. It's fine 98% of the time. It's only when I'm in the mountains that I have to stay over 70mph or I start dropping speed and gears.

However, there is something else to consider. Vibes. I don't know your current situation and when vibes onset. It may be 90mph, but gearing lower will lower than number. If you're not having trouble now, then re-gearing at 488 won't be a problem. If you are having trouble now, your vibes won't come on till a higher speed, but if you re-gear to 488 they will be essentially the same as they are now. See this post by Tom Wood's on drive shaft speeds.

https://4xshaft.com/blogs/general-tech-info-articles/vibrations-harmonic
 
  • Like
Reactions: FarFire70

Jerry Bransford

TJ Guru Moderator
Staff Member
Supporting Member
Joined
Nov 9, 2015
Messages
25,991
Location
Fleming Island Florida
would u recommend 5.13s on a dana 30 front? i have an auto LJ but the shop near me told me to go 4.56 for 35s. they said not to go 5.13s bc something about pinion angle? i dont wheel my jeep hard bc its my daily driver for now.
That shop is CLUELESS where gearing correctly for your 42RLE automatic transmission is concerned. Your automatic has a .69 Overdrive ratio which drops your cruising rpms much more than other transmissions do. So you need an extra low ratio like 5.13 to get them up where they need to be for 35's. Actually 5.38 is a better choice but your Dana 30 is limited to 5.13. With 5.13 you'll have great highway cruising rpms. If you took that shop's advice and went with 4.56 your engine would be lugging on the highway and your mpg would suffer due to the engine not opera at an efficient rpm. You'll actually get better MPG with 5.13.

When I regeared my present TJ with 35's and the same 42RLE transmission, I went from 4.88 to 5.38 and my highway MPG went up from sub-12 to 14.6.

And their comment on the pinion gear strength not being there for 5.13 (or 5.38 as I run), they're wrong about that too. Low ratio gear sets like 5.13 and 5.38 were re-engineered to bring the pinion gear strength up to be equal to the higher ratios like 3.73, 4.10, 4.56 etc. Most mechanics and shops are unaware of that because they don't stay up on information like that.

Definitely go with 5.13!
 

Grant Lasson

TJ Enthusiast
Supporting Member
Joined
Aug 15, 2019
Messages
281
Location
Sandy, Utah
I went from 5.13 to 4.56. The 5.13s were the PO's choice. Once the ring gear teeth started flying all over the differential, I had to do a re-gear. 4.56 has been fine for my uses. I drive it two days a week to work--40 mile round trip. I live between 4900 and 5200 ft elevation. There are hills. On the freeway, it's perfectly comfortable doing 70 MPH in 4th gear going uphill (3K RPM). 5th gear is useful for flats and downhill. If I could change anything, I would change the gear spacing for 1-4 and especially reverse which I find to be geared much too tall.

I've never been in an off-road situation that 5.13s could do that 4.56 could not (I do have the 4:1 TC so there is that). I suppose it comes down to uses. My primary off-roading is wilderness exploring--not rock crawling. If I really wanted to focus on getting through a nasty rock garden then I'm all in on 5.13s. But I wouldn't 't stop there--I'd want an automatic tx too.