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Discussion Starter · #1 ·
I am presently running 33x12.5x15 tires on a 2000 Jeep TJ Wrangler Sport with 3.07 gears (only option from factory in Oz).

Anybody aware of any difficulties with the 5th gear in the TJ's for cruising and is the 3.07 axle up to taking a 4.1 comfortably or should a 3.73 be preferred?

No real bouldering in Oz but definitely need to be able to cruise long distances so I don't want the engine screaming.

On paper 5th seems to put me at 2,040 revs in 5th with the 4.1s, which sounds perfect. But I am told it may be closer to 2,400 given the actual rolling resistance diameter of 33 inch BFG muddies.

I want to be reassured as to the 4.1 plan!


clay
 

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I believe you have a Dana 35c in your TJ, same as my 88YJ. I am running the stock 4.11's (came with the 4cyl back then) and
have decent cruising rpm's with my 33's. I wouldn't mind going down to 3.73 since my V8 can still turn them. Depends on how
much you want to spend on gas, I get 10mpg, but will have 35's on in a month or so, Which will lower my rpm's slightly.
4.11's should fit in your carrier though, but I have never hear of a 3.07 so it may be a unique carrier? What kind of 5th gear OD
do those 2000's come with? <.80 go with a 4.11, over .80 go with 3.73 (you'll still feel a MAJOR difference from your 3.07).

/wwwthreads_images/icons/cool.gif Big Ed
'88 YJ, 4" susp,3" body,33's,283 Chevy V8,TH350,4.11's,D30,D35c
 
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Discussion Starter · #3 ·
Clay,

I have a '97 Jeep Wrangler. I picked mine up from the dealer with 33-12.50 BFG's on 15-10 inch rims. It also has the 3.07 axle ratio. I don't know why Jeep even offers this ratio or the 3.73 (in 1997 the optional axle was a 3.55) for the I-6 engine and not the 4.10 ratio included on 4 cylinder Jeeps. I got the 3.07 because I didn't want to wait for another Jeep to arrive at the lot, and it was late in May when production was starting to get changed over. Jeep also had a strike at the factory that made the I-6 engines adding to delay times. I just figured that I would change it eventually, so why pay for an upgrade from the factory that was going to get changed. My Jeep runs fine on the highway under 60 in 5th gear, but it needs to be regeared. I am going with the 4.10 ratio when my cash flow permits it. As for your question on which axle ratio is preferred, these links have usefull information that will help you decide.
http://www.off-road.com/jeep/projects/tj/tjintro.htm
http://www.off-road.com/jeep/tech/tjgears/index.htm
From the information I have encountered, most people think that the 4.10 is the way to go with 33 inch tires. The link has a formula that will give you engine speed with different tire sizes and gear ratios. I hope this info help you.Sorry for the long post.

Dan

99Tahoe_Dan
 
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Discussion Starter · #4 ·
I don't know what kind of transmission you've got but I can speak for my 5-speed 99 tj with the i-6, and say that if my gearing put me at 2,000 rpms at a reasonable highway speed of 70mph, I highly doubt that I could maintain that speed unless the road was perfectly flat and I had a nice tail wind. I have the 3.07 gears and 31" BFGs and in 5th there is not enough power to maintain 70 mph if I'm facing any type of hill or head wind, or have the top off. With 3.07s and 33s, I would have to guess that pulling out in first gear would be a real bitch. If I was you I'd drop that 3.07 like a bad habit and get 4.1s. I'm not looking at the owners manual, but I would have to say I think the reccomended rpm at highway speed was at the least 2500.

Mike

 
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Discussion Starter · #5 ·
Mike,

I am going to drop the 3.07 as soon as I have the cash. On the highway, up to 60 MPH my Jeep does fine unless a somewhat steep hill is encountered. I am not sure how fast I am actually going, because I have had my spedometer fixed by the dealer 4 times. I have used another vehicle to guage my speed based on their speedometer readings. When I got my Jeep, I it wouldn't run 70 unless the pedal was on the floor after power shifting out of 4th gear. Because of the spedometer error, I was actually driving at almost 90 miles an hour. I was also stopped by a police car when the car was a month old. He didn't have time to get me on radar, but he said I looked like I was speeding. Most of my highway driving is in Atlanta, Ga and the surrounding area where hills aren't too bad. At 70, My Jeep turns just under 2000 RPM's. At 70, any hill requires a shift to 4th, unless I am behind another truck, or the hill isn't very steep. That's just one of the things we have to deal with until we can upgrade.

Dan

99Tahoe_Dan
 
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