Axle gearing: 4.56, 4.88, or 5.13?

[Longhorn84]

I have a 5.3L LS (stock), 4l60e (stock), and current rear is 4.56 that the previous owner did. After reviewing his receipts from a million years ago, I'm not sure if they actually did the front regear, I've only used 4H once in the sand for a few circles. Non-rubicon so Dana 30/Dana 35 set up. This is a fun weekend pavement princess that my kids enjoy, I don't off-road currently.

As my other post eluded to, I'm chasing acceleration / pep with the LS swap and considering a higher stall torque converter (need to fix a rear main seal leak anyway). My Dana 30 needs brake upgrades and new ujoints, probably bearings while I'm in there. So, I'm considering going to a currie 44 front for now and eventually probably a currie 60 in the rear to get disc brakes and the HP as I hope one day my kids drive this rig and want it to be beefed up, reliable, and easier to maintain (and/or more sellable). Currie caster / pinion angles would help with on road manners as an added bonus. So, the dilemma is, 4.56 vs 4.88 vs 5.13 gears, Currie recommends 4.56 or 4.88 for me.

Again, I don't necessarily care about highway RPMs or gas mileage, but want pep, seems like 4.88s are the way to go, or would 5.13s be ideal? However, I'm not sure of the "value" of going from 4.56 to 4.88 in terms of real world off the line performance. Most posters on here are thinking about highway rpms (I have the overdrive .70 in 4th) or off-road performance, but I'm wondering if the acceleration is worth the investment. I couldn't justify re-gearing 4.56 to 4.88 solely for the performance but as I mentioned, there are many other benefits of the new axles. Much cheaper route is obviously just do the u-joints, bearings, and do a black magic upgrade and call it a day but what's the fun in that?

If I go the expensive route, I'm ok with the investment and the learning process as I do all the work myself (and I can make a few YT videos to help others). I do like the plug and play currie vs used axles that I'd have to work on / re-gear / re-work brackets / etc.

What would you do if you were me?

 

[bbaldwin237]

I wouldn't invest money into the 30/35 with an LS swap personally. I'd be putting the money aside to save for a swap.

 

[Longhorn84]

I wouldn't invest money into the 30/35 with an LS swap personally. I'd be putting the money aside to save for a swap.

I'm on board with that, then my question is if I'm spending all that dough I want to get the gears right, hard to make the "right" decision with so many variables. I'm leaning 4.88 but I can't help but wonder how much acceleration I'd get with 5.13s.

 

[Wildman]

I'm on board with that, then my question is if I'm spending all that dough I want to get the gears right, hard to make the "right" decision with so many variables. I'm leaning 4.88 but I can't help but wonder how much acceleration I'd get with 5.13s.

For a little perspective I have 5.13 gears in my axles. If you're seriously considering an axle swap (Rear) then I'd start watching marketplace & other online sales sights for a pair of axles with either 4.88 or 5.13 gears in them. You'll probably end up spending less buying them already setup how you want than to buy a new rear axle & then have them both regeared or if the rear came with the gearing you want the front.
Not a real acceleration video but it's one of the few I have when I was still running 35" tires.

If it was me I'd do axles first with 5.13 gears and then if it's still not as peppy as you're hoping for then start looking for a different torque converter.

 

[Longhorn84]

For a little perspective I have 5.13 gears in my axles. If you're seriously considering an axle swap (Rear) then I'd start watching marketplace & other online sales sights for a pair of axles with either 4.88 or 5.13 gears in them. You'll probably end up spending less buying them already setup how you want than to buy a new rear axle & then have them both regeared or if the rear came with the gearing you want the front.
Not a real acceleration video but it's one of the few I have when I was still running 35" tires.

If it was me I'd do axles first with 5.13 gears and then if it's still not as peppy as you're hoping for then start looking for a different torque converter.

Maybe a more specific question is other than a quicker shift out of first and higher rpm on the highway, what are the other downsides of going to 5.13s on 35s?

 

[Wildman]

4.88 on the right & 5.13 on the left. I set your tire size @ 34.25" since they aren't never actual size.

And here's your crawl ratios... Which I understand is as big a deal for you but thought I'd show.

https://www.grimmjeeper.com/gears.html

 

[Rickyd]

Maybe a more specific question is other than a quicker shift out of first and higher rpm on the highway, what are the other downsides of going to 5.13s on 35s?

Higher potential for incurable driveshaft vibrations.

 

[Wildman]

Higher potential for incurable driveshaft vibrations.

Have you heard of this with other transmissions than the 42RLE?

 

[Longhorn84]

Higher potential for incurable driveshaft vibrations.

I haven’t heard that, appreciate the note! I’m feeling like 4.88 are going to be good. I am planning a higher stall TC and I obviously don’t want to spin the tires from a dead stop.

 

[Wildman]

I haven’t heard that, appreciate the note! I’m feeling like 4.88 are going to be good. I am planning a higher stall TC and I obviously don’t want to spin the tires from a dead stop.

Play with the GrimmJeep website and see what different ratios do for you.

If you look at driveline vibrations you'll find it talked about on here. I don't have the talked about vibrations with mine but I do get a shudder now & then at lower speeds that I haven't figured out yet.

 

[Abendage]

If you aren’t off-roading I don’t see much point in upgrading the front. Throw some Black Magic Brakes on it, verify that it was or wasn’t regeared to 4.56. If it was, I’d upgrade the rear axle and match to 4.56 and spend the 6k you were going to spend on the front axle to motor goodies if you’re after performance. For that kind of money find another block and send it to a local engine builder and have them work their magic. The rear axle could be a pretty inexpensive upgrade too, a TJ 44, ford 8.8, etc. if you aren’t off-roading no sense in dropping 10k+ on axles.

 

[Longhorn84]

If you aren’t off-roading I don’t see much point in upgrading the front. Throw some Black Magic Brakes on it, verify that it was or wasn’t regeared to 4.56. If it was, I’d upgrade the rear axle and match to 4.56 and spend the 6k you were going to spend on the front axle to motor goodies if you’re after performance. For that kind of money find another block and send it to a local engine builder and have them work their magic. The rear axle could be a pretty inexpensive upgrade too, a TJ 44, ford 8.8, etc. if you aren’t off-roading no sense in dropping 10k+ on axles.

You are not wrong and there is wisdom here. I think it's just ego and also the crazy thinking that if I ever sell it that a clean LS swap with Dana 44/Dana 60 would give me a better chance of moving it or the dream of passing it down to my kids and maybe they wheel it. You should have heard me try to convince my wife to let me katzkin the seats with cooling/heating today, she shares your sentiment of making no sense on spending too much money on the old mall crawler!

If you were me, and front axle gearing didn't matter (pretend I disconnect driveshaft), with the rear would you go 4.56, 4.88 or 5.13?

 

[lBasket]

You are not wrong and there is wisdom here. I think it's just ego and also the crazy thinking that if I ever sell it that a clean LS swap with Dana 44/Dana 60 would give me a better chance of moving it or the dream of passing it down to my kids and maybe they wheel it. You should have heard me try to convince my wife to let me katzkin the seats with cooling/heating today, she shares your sentiment of making no sense on spending too much money on the old mall crawler!

If you were me, and front axle gearing didn't matter (pretend I disconnect driveshaft), with the rear would you go 4.56, 4.88 or 5.13?

You never get the money you put into a vehicle back when you sell it, so don't put an expensive axle you don't need purely for the next guy

 

[Abendage]

You are not wrong and there is wisdom here. I think it's just ego and also the crazy thinking that if I ever sell it that a clean LS swap with Dana 44/Dana 60 would give me a better chance of moving it or the dream of passing it down to my kids and maybe they wheel it. You should have heard me try to convince my wife to let me katzkin the seats with cooling/heating today, she shares your sentiment of making no sense on spending too much money on the old mall crawler!

If you were me, and front axle gearing didn't matter (pretend I disconnect driveshaft), with the rear would you go 4.56, 4.88 or 5.13?

Resale is a fallacy, you’ll get 20 cents on the dollar back, if that, on your investment.

I’d go with the lowest numeric gear possible. The higher you go the weaker they get.

 

[MBDIAGMAN]

Have you heard of this with other transmissions than the 42RLE?

I don’t think he has the transmission model in mind with his statement about driveshaft vibration. It has to do with driveshaft speed. The lower the gear(higher numerically). Comes with faster driveshaft rotation which makes vibration more likely and balance/condition more important and critical.

 

[Rickyd]

Have you heard of this with other transmissions than the 42RLE?

Don't the chebby autos also have a high overdrive?

 

[Longhorn84]

Resale is a fallacy, you’ll get 20 cents on the dollar back, if that, on your investment.

I’d go with the lowest numeric gear possible. The higher you go the weaker they get.

Definitely agree with you, I'm thinking if I re-gear it will be 4.88s.

 

[Wildman]

I don’t think he has the transmission model in mind with his statement about driveshaft vibration. It has to do with driveshaft speed. The lower the gear(higher numerically). Comes with faster driveshaft rotation which makes vibration more likely and balance/condition more important and critical.

While I agree with this to a point then why doesn't the AX15/NV3550 have the same vibrations when regeared to 5.13 or 5.38? It's only with the 42RLE that this seems to happen and not on all of them. Now I'll say I've been running more aggressive rubber so if I had driveline vibrations I might not know it & I don't normally drive mine @ 70 MPH or more but I don't have the vibrations I read about & I've got 5.13 gears.

Don't the chebby autos also have a high overdrive?

0.70

Definitely agree with you, I'm thinking if I re-gear it will be 4.88s.

I'd guess you might be happier with them. Back to your rear axle. Don't know what a Dana 44 goes for in your neck of the woods but if you can't weld/fabricate on yourself then doing a 8.8 might not be worth it. Might look at ECGS for a 489 rear with the gears you want. Then you'll only need to do the front axle.
You could do a TruTrac for a limited slip since it's not a serious off-road rig in the rear.

 

[Longhorn84]

While I agree with this to a point then why doesn't the AX15/NV3550 have the same vibrations when regeared to 5.13 or 5.38? It's only with the 42RLE that this seems to happen and not on all of them. Now I'll say I've been running more aggressive rubber so if I had driveline vibrations I might not know it & I don't normally drive mine @ 70 MPH or more but I don't have the vibrations I read about & I've got 5.13 gears.



0.70



I'd guess you might be happier with them. Back to your rear axle. Don't know what a Dana 44 goes for in your neck of the woods but if you can't weld/fabricate on yourself then doing a 8.8 might not be worth it. Might look at ECGS for a 489 rear with the gears you want. Then you'll only need to do the front axle.
You could do a TruTrac for a limited slip since it's not a serious off-road rig in the rear.

I had looked into ECGS in the past but when I recently priced them out vs a Currie front 44, the price was very similar and for whatever reason I’d choose Currie. Didn’t price the rear and admittedly don’t need the Currie Dana 60 but for the disc brake set up and the beefier yoke I was tempted to go that route. I don’t want to mess with the welding/fabricating and prefer to pay up for “bolt in” although I know it will still take time/effort to install any new axle. I was originally concentrating on the front since I need to do ujoints and brakes and was contemplating a big brake upgrade and thought since I was down there I may as well knock out the front axle.

On the trutrac, does it perform worse on normal daily driving than an unlocked but lockable diff? I was contemplating fitting up a new front axle with an ARB for future but not connecting the air lines for now vs the trutrac but could use some knowledge from folks on that.

 

[Wildman]

I had looked into ECGS in the past but when I recently priced them out vs a Currie front 44, the price was very similar and for whatever reason I’d choose Currie. Didn’t price the rear and admittedly don’t need the Currie Dana 60 but for the disc brake set up and the beefier yoke I was tempted to go that route. I don’t want to mess with the welding/fabricating and prefer to pay up for “bolt in” although I know it will still take time/effort to install any new axle. I was originally concentrating on the front since I need to do ujoints and brakes and was contemplating a big brake upgrade and thought since I was down there I may as well knock out the front axle.

On the trutrac, does it perform worse on normal daily driving than an unlocked but lockable diff? I was contemplating fitting up a new front axle with an ARB for future but not connecting the air lines for now vs the trutrac but could use some knowledge from folks on that.

The 489 uses the JK larger R&P so you're gaining that added strength which was why I'd brought it up for a rear axle. The TruTrac is just a gear driven limited slip so you aren't wearing out the clutch pack like in a normal limited slip. So on the road you won't notice it but when it's wet out it'll help with the traction. It's just a thought.

I'd do a big brake kit on the front & maybe cromo shafts but other than that since you're not wheeling it hard/hardly I'd leave it open.