I have a 67 cj5 with 33" mud terrains. Im in the procces of a different rearend due to transmission swap. It will be used offroad but also on the hiway.The front wich is the only one i have and installed is 4.88 and i the rear that needs to be installed has 3.73 so i have to pick a ratio and do some switching.wich one would be best?
3.73 OR 4.89 gear ratio?
- Thread starter Tyler 67
- Start date
Bounty__Hunter
Super Moderator
Which engine and transmission?
Different gear ratios are more suited to certain engine and transmission combos.
Different gear ratios are more suited to certain engine and transmission combos.
William1982CJ7
New member
I'm far from being an expert but some thoughts....Definitely recommend a overdrive with 4.89 and 33"s . Would be great off road but on the highway your rpms will be pegged. Had 4.56 with 35's with a 3 speed and I was screaming on the highway.
I agree with bounty hunter as well.
I agree with bounty hunter as well.
Bounty__Hunter
Super Moderator
Not real familiar with the RPM's that engine works well with, but with the 3spd and no overdrive you may want to stock with the 3.73 gears. If the engine doesn't mind high RPM's, or if you limit your highway driving and want better offroad performance, go with the 4.88 gears.
Rubiconrich
New member
3:73's are not bad just don't put a tire bigger then 33"s.
4:88's are for back roads and Big tires 35"s
4:88's are for back roads and Big tires 35"s
The Buick 225 is not a high rev engine, it is well known for almost diesel like low end torque due to the very heavy flywheel. Since you are swapping axles I would swap in a Narrow track D30 up front as well, or a wide track if you want a little more stability. Nobody wants them so they are cheap. Either axle is a bolt in swap for your D27, you just need to adjust the tie rods. Speaking of tie rods, I would also seriously consider changing over to a Saginaw steering from your Ross style, much easier to keep aligned and less play makes for more enjoyable driving. The D27 has a lot of weak points, design flaws, and obsolete ($$$) parts in it. It is the weakest front diff Dana/Spicer ever made. The 33" tires are going to prove to be a little too much for that axle in the long run. I have only seen 5.38, 4.88, 4.27 gears in stock for the D27,25 axles. I have seen 3.73 but they have been discontinued. There are many more gear selections for the D30, not to forget the D30 has much improved brakes, some even with disc brakes.
I did the NT D30w/disc brakes swap on my CJ2a and am very happy I did. Unfortunately it wasn't until I had dumped a ton of money into rebuilding the D25.
I did the NT D30w/disc brakes swap on my CJ2a and am very happy I did. Unfortunately it wasn't until I had dumped a ton of money into rebuilding the D25.
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Rubiconrich
New member
The last guy beat me to it. Yes look for a Dana 30 with 3:73's and disc brakes.
RangerRick
New member
Yes, Wide track came in mid 82 & UP CJ7 & CJ8 Scramblers. All have disc brakes and you may get lucky to find one with 3.73's or 4.10 gears which would at least let you drive on the highway. 4 cylinder CJ7's & CJ8's were more common to have 4.10's in the last couple years of production when coupled with a manual transmission.
Rick
Rick
Bounty__Hunter
Super Moderator
I didn't think you could swap in a WT front axle without outboarding the spring hangers.
