Gear ratios and bad advice

billiebob

TJ Addict
Supporting Member
Oct 31, 2015
3,564
Kootenays, BC, Canada
6-speed manual NSG370
33's - 4.10 more street, 4.56 more trail or mountainous/hilly highway
I drive 24K miles every year, mostly pulling a trailer in the mountains. With 33s and 4.10s. I wish I had 3.73. All too often I will be on a long steady downhill wishing I had one more gear.... or 3.73s That is real world experience, anyone else here put 24K miles on every year, towing a 2000 pound trailer for most of those miles? ... in the mountains?

75251
 
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AndyG

TJ Addict
Supporting Member
Jul 30, 2018
2,098
Alabama
All the math people use kills me ...and I have seen some real keyboard battles over gearing and octane ......I know it satisfies the mind ...but you can pretty much ask experienced owners like Jerry Bransford , Rob or Chris and end up fine .

Tire sizes vary, they actually become smaller every time you drive the Jeep , and if you get in the ball park you will be fine .

Most folks want to figure it all out ...it's when you first drive the regeared Jeep that you really smile .
 
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Steven

New Member
Jun 19, 2018
24
Ontario
Sorry, a little bit off topic here, but recently found a good deal on a D30/D35 with 4.88 gears. However the rear is disassembled and has a welded diff. If I were to make the buy, and take the ring and pinion off and just use the carrier that is currently on my jeep (also a D35) would that hypothetically work? I checked the teeth on the gear and pinion and everything looks great, and the asking price was below the cost of the gear sets themselves.

To put into perspective, I'm currently running 33's on the stock 2.5L with 4.10 gearing and having to sit in 4th around 3050 rpm at roughly 110km/h (roughly 70mph). I would like to upgrade the rear axle in the future, but for the time being I'm just doing light Overlanding so I have no desire to run anything over 33's, or get lockers for now as it is the D35.

Question being - would it be worth grabbing the axles and putting the two rears together?

Again, sorry for being a little off topic. Just looking for some advice before doing anything I regret.
 
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JMT

The Jeep Guy
Supporting Member
Ride of the Month Winner
Feb 27, 2017
7,605
Texas Hill Country
All the math people use kills me ...and I have seen some real keyboard battles over gearing and octane ......I know it satisfies the mind ...but you can pretty much ask experienced owners like Jerry Bransford , Rob or Chris and end up fine .

Tire sizes vary, they actually become smaller every time you drive the Jeep , and if you get in the ball park you will be fine .

Most folks want to figure it all out ...it's when you first drive the regeared Jeep that you really smile .
I should get to drive mine for the first time today. :)
 
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chuck72

New Member
Mar 26, 2018
4
Cleveland, TN, USA
i think I've finally found the answer to a question I have been struggling with. I have an 04 tj 5spd. just regeared to 4.56 in preparation to lift and bigger tires. If I am reading and understanding right. 33' tires would be perfect for daily driving and weekend trail riding.
 

AndyG

TJ Addict
Supporting Member
Jul 30, 2018
2,098
Alabama
i think I've finally found the answer to a question I have been struggling with. I have an 04 tj 5spd. just regeared to 4.56 in preparation to lift and bigger tires. If I am reading and understanding right. 33' tires would be perfect for daily driving and weekend trail riding.
That's my set up..it's great .
 

Yendra Built

New Member
Mar 13, 2019
5
Laporte, CO
Soooooo.... I have a 2004 TJ with the 2.4 with 4.56 gears and an automatic and that thing constantly was dumping overdrive. I couldn't drive 75 on the highway without it jumping in and out of OD constantly with the stock little tires.
So one day driving home from the shop the 2.4 dumped its water and seized up.

Now the good news, after researching and looking for something better to replace it with and coming to the conclusion that an LS swap may be the way to go I find on craigslist a 2005 TJ chassis with no body and all the running gear. This thing came with the pedals, the steering column, 4.0 engine, axles (3.07 ratio) and best of all the Mercedes 6 Speed. Now a lot of people may think that 3.07 axles are the way to EPA enlightenment but I'm not buying that, the 4.56 axles are staying. I live at 6200 feet and at that altitude those gears are going to be perfect. This also gives me options for bigger tire sizes later.

My heavy 2000 F250 has a V10, a ZF 5 speed and 4.30 gears and it gets up to 13 MPG because of running a higher manifold vacuum at cruising speed and the fuel rail pressure regulator and ECM, make use of this and therefore it cruises very easily at any speed. And not only that I can pull the 7000 LB boat with ease.
EPA is ideal and probably sea level conditions. In the real world bigger ratios are usually a better way to go and with better drivability.