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Discussion Starter · #1 ·
Hello, folks. I am trying to figure out what gears to go with in my Jeep. I have a daily driven 84 CJ-7 with the 258, Weber38/HEI/Borla with 75k. The tranny is a BW/WC T-5.
Currently, I run 33x9.5x15 BFG All-Terrains on the street, and 31x10.5x15 Swampers(soon to be replaced with 33x12.5x15's) off-road. My axles are currently 3.31. I 'wheel on a combo of mud and rock usually, with infrequent excusions on the highway.
I want to go somewhere between 4.10 and 4.56. I measured my BFG's and they actually are 15.5 inches from the ground to the center of the hub, so actually are 31" tires. I am pretty sure my T-5 has an overdrive of .86..could be wrong, i see conflicting info on the Web...
According to my calculations, 4.10's would give me 2484 rpms @65 mph and 4.56=2762 rpms @65(using gear ratio X mph X 336 X 5th gear ratio/tire size)
Sooooo..anyone who has experience with any of these combo's let me know what your opinions are of these choices. Right now I am more inclined to go with the 4.10's but want to make sure I make the best possible guess!
TIA
Bob




 

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I run 4.56, t-176, and 33in Swampers. With the 33's and a four speed fwy travel sucks; I only use the CJ for wheelin so this isnt a problem. If I were going to drive it daily I would go 4.10.

Rob

83 CJ5 4.2 t176 300 4.56 33s
 

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/wwwthreads_images/icons/crazy.gif Er....ah, Bob.....my moonguys/wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/smile.gif/wwwthreads_images/icons/laugh.gif just told me that they calculated this at 2667/2293 Direct/Over with 4.10's.....and 2966/2551 Direct/Over with 4.56's....figured at 60 MPH. Are you sure about those numbers? Your RPM seemed low to me, so I had the moonguys run the calcs./wwwthreads_images/icons/crazy.gif I came up with 650.5 turns per mile, which when multiplied by the rear end ratio give the RPM @ 60 MPH

CJDave
I never believe any statistics unless my moonguys /wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/wink.gif made 'em up themselves.
 
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I also own an 84' CJ-7 that is my daily driver. It is a five-speed and I recently put 4:10' s in it. I have 33x12.50 BFG MT's on it and think I made the right choice for gears. It accelerates better, does great off-road, and still ok on the road. Hope this helps.

 
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Bob,
You do want to run 4.10s, this is the best all around gear for you, if you were running 4.56s or 4.88s, then you should run,35" tires, that would be the combo for all around, but if you were not going to drive it fast on the fWY, or on long trips, the lower ratios work better for four wheeling. Hope this helps.
The Doc

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Mike Duncan
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Discussion Starter · #6 ·
How about a 4.27 ratio gear set? I am pretty sure it's available, and the ratio would be 4.27x.83x65x336/31=2496 RPM at 65...
I am hoping someone will tell me if I'm right about the OD in my WC T-5 According to www.advanceadapters.com/BUYERSGUIDE/bgjeep.html#13 my tranny has a 17% OD ratio. That IS .83, right??? anyone?
I think I need to buy a tach and SEE exactly what RPM I am currently turning as opposed to what it feels like...I just dont wanna make a wrong choice in gears.
 
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Bob,
4.10s to 4.27s in RPMs would be about 112 RPM more, that would be ok, but dont run 4.56s. I dont think you will like them, dont forget that when your on the highway, and if your pulling a grade, you'll be in 4th gear, unless you have a really good running jeep, 4th is going to be about 3,017 RPMs, most cjs with carbs dont like to run much over 3 thousand RPM, If you had a fuel inj motor, thats a differant story.
The Doc.

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Mike Duncan
[email protected]
 
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