Please convince me not to go to 4.88s

[RoadRanger]

My new-to-me '98 has 4.10's with the 2.5L . The present tires are 32's which I plan on staying with (or maybe 33's?). 1st is too high IMO as is 5th. I see 4.54's recommended for this setup but I never drive over 65 and would like as low a low as possible even though I don't want to do black trails - which would be a bit stoopid with Dana 30/M35 anyways. I calculate just a bit over 2800 RPMs at 65 - am I going to hate that?

 

[L J]

I calculate just a bit over 2800 RPMs at 65 - am I going to hate that?

You shouldn't as that is right in the sweet spot. With 32" tires there is only ~200 rpm difference between 4.56 and 4.88 gears at 65 mph (~2700 with 4.56 / ~2900 with 4.88). Based on your information, 4.88s would be the choice.

 

[TheBoogieman]

4.88s with a S35 and never look back. Those 4 squirrels love higher rpms.

 

[RoadRanger]

Thanks!

 

[jjvw]

...

 

[rasband]

42rle/30”/5.13=2973rpm@75mph

Their profile states an AX-15 transmission, in case that changes things.

 

[jjvw]

Their profile states an AX-15 transmission, in case that changes things.

AX15/31"/4.56=2928rpm @ 75mph
AX15/31"/4.88=3134rpm @ 75mph

 

[L J]

Their profile states an AX-15 transmission, in case that changes things.

AX-5

 

[jjvw]

AX-5

AX5/31"/4.56=3151rpm @ 75mph
AX5/31"/4.88=3372rpm @ 75mph

 

[L J]

AX5/31"/4.56=3151rpm @ 75mph
AX5/31"/4.88=3372rpm @ 75mph

... I never drive over 65 ...

 

[machoheadgames]

AX5/205/4.11=3344rpm @ 75mph
AX5/32/4.88=3400rpm @ 75mph
AX5/32/5.13=3575rpm @ 75mph
AX5/33/4.88=3291rpm @ 75 mph
AX5/33/5.13=3460rpm @ 75mph

Go with 4.88’s if you’re doing 32’s, or 5.13 if you’re doing 33’s. 33’s are a lot heavier power-sucking than stock 205’s, so you want more gearing to make up for that. Decide on what tire you want first, don’t think you may stick to 32’s, go with 4.88’s, then switch to 33’s because that ends up being a half measure. If there’s any chance of 33’s, just do the 5.13’s.

 

[Apparition]

 

[MBDIAGMAN]

To the OP:

I’m surprised the 4.10’s don’t seem to work, but maybe the four banger(I’ve never driven one) needs a little more gear. Modern engines of all brands and sizes don’t mind being revved up like they used to be. Also, remember that your four cylinder fires twice every revolution vs three times for a 4.0. That makes it sound differently, so go by feel, which I think you are. If the engine is in good shape, holding good oil pressure and being properly cared for, don’t be afraid to spin it up a little. I run 4.88’s with a 4.0, 35’s and 6 speed and they’re perfect. I would think that to let that engine rev a little, 4.56’s and maybe even 4.88’s would be fine.

Since it’s not an easily or inexpensively reversed change, it would be nice if you could find someone with one of these gear sets and drive it, but that would probably be hard to find.

We are all different about such things, but if it were me, I wouldn’t fear the gear.

Hope this helps.

 

[RoadRanger]

An alternative would be to swap in a 6-speed with its lower first gear - has anyone done that? 6th (AKA overdrive) would still be mostly useless (below 70?).

 

[machoheadgames]

An alternative would be to swap in a 6-speed with its lower first gear - has anyone done that? 6th (AKA overdrive) would still be mostly useless (below 70?).

While it’s ratios are ideal, it’s such a poor shifting transmission that most have better luck with the 5 speeds.

I’ve been in several gear threads lately and am getting mixed up. Since this one is a 2.5L, no, you cannot install the 6 speed unless maybe a bell housing adapter exists. Otherwise it’s 4.0 only.

 

[Wildman]

People can offer gear input all day long but until you've driven a 4 popper it doesn't matter.

As a former 4 cylinder owner I'll tell you right now if you have any thoughts about going to 33" tires then you'll want 4.88 or 5.13 gears. I live in central WA so I used to drive over Snoqualmie pass on a regular basis. My TJ had 33" tires when I bought it and at the time 4.88 gears were the deepest gears you could buy. Installing 4.88's gave me the use of 5th gear back on the flats & slight uphills. Still had to drop to 4th or 3rd on steep climbs which is why I'd suggest 5.13 gears.

I swapped out my 4 cyl for a V-8 almost 20 years ago now but I'll admit there are loads of times I miss the 4 angry squirrels. One other thing to note is if you plan on keeping the Jeep & run larger tires at some point your AX-5 most likely will give up the ghost. When & if it does swap to a AX-15 transmission.

 

[Rickyd]

One other thing to note is if you plan on keeping the Jeep & run larger tires at some point your AX-5 most likely will give up the ghost. When & if it does swap to a LS engine.

Amen brother.

 

[Wildman]

Amen brother. Only a FOOL would ever suggest a Lame Shit engine swap

FIFY....

 

[MBDIAGMAN]

An alternative would be to swap in a 6-speed with its lower first gear - has anyone done that? 6th (AKA overdrive) would still be mostly useless (below 70?).

I would not do that. The six speed doesn’t have the durability reputation of the five speed. The gear ratios are probably more desirable, but I would not recommend it unless you have considerable experience with an old world, sliding gear, unsynchronized gear box.

If you insist though, I would consider the trade.

 

[Wildman]

Amen brother.

Sorry I clicked the wrong button and changed your post... Tried to restore it to what you'd wrote...

I would not do that. The six speed doesn’t have the durability reputation of the five speed. The gear ratios are probably more desirable, but I would not recommend it unless you have considerable experience with an old world, sliding gear, unsynchronized gear box.

If you insist though, I would consider the trade.

As others have said the 6 speed isn't a viable option. Regear it for the size tires you want to run and be done with it...