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post #1 of 11 Old 03-10-2002, 03:50 PM Thread Starter
TJSahara5703
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Gears

I got my TJ Sahara in may and have put a few engine mods on, but I'm planning on running 33's in the near future, and want to get added power. Everyone seems to say get 4.10 or 4.56 gears as opposed to my stock 3.73's. I gotta be honest I don't really understand the whole concept of what needs to be replaced. Is it the Ring and Pinions? The Gears themselves? or both? Could someone explain it?

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post #2 of 11 Old 03-10-2002, 08:16 PM
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Are you running auto or manual tranny? If you have auto you can keep your 3.73's and you won't have any problems. If you have a manual you should go to 4.10's. Good rule of thumb for gears is .12 X tire size = gears. This applies to a manual tranny. Auto tranny can get away with one size larger tire because of the torque converter. .12 X 33 = 3.96. They don't make 3.96 so you have to go to 4.10. If you have auto then your 3.73 will be fine. It will actually lower your rpm's. I have 31"s wth 3.73's and run 2900 rpm's at 65. 33ws will cut that to about 2600 rpm's. I am going to 33's very soon.

2007, 4 door, powered by a minivan engine, locked and riding on 35's.


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post #3 of 11 Old 03-10-2002, 09:19 PM
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Quote:
Originally posted by TJSahara5703:
I got my TJ Sahara in may and have put a few engine mods on, but I'm planning on running 33's in the near future, and want to get added power. Everyone seems to say get 4.10 or 4.56 gears as opposed to my stock 3.73's. I gotta be honest I don't really understand the whole concept of what needs to be replaced. Is it the Ring and Pinions? The Gears themselves? or both? Could someone explain it?

The ring gear and the pinion gear are matched for each different ratio. You have to replace both the ring gear and the pinion gear in the front and rear axles to change axle ratios. As for what ratio, I would go with 4.10's for 33's with an automatic and 4.56's with a standard.

'86 CJ7, 258 w/Mopar MPI, 4.56 gears, rear Detroit/front Truetrac, full cage, OBA, 8274, 4" lift via Alcans/Rancho, 35's on beadlocks, other stuff. Built for rocks, mud is a four letter word.
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post #4 of 11 Old 03-10-2002, 09:48 PM Thread Starter
TJSahara5703
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So you only have to change the ring and pinion gears in the axles? What about the transmission gears? like 3rd 4th etc.
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post #5 of 11 Old 03-11-2002, 07:29 AM
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just the R&P's. dont have to do anything with the tranny.

'99 XJ RE3.5

past:
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post #6 of 11 Old 03-11-2002, 11:26 AM Thread Starter
TJSahara5703
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Gatorfish you still have your 4.10's? I have a dana 30 front and a dana 44 in the rear.
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post #7 of 11 Old 03-11-2002, 12:02 PM
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yep, I have the ring and pinion for the D30. R&P only. They have 12000 miles.

'99 XJ RE3.5

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post #8 of 11 Old 03-11-2002, 02:29 PM
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Quote:
Originally posted by SamFromCO:

The ring gear and the pinion gear are matched for each different ratio. You have to replace both the ring gear and the pinion gear in the front and rear axles to change axle ratios. As for what ratio, I would go with 4.10's for 33's with an automatic and 4.56's with a standard.
4.56's isn't required with a 4.0. RPM's would be really high on the highway. Over 3000 at 65.

2007, 4 door, powered by a minivan engine, locked and riding on 35's.


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post #9 of 11 Old 03-11-2002, 05:59 PM
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The performance improvement of changing from 3.73 to 4.10 is not enough to justify the cost in my opinion. In your case, I'd just stick with the 3.73s unless you're going to 4.56s. Myself, I ran 4.10s with 33s. Only because I did the gear change when I had 31s. Just couldn't stomach the stock 3.07 ratio. Once I got to the 33s, I wished I had done the 4.56s.

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post #10 of 11 Old 03-12-2002, 09:25 AM
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Quote:
How do you figure? According the the gear calculator on dirtroad.com, 65 mph with 4.56 gears, 0.73 fifth gear, 1 to 1 high range and 33's would put you a 2200 rpm.


I find that to be really low. I run 31's with 3.73's and at 65 I get 2900 rpm's.


To answer TJSahara's question, if you're planning to go with 35's in the future, go with the 4.56s. If you're never going higher than 33s, try out the 3.73s and switch to 4.10s if you need to.[/B]
I agree with the above. Try it out then change to 4.10's. 4.56's only if you plan on going to 35's.

2007, 4 door, powered by a minivan engine, locked and riding on 35's.


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post #11 of 11 Old 03-12-2002, 07:14 PM
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As far as changing your ratio, here's what I did. I have a CJ with a 3spd auto trans no overdrive here. I had an OEM 3.54 ratio and 33's. It did so-so but I wasn't real happy with the ratio. I opted for 4.56's knowing I would be going to 35's as soon as the pocket book allows. Right now I tach about 3400 @ 65-70 mph. This doesn't seem to bad in my opinion, but I don't drive it everyday either. Gear ratio guides tell me that 4.56's and 35's are almost equal to what my stock set up was(back in the day). If I were you I would go 4.10's if you plan on staying at 33's and you primarily drive on road. If you plan on 35's then go all the way to 4.56's(might as well only change gears once) or if you mainly drive off-road then go to 4.56's with the 33's. As far as changing things I think only the R&P need changing you should have the good carrier already since you have stock 3.73's( I know the Dana 30 you have up front changes at 3.73)

Good luck and happy wheeling
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