YAY! Another regear question, but this one is different!

Okay, so I have a 1995 XJ with the RC-D30 and 8.25" axles:

1. I don't want 4.10s or anything that high(numerically)
2. I don't plan to run anything but 30s(*MIGHT* got to 31s eventually, but not for a *LONG* time).
3. I do some light/moderate towing.

So here are the questions:

Where do I find 3.91s for my RC-D30(obligatory "where do I..." question)?
Has anyone regeared to 3.91s(obligatory "has anyone..." question)?
Are 3.91s THAT much better than 3.73s?(3.73s are much easier to find)
Will 3.91s work with a factory TracLoc, or a TrueTrac(<--I think that is the gear driven LSD)?

I'll edit this if I have more questions, but I would really appreciate some input on these questions. Thanks for helping.

Fergie

Sorry but I dont know of anyone w/ the 3.9 series gears for the D30.Go with the 3.73's.

And if you could find 3.90, then you might as well go 4.10.

One big question:
is your XJ stick or auto?

If stick.. then definately think about 4.11's. I have my stick with 4.11's and for about 8 months I drove with 235's on... and except it ran high rpms' at 80mpg (about 3K or so, but it's well within tolerable range) I loved it!!!

Kejtar

It is an auto. I REALLY dont want to go into the 4.XX range because I dont need to. I am going to run 30s for a very long time.

I have been looking though, and it looks as though 3.73s are the only way to go(unless someone knows something I dont)

Fergie

If you want to look at the numbers, I set up a spreadsheet that lets you put up to three setups side by side and graph them speed over RPM. If you want to send me your Email on a PM I’ll send it to you.

I was also going to go to the 3.93's but the shop then discovered I had a 8.25 in the rear(no tag and I bought it used). I am planning on going to 31's this year but I also tow a 3500lb camper often. I have an auto and was thinking of going up to the 4.11's but the shop said I should be running at least 33's before doing that. Yet I have seen charts which list the 4.11's as being in an acceptable range. I tow pretty long distances but it's also my daily driver and I don't want to run high rpm's every day. I have a 94 sport and am currently running 235/75R 15's. On mild hills while towing the stock gearing is adequate at best. But on steep hills I can't even hold my speed. Anybody out there have a similar situation? Any input or advice would be greatly appreciated.

if yours is auto, then you have 3.55's....

going to 3.73 or 3.9 IMHO is not worth it.

You will probably NOT feel the difference on such a small jump.

At 65MPH in overdrive(.71), and 30" tires (30.0 used in equation) your rpms will be:

3.55-1835
3.73-1928
3.92-2026

I'd save your money. I think it would be more important to dial in your gearing on a stick, since you have a "direct hook up", but you are lucky to have a torque convertor working for you....

Beez hit the nail on the head - don't bother jumping up a single increment - you will not notice much difference and your auto will be very forgiving...

I held out and ran 33" boggers with 3.55 gears and an auto - it still cruised down the freeway fine (was a little lacking on the hills) but my next jump was up to 4.88's - which I loved with the 33's but are just ok with 38's

6.5:1 would be what I would run now if the RC could accept it but unfortunately 4.88 is as deep as the RC30 can go - perhaps when I get bored down the line I will add a 9" center section to the tubes and outers I have now... probably not; but who knows

Plus with the D30, a different carrier is required beyond the 3.55 you likely have with your auto. The 8.25 carrier is good for all available ratios (3.92 may be avail in Dodge p/u?)

So...since gearing up to 4.xx isn't in the cards...maximize what you have 'around' those factory gears. Having a shop regear both ends is a fairly expensive upgrade, but if you could get ahold of used 3.73 gears & a front carrier at low cost, did the swap yourself etc...it wouldn't be a 'stupid' upgrade...just not a lot of 'bang.' With that in mind:

In 12-2000 Petersens 4W&OR mag did a bolt on upgrade for a (stock 96, AW4 3.55:1) HO 4.0 Using Turbo City parts. They did a cat-back, airtube/K&N, bored TB, MAP adjustor (A $635 kit, but the MAP cost 8 HP so it was deleted for the final test...without it it would be a $550 kit)

Rear wheel HP/Torque peak #s:
Stock HP: 135 @ 4200-4400; Torque: 193 @ 3000
Modded HP: 158 @ 4400; Torque: 216 @ 3000
Stock HP at the torque peak rpm: 110 @ 3000
Modded HP " " : 127 @ 3000
Using $544, thats $24 per extra peak HP and LB/FT (pretty cheap really)

I'd suspect that adding a 'good' header like a Borla, a free flowing head pipe, hi-flow cat would add a bit more oomph, though maybe not where you need it in the RPM band. A higher performance cam ICW those other goodies should help too, but remember that you aren't really after top-end HP. It seems that the torque #s down low increase along with the peak HP, which is good

A 'nut' could take all of the above, then clean up the head/manifolds (gasket match) for more flow, and have a pretty healthy 4.0l but at what point ya want to quit $pending and/or sinking hours of labor/downtime into your Jeep is a question.

DAMN!!! I hate it when resonable people speak up. J\K though, thanks for all the input, as you will prolly end up saving me some money.

I already have a custom cat-back form the local muffler shop, and willl have an ARB snorkel soon...($150 brand new...hahahaha). I want to keep the engine as basic as possible, not doing anything that will decrease its longevity, but adding a little power.

The reason I ask about the *small* regear, is that I noticed a difference going from the 225s I had, to the 30s on there now. I am semi-concerned about gas-mileage, but buying gas is necessary, and I am no leadfoot. Hell, I drive at 68mph on the interstates(drives my gf crazy, shes from MD).

My concern is lugging the engine, or putting too much stress/strain on drivetrain and parts. I want my XJ to last a VERY long time. And I figure a regear will solve this dilemma.

Thanks for reading so much, and keep the comments coming.

Fergie

I have a 2000 with 31's running 3.55's....I added some of the above mentioned power adds and noticed a BIG differance......on hills that made my jeep down shift before were no problem.......I wouldn't waste the time to re-gear in your situation....just my 2 cents

Dodge Dakotas and Durangos came with a 3.91 or maybe it was 3.92 gear ratio. Some of them I know have a six lug 8.25 rear axle, that would get the rear gear ratio. The front is IFS, I can't confirm it but it sure looks like a D30 center section, it wouldn't be reverse cut, but it might be something to check out.

mac '4.10s are the answer to everything' gyvr

Well, I recently added a high flow intake and a Gibson stainless header. I will hopefully get a bored out throttle body here in a month or 2. I put a custom 2 3/4 in cat-back on about a year ago but I still have the stock cat. I haven't towed the trailer yet since adding those mods so I will evaluate the situation then. The cat might be going soon anyway, there's somethin rattlin under there somewhere. Gonna hit the exhaust shop tuesday to have them give it a look. Thanks for the info and opinions. Further ideas or views are welcome as well. I love these new forums.

Find a d30/d44 out of a 80s xj with towing package (3.73s I beleive) would be the only way I would.
I'm on 31s and actually regearing soon cause I have a very cheap oppurtunity to do it. I was planning to stay on 3.55s cause it runs awesome with them (87 renix + motor mods) has no problem keeping up with traffic on the hills and can hit most of them in OD. Even though it does run awesome I suppose theres room for improvement so I'll give it a try
I'm putting a built lsd in my 8.8 and better springs so while I'm at it found brand new mustang 4.10s for 100$. Then found a non CAD D30 out of a 86 2.8l xj with factory 4.10s which I will build to my liking maybe even finding a used ARB locker for it in time. So like 200$ to regear in my case plus a better front axle and maybe some extra goodies which won't take much extra effort to do while I'm at it.

8 year old thread back at the top.. right on..