Do I need the master overhaul kit when re-gearing

[D M]

Hey all,
I'm gonna go with 4:88s down the road for my current 33s, so I can make the jump to 35s in the future because 373s, nv3550 with 33s SUCKS. Don't let anyone fool you otherwise. I plan to go with revolution gears 4:88, and can someone tell me if I need the master overhaul kit with bearings and all that? Id like to have all the parts in hand and bring it to a shop to install. Also ive heard talk of "thick cut" gears or something like that, which is a set that doesnt need to be broken in? I have heard that they tend to be weaker, correct me if im wrong. If someone would also post links as to where to get them id appreciate it.

 

[Steel City 06]

Thick cut gears are gears that are intended for use with a carrier designed for taller gear ratios.

For example, factory Dana 44 carriers typically come in the 3.73 and down ratio. If you wanted 4.10 or higher, you would have to replace the carrier, as the spacing is incorrect.

But thick cut gears are designed to fill that space so you don't have to replace the spacer. Rubicon 4.10 gears are actually thick cut gears.

 

[D M]

Thick cut gears are gears that are intended for use with a carrier designed for taller gear ratios.

For example, factory Dana 44 carriers typically come in the 3.73 and down ratio. If you wanted 4.10 or higher, you would have to replace the carrier, as the spacing is incorrect.

But thick cut gears are designed to fill that space so you don't have to replace the spacer. Rubicon 4.10 gears are actually thick cut gears.

So the thick cut gears actually replace the whole carrier? And what about the certain type that doesnt need to be broken in?

 

[Steel City 06]

So the thick cut gears actually replace the whole carrier? And what about the certain type that doesnt need to be broken in?

No, they allow you to reuse factory carriers in certain situations. There is no advantage or disadvantage to thick cut gears other that only thick or only standard cut gears will fit a particular carrier.

As the gear ratio gets deeper, the pinion gets smaller in diameter. To compensate, as gears get deeper in ratio, the ring gears are made thicker to move the teeth closer to the pinion. At a certain point, the gears get excessively thick, and to save money, OEMs will use a different carrier that mounts the ring gear closer to the pinion so that an excessive amount of metal isn't required.

On an economy of scale building thousands of axles, the cost savings from the carrier break save the manufacturer money. But for the average aftermarket buyer, they probably already have a carrier, and thick cut gears may be the economical option if the buyer wants to keep a factory carrier.

What axles do you have, and what gear ratio do you currently have? Do you plan to add lockers or other new carriers? That will likely tell you if thick cut gears are needed.


The gears that don't require break in you are referring to are probably REM-surfaced gears. This is a service that takes the gears and polishes them to a mirror like finish to remove surface irregularities. This can be done on any gear set of any brand, though Revolution directly offers it as a service on their products.

 

[D M]

No, they allow you to reuse factory carriers in certain situations. There is no advantage or disadvantage to thick cut gears other that only thick or only standard cut gears will fit a particular carrier.

As the gear ratio gets deeper, the pinion gets smaller in diameter. To compensate, as gears get deeper in ratio, the ring gears are made thicker to move the teeth closer to the pinion. At a certain point, the gears get excessively thick, and to save money, OEMs will use a different carrier that mounts the ring gear closer to the pinion so that an excessive amount of metal isn't required.

On an economy of scale building thousands of axles, the cost savings from the carrier break save the manufacturer money. But for the average aftermarket buyer, they probably already have a carrier, and thick cut gears may be the economical option if the buyer wants to keep a factory carrier.

What axles do you have, and what gear ratio do you currently have? Do you plan to add lockers or other new carriers? That will likely tell you if thick cut gears are needed.


The gears that don't require break in you are referring to are probably REM-surfaced gears. This is a service that takes the gears and polishes them to a mirror like finish to remove surface irregularities. This can be done on any gear set of any brand, though Revolution directly offers it as a service on their products.

I currently have 3:73s, with my dana 30/44 combo. I plan on doing a rear ARB or Eaton E-Locker down the road on top off 4:88s

 

[Steel City 06]

I currently have 3:73s, with my dana 30/44 combo. I plan on doing a rear ARB or Eaton E-Locker down the road on top off 4:88s

Assuming those are factory gears and carriers, you can use standard cut gears on your front factory carrier (the carrier break is 3.55/3.73), and you can use thick cut gears on your factory rear carrier.

If you do buy the thick cut gears for the factory carrier and plan to reuse them with a locker in the future, you'll need a locker for 3.73 and down, not 4.10 and up.

If you're willing to do the locker at the same time as the gears (saves a lot of labor cost), simply buy standard cut gears and a carrier for 4.10 and up. This is the route I recommend.

 

[Daryl]

If you’re planning on running 35’s, you may want to rethink your gear ratio choice.

 

[Steel City 06]

If you’re planning on running 35’s, you may want to rethink your gear ratio choice.

Personally, I would go 5.13 with the 5 speed and 35s.

I have 35s and plan to go to 4.88, but the 6 speed I have doesn't have as tall an overdrive as the 5 speeds.

 

[cpwolf]

I have 35s and plan to go to 4.88, but the 6 speed I have doesn't have as tall an overdrive as the 5 speeds.

What do you have now with your 6 speed, 3.73 or something different?

 

[D M]

If you’re planning on running 35’s, you may want to rethink your gear ratio choice.

5:13 is going to be too high rpm for my driving with 35s.

 

[Daryl]

5:13 is going to be too high rpm for my driving with 35s.

No it won’t.

 

[Steel City 06]

What do you have now with your 6 speed, 3.73 or something different?

4.10.
It works out so that 5th (1:1) gear with 4.10 is exactly the same final drive ratio as 4.88 and 6th (4.88×0.84=4.10×1.00). So currently I use 5th gear instead of 6th on the freeway, and it is perfectly placed.

4.88 would not only give an appropriate amount of torque in 6th for cruising at freeway speeds, it also puts 4th gear in the power band at around 4500 RPM at 70-75 mph.


For a 5 speed, the equivalent of that would be 5.13. You would lose the ability to use 3rd gear at freeway speeds, but 4th is close enough to the power band you wouldn't need 3rd.

Most manual owners target 3000 RPM at 75 mph, which translates to 5.13 on a 5 speed and 35s.

 

[Chris]

Take it from someone who has the NV3550, 35s, and 4.88 gears... it still sucks!

 

[cpwolf]

Take it from someone who has the NV3550, 35s, and 4.88 gears... it still sucks!

I hear you, I have 4.11 gears and 6 speed, just curious how bad of a dog it is on 35’s, if I can put the regear off and go ahead and get 35’s and suck it up, ha. I think 4.88 with the 6 speed is what everyone has said, and I will go Super 35, E Locker and 4.88 all at once. Gonna hurt, ha

 

[Chris]

I hear you, I have 4.11 gears and 6 speed, just curious how bad of a dog it is on 35’s, if I can put the regear off and go ahead and get 35’s and suck it up, ha. I think 4.88 with the 6 speed is what everyone has said, and I will go Super 35, E Locker and 4.88 all at once. Gonna hurt, ha

From stoplight to stoplight it isn't bad. Anything that involves maintain higher speeds though, it sucks big time.

The only solution here is an engine swap, a stroker, or forced induction.

Given the 4.0 only puts down about 156 HP to the wheels on a stock TJ, you can be assured that with 35s, heavy wheels / tires, and all the extra weight, you're probably lucky if you're getting 100 HP at the wheels.

That right there explains quite a bit.

For a weekend warrior or primarily trail driven rig, I see no issue with this. But if you plan to daily drive it, you're going to hate life until that engine is pumping out a lot more power.

 

[Steel City 06]

I hear you, I have 4.11 gears and 6 speed, just curious how bad of a dog it is on 35’s, if I can put the regear off and go ahead and get 35’s and suck it up, ha. I think 4.88 with the 6 speed is what everyone has said, and I will go Super 35, E Locker and 4.88 all at once. Gonna hurt, ha

The 6 speed and 4.10 is actually pretty forgiving with 35s. Definitely not ideal, but if you start from 1st gear most of the time and pretend 6th doesn't exist, it's tolerable on the street and the freeway.

 

[D M]

Most manual owners target 3000 RPM at 75 mph, which translates to 5.13 on a 5 speed and 35s.

Thats a little too high for my liking, how is say 65 mph with 5:13, 35s, and 5 speed

 

[Mudflat]

I’ve only had my TJ a couple of weeks & the 3.07 gears are horrible, especially with the 12.50/33 BFG AT/KO tires. This isn’t even a good mall crawler. This is exactly the way the Jeep was set up when I bought it. Obviously, I am planning to regear soon & keeping the 33s. I’m thinking that 4.10 gears would be about what I need for how I will use the rig; beach, light trail riding & some possible light rocky trails. It will eventually be towed behind a motor home. I suppose I might also have Trac lock or something similar installed at the same time.
All thoughts & suggestions are welcome.

 

[cpwolf]

I’ve only had my TJ a couple of weeks & the 3.07 gears are horrible, especially with the 12.50/33 BFG AT/KO tires. This isn’t even a good mall crawler. This is exactly the way the Jeep was set up when I bought it. Obviously, I am planning to regear soon & keeping the 33s. I’m thinking that 4.10 gears would be about what I need for how I will use the rig; beach, light trail riding & some possible light rocky trails. It will eventually be towed behind a motor home. I suppose I might also have Trac lock or something similar installed at the same time.
All thoughts & suggestions are welcome.

I have an 05 with 6 speed and the 4.0 with 4.11 gears and 33’s. I’ve never felt sluggish or a dog at all. That’s just my experience personally, and I’m going to 35’s in the next year. Your red rig looks awesome, the gear change will be huge.

 

[rasband]

I have an 05 with 6 speed and the 4.0 with 4.11 gears and 33’s. I’ve never felt sluggish or a dog at all. That’s just my experience personally, and I’m going to 35’s in the next year. Your red rig looks awesome, the gear change will be huge.

I run the same in Colorado frequenting the mountains. I have to shift a bit; but it’s definitely workable. It’ll be nice to regear eventually when I do 35s but until then it’s not as miserable on the 4.10s as I read (though that could just be I don’t know what I’m missing).