Re-gear question: 3.07 to ?

1999tj

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Hello,

First time post, been lurking for a month or so. Hoping the crew here can help.

Late September, I bought a 1999 TJ with the 4.0 engine, manual transmission. It has been a blast so far, and will be my daily driver for a least the nest few years. It will see occasional off road use (hunting camp trails, etc), but no major mud or rock crawling expected. Its destined for pavement & gravel roads for now, but i like having the "down & dirty" option when needed. The axle setup is Dana 30 fromt, Dana 35 rear. I'm running 33" tires, and discovered on a road trip that 5th gear is pretty useless if I want to maintain speed up hills, in a headwind, etc. I've read about doing a gear swap, and am trying to put together an order for the upgrade. Here is where I have questions...

I've decided to go with Revolution for the Dana 30/Dana 35 ring and pinion master install kit (thanks Chris and fellow members for sharing your review and opinions!). I know I'll also need front & Rear carriers, too. Will I need just the empty carriers, or the version that comes with spider gears, too? Also, do you recommend that I go with 4.10 or 4.56 based on my intended usage/needs? Again, I'm not a rock crawler but want a capable vehicle for daily pavement/highway, and 4-5 weekends a year in the woods chasing Bambi or hogs.

Thanks in advance for the help, and I hope to one day have some knowledge to share here as well.
 
4.56 is the generally accepted best all-around ratio for 33's, 4.0L engine and 5-speed manual transmission. 4.56 will give you ideal RPMs on the highway, and great off-road performance as well. Just make sure to not let anyone talk you into also installing a locker into your rear Dana 35 which in stock form is not strong enough for a locker.

My other suggestion is to have the installing shop provide ALL of the parts. That way if there's any problem during or after installation there will be no issues with the shop taking care of them under warranty. If you gave them the parts that would give them the perfect opportunity to blame your parts and then you're stuck with getting whatever went bad/was damaged replaced by who you bought the parts from. And usually problems are caused by improper installation technique I wouldn't give the shop/installer any way out of having to take care of any possible future problems. And trust me, even experienced gear installers don't always get the gears set up perfectly as is required.
 
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4.56 is the generally accepted best all-around ratio for 33's, 4.0L engine and 5-speed manual transmission. 4.56 will give you ideal RPMs on the highway, and great off-road performance as well. Just make sure to not let anyone talk you into also installing a locker into your rear Dana 35 which in stock form is not strong enough for a locker.

My other suggestion is to have the installing shop provide ALL of the parts. That way if there's any problem during or after installation there will be no issues with the shop taking care of them under warranty. If you gave them the parts that would give them the perfect opportunity to blame your parts and then you're stuck with getting whatever went bad/was damaged replaced by who you bought the parts from. And usually problems are caused by improper installation technique I wouldn't give the shop/installer any way out of having to take care of any possible future problems. And trust me, even experienced gear installers don't always get the gears set up perfectly as is required.
When you said not to install a locker do you think posi would be ok for D-35
 
I just went through same deal as you. Lurked and read for a while before changing gears. I decided on 4.10 from 3.07 and I’m very happy with end result. One guy in one of my posts said it was like Forest Gump running with his braces on and after they fell off he was able to take off. Perfect analogy!
If it’s a daily driver and some off road the 4.10 is perfect.
Good luck!


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Thanks for the replies & advice, guys. Sounds like 4.56 is the way to go!

Can anybody clarify my question regarding front & rear carriers? I'm going to let my installer source the parts (again, great advice there), but I want to have at least a casual knowledge of what is being done to the vehicle & why. I plan on maintaining the Jeep myself based on my capabilities, and growing my mechanical knowledge would be a plus.

Thanks again!
 
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If it’s a daily driver and some off road the 4.10 is perfect.
I wish I could agree with that. I ran with 4.10 gearing with 33" tires/4.0L engine/5-speed transmission and the rpms were slightly too low.... I had to downshift with even minor grades. Being slightly undergeared like that was extremely frustrating for me. Trust me, not that 4.56 would be slightly overgeared, it's far better to be slightly overgeared than slightly undergeared like 4.10 is for 33" tires.
 
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I wish I could agree with that. I ran with 4.10 gearing with 33" tires/4.0L engine/5-speed transmission and the rpms were slightly too low.... I had to downshift with even minor grades. Being slightly undergeared like that was extremely frustrating for me. Trust me, not that 4.56 would be slightly overgeared, it's far better to be slightly overgeared than slightly undergeared like 4.10 is for 33" tires.

Interesting. I believe you but not same experience I’m having. Things that make you go hmmmm! [emoji41]


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Interesting. I believe you but not same experience I’m having. Things that make you go hmmmm! [emoji41]
Driving when slightly undergeared will often seem fine until you drive a Jeep with the same configuration but with a more appropriate axle ratio. I knew I was slightly undergeared with 4.10 and 33's within a day or two after having the gears installed (all my buddies recommended 4.56) but driving another TJ regeared to 4.56 with 33" tires made me slap my forehead afterward. I hated driving after that, every extra downshift I had to do for even a minor grade grated on me. I vowed to never be slightly undergeared again when I'm deciding on the ratio to be installed. :)
 
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Thanks for the replies & advice, guys. Sounds like 4.56 is the way to go!

Can anybody clarify my question regarding front & rear carriers? I'm going to let my installer source the parts (again, great advice there), but I want to have at least a casual knowledge of what is being done to the vehicle & why. I plan on maintaining the Jeep myself based on my capabilities, and growing my mechanical knowledge would be a plus.

Thanks again!
Yes, both carriers need to be changed. So now is the time to add in a Truetrac in the rear, maybe in front too depending on your planned usage. A locker in the 35 is a no go unless you go with a Super 35 kit, which is 30 spline alloy axles and a locker in some configuration. The reason for needing new carriers is, the lower the ratio (higher numerically) the smaller the pinion gear gets so the ring gear has to move closer. The lower ratio carrier moves the ring gear seat closer to close that gap. There are also "thick" ring gears that do the same by, as it states, making that gear thicker. Either one works fine but, there aren't thick gear sets for every differential.
 
How do you feel about those 33's? Think you ever want to go bigger? Maybe scale back and go smaller? I pose this question because once you choose a ratio, you are pretty much stuck with the tire choice to match the gearing. I re-geared to 4.56's and am running 33's. It's perfect, but I have contemplated bumping back to 31's, but now I'm stuck. Had I went with 4.10's I would have had the option. 4.10's wouldn't have been ideal for 33's, but it would have been doable for my needs. Just something to think about.
 
Odd man out here but I have a TJR, 4.10s, 33s. Wish I had 3.73s. I've owned a standard all my life and several of them were 18speeds. Dropping a gear is a fact of life.

The real issue with gearing, especially with 35s and up is lift in first gear. Or lift off road in 1st gear, LO Range. If you are geared low enough the climb that rock in 1st, 4LO, yer done.

5th or 6th, the overdrive gears were never intended to provide peak power for passing or climbing mountain grades. OD was intended to drop the rpms for a quieter, more efficient highway cruise. That said if highway mileage is of no interest to you. If you'd rather not ever shift, yeah go for the 4.56/4.88 or.....

The best performance cars out there like say the A8..... reach top speeds of 150mph down 2 or 3 gears. Like 5th in an 8speed automatic. The other 3 gears are designed to improve comfort, economy, emissions. And OD gears are actually weaker than the direct gear of 5th in a 6 speed or 4th in our 5 speeds. So if you need to drop a gear for a grade?? Good because that is how Jeep designed your ride.

Me, when I tow trailer in the mountains, I never use 6th gear towing and often climb the 3 lanes in 4th or 3rd. Not an issue, I'm not scared of using that clutch.
 
Odd man out here but I have a TJR, 4.10s, 33s. Wish I had 3.73s. I've owned a standard all my life and several of them were 18speeds. Dropping a gear is a fact of life.

The real issue with gearing, especially with 35s and up is lift in first gear. Or lift off road in 1st gear, LO Range. If you are geared low enough the climb that rock in 1st, 4LO, yer done.

5th or 6th, the overdrive gears were never intended to provide peak power for passing or climbing mountain grades. OD was intended to drop the rpms for a quieter, more efficient highway cruise. That said if highway mileage is of no interest to you. If you'd rather not ever shift, yeah go for the 4.56/4.88 or.....

The best performance cars out there like say the A8..... reach top speeds of 150mph down 2 or 3 gears. Like 5th in an 8speed automatic. The other 3 gears are designed to improve comfort, economy, emissions. And OD gears are actually weaker than the direct gear of 5th in a 6 speed or 4th in our 5 speeds. So if you need to drop a gear for a grade?? Good because that is how Jeep designed your ride.

Me, when I tow trailer in the mountains, I never use 6th gear towing and often climb the 3 lanes in 4th or 3rd. Not an issue, I'm not scared of using that clutch.
Your 6 speed is not comparable in any gearing discussion to any of the 5 speed manual transmissions. If you swapped a 5 speed in, you would not want 3.73's.
 
I am like the OP... dailey driver, 4.0 on 33.s only dif is a automatic. I just did the swap from 3.73 to 4.56 and I am very pleased.. gearing is spot on...

Hey. Glad to hear you are enjoying them. Scott said you were contemplating the Super 35. If so, let me know. I still have some of the Superior TJ Dana 35 trusses as well.
 
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