Josephangelo Posted June 19, 2020 Share Posted June 19, 2020 I'm looking for suggestions about gear ratio. I just bought a 1988 Comanche. 4cy, 2wd, manual 5speed. I got 31 inch tires for it. I will be using it as my daily driver on highways and city streets. I will NOT be using it off road. I think the stock gear ratio will not need to be upgraded. I was wondering if anyone had an informed opinion on this. Thanks Link to comment Share on other sites More sharing options...
89 MJ Posted June 19, 2020 Share Posted June 19, 2020 You most likely have 4.10 gears. Those will be fine. Link to comment Share on other sites More sharing options...
DesertRat1991 Posted June 19, 2020 Share Posted June 19, 2020 Need is subjective. You are definitely gonna feel the difference. Especially, if you are stepping up from stock 26.5" tires. 4.88's will return you to near stock performance. Link to comment Share on other sites More sharing options...
Eagle Posted June 19, 2020 Share Posted June 19, 2020 With a 5-speed, you should have 4.10 gears. Asking for advice after you bought the tires is unfortunate, because my advice would have been to NOT buy tires that big. The 4-cylinder isn't going to be happy trying to roll those big tires. Unfortunately, DesertRat is incorrect. Even 4.88 gears won't get you back anywhere near stock. Your factory tire size was probably 195/75-15, and the RPM in fifth gear at 60 MPH would have been 2411. With 31" tires, 4.10s at 60 MPH will only have the engine turning 1842 RPM at 60 MPH, and 4.88s will only bump that to 2192 RPM. That's way below where the 2.5L likes to run. Link to comment Share on other sites More sharing options...
MiNi Beast Posted June 19, 2020 Share Posted June 19, 2020 Link to comment Share on other sites More sharing options...
derf Posted June 19, 2020 Share Posted June 19, 2020 I'll echo what Eagle says. I'll also add in that where you live will make a huge difference. If you're in the flat lands of the midwest prairie, you don't need as much gear as you do if you're in the mountains, especially as elevation goes up. Depending on your original tire size, stepping up to 31's needs at least 4.56 gears minimum to return to "factory" performance. Even then, you will want better than factory so 4.88's would be a good choice. If you're at high altitude with lots of hills, 5.13s would be better. Link to comment Share on other sites More sharing options...
Pete M Posted June 19, 2020 Share Posted June 19, 2020 offroad is actually easier to run big tires on stock gears because the transfercase helps when in low range. you're not the first to do it, and won't be the last. the only one that can say for sure if it's acceptable is you after putting some miles on her. Link to comment Share on other sites More sharing options...
mnkyboy Posted June 21, 2020 Share Posted June 21, 2020 5th gear might not be very useful but otherwise it will drive ok, your effective ratio will be similar to a stock 4spd truck. Link to comment Share on other sites More sharing options...
Josephangelo Posted June 21, 2020 Author Share Posted June 21, 2020 Thanks for the help everyone Link to comment Share on other sites More sharing options...
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