Gear choices

[The Fireman]

So I got a bit of a surprise when I got the axle housings out of my parts jeep, I knew there was rust issues with the jeep when I bought it but didn't expect the spring pads on the rear axles to have holes rusted through them...so my axle swap idea changed into removing the 4.56 gears, and re-gearing my current un-rusted axles that are currently in our 04 TJ.

When I got the front gearset out I got another not so pleasant surprise, it looks like the ring and pinion ran hot at one point causing some discoloration and some galling on the pinion gear. So now I'm looking at buying at least a ring and pinion for the front axle, fortunately the rear looks good.

This however leaves me with a decision to make, I already have master install kits for both front and rear axles so all I need are gears for the front if I reuse the 4.56's from the rear axle. My other option is to replace both the front and rear ring and pinion and re-gear to 4.88's. As of right now we'll be running on 33x12.50 for the foreseeable future but I am going to go with a Savvy 4" lift just incase we do decide to make the jump to 35's someday.

I am trying to build for the future but 35's would be a few years out at best if we ever did go that route, looking at the gear ratio calculator 4.88's would put me at 2750rpm at 70mph and 4.56's are right at 2550. We don't do a whole lot of highway driving but also don't want to be screaming to keep up either when we do have to jump on the interstate . I'm leaning towards the 4.88's so I don't have to revisit this again down the road but I also don't want to regret being over geared either. No matter what it'll be better than the current 3.07's and 31"

Any advice regarding which way to go would be great, thanks.

 

[Jerry Bransford]

What transmission do you have Fireman?

 

[jjvw]

My daily driver is geared for 75mph at 3k rpm. It doesn't scream.

 

[The Fireman]

Sorry bout that I’ve got the 5 speed manual. I knew I was forgetting something

 

[Rob5589]

If you have future aspirations of 35's, yes, 4.88. I would actually lean toward 5.13 personally.

 

[Jerry Bransford]

First, don't be concerned that you'll have "screaming" engine rpms with recommendations made here. At least for myself, all of my recommendations are always and primarily made with ideal highway rpms in mind. And with 35" tires, 2750 is about right which is what I had with my 5-speed. I now only get about 2600 with my 4-speed automatic and 5.38 gears and I'd rather have 2700-2750 at my usual 70 mph cruising speed.

For your 5-speed, I'd go 4.56 for 33's or 4.88 for 35's. If you think you might end up with 35's I'd go 4.88 now. 4.56 is not enough gear for 35" tires.

One last thought when I mention 2600-2750 rpms Don't look at a typical car's tach running small tires where 2100-2200 is normal. Those rpms are not appropriate for a Jeep running significantly bigger tires. The rpms suggested above are right on what you need, don't worry that they're going to be too high for the highway... they're exactly what you need. Not to mention they're be superb when offroad.

 

[Rob5589]

5.13, 34" tire, NV3550 in 5th, at 75 is 2775. Right where you want to be.

 

[Chris]

Don't fall victim to the myth that the 4.0 should be kept under 2000 rpms. That's absolute horsesh*t.

I would go with 5.13 gears for sure.

I run 5.38 on mine, but it's an automatic, hence the deeper gears.

 

[The Fireman]

Thanks for the input, looks like I’ll be ordering some new gears for front and rear axle then. We also tow a small teardrop camper during the summer so 4.88’s would definitely make that more enjoyable than the 3.07’s were.....the mountains in Vermont were no fun at all doing 25-30 mph

I seem to remember reading something here about a manufacturer that now has a ring and pinion that don’t require break in but I can’t recall for the life of me which manufacturer it was. Are there any gear manufacturers I should avoid? my install kits have timken bearings so that part should be good.

 

[Jerry Bransford]

I seem to remember reading something here about a manufacturer that now has a ring and pinion that don’t require break in but I can’t recall for the life of me which manufacturer it was. .

www.revolutiongear.com, that was my writeup on their new process. Since I posted that I've heard from others on that, it's the real deal. I wish it had been available last year when I installed my 5.38 gears, Probably spent 20+ hours making sure they were well broken in before I started towing my trailer on a couple long trips.

You can get the treated RGA gears at a discount from Ricky at www.4lowparts.com, call him & say I sent you please. I owe him a couple favors plus he's a really good guy. Tell him you want RGA's gears with the new REM process which is what eliminates the need for the break-in process. Plus they run quieter and cooler.

 

[The Fireman]

Great thanks jerry, really appreciate it

 

[The Fireman]

Thank you everyone, when I was looking at gears I didn't see 5.13's listed 4.88 was the deepest that I could find on quadratecs site, when I was checking out the link Jerry provided I see they have 5.13's available. When I plug in the NV3550, 33" tires and 5.13 gears I get 2860rpm at 75 with 4.88 its at 2720, might just go the 5.13 route then I would definitely be set for 35...well after brake upgrades and chromoly axles as I'm keeping my Dana 35 and Dana 30. Are there any issues with running 5.13's in those housings? I'm going to use the carriers from my parts axle that has the burnt 4.56's along with the Detroit Truetrac that's in the rear axle

 

[Jerry Bransford]

No problem running 5.13 in those axles. You'll need to install a Super 35 kit with 30 spline shafts into your Dana 35 to run 35" tires.

 

[The Fireman]

Perfect, I figured on the super 35 kit but that upgrade will have to wait until I make the move to 35's at least the gearing will be done and I can wear out the set of 33's that came with my parts jeep before I upgrade any further. If I do upgrade to 35's do they make a kit to change out the gears in the Truetrac to run the 30 spline axles or will I need to replace that and go through setting up my ring and pinion again?

 

[jjvw]

Perfect, I figured on the super 35 kit but that upgrade will have to wait until I make the move to 35's at least the gearing will be done and I can wear out the set of 33's that came with my parts jeep before I upgrade any further. If I do upgrade to 35's do they make a kit to change out the gears in the Truetrac to run the 30 spline axles or will I need to replace that and go through setting up my ring and pinion again?

The gearing will need to be setup with the Super 35 kit. Very few gear guys will want to reuse the existing gears.

 

[tomtaylz]

www.revolutiongear.com, that was my writeup on their new process. Since I posted that I've heard from others on that, it's the real deal. I wish it had been available last year when I installed my 5.38 gears, Probably spent 20+ hours making sure they were well broken in before I started towing my trailer on a couple long trips.

You can get the treated RGA gears at a discount from Ricky at www.4lowparts.com, call him & say I sent you please. I owe him a couple favors plus he's a really good guy. Tell him you want RGA's gears with the new REM process which is what eliminates the need for the break-in process. Plus they run quieter and cooler.

Are the REM ones available currently? When I’m ready in a few weeks I’ll give him a call too @Jerry Bransford

 

[Jerry Bransford]

Are the REM ones available currently? When I’m ready in a few weeks I’ll give him a call too @Jerry Bransford

Pretty sure they are available now Tom, nothing about "coming soon" anywhere.

 

[tomtaylz]

Pretty sure they are available now Tom, nothing about "coming soon" anywhere.

Gotcha I’ll check in. When I reached out to RGA a few weeks ago it sounded like they were still working out the ordering process but might be easier for Ricky

 

[Rob5589]

The TT only comes in 27 spline. Changing the carrier only requires backlash to be readjusted.

 

[The Fireman]

good to know, that will give me an excuse to step up to an ARB air locker in a few years, I'd love to do it all at once but the wallet wouldn't like it so much. At least having bought a parts jeep I'll have a spare set of axle shafts on hand in case anything goes bad but I should be ok on 33's and I'm not one to be to heavy on the skinny pedal