Talk me into (out of?) 4.88's

Kejtar · Apr 20, 2004

OK, so I'm still at the research point. I already reached the conclusion that I will be getting a detroit for the rear, but the next question is gears: 4.56 or 4.88? After installing the gears I will probably be running my 31's for a short while (2 months? 3 months?) for abotu 120 miles a day and then I will be going to 33's (or maybe 32's? but most likely 33's) and still drive about 120 miles a day (I am looking for a DD rig but nothing interesting came up yet). Anyways, I talked to some people and few regretted not going with 4.88's with 32's and few said that 4.56's are more then enough. Anyways, the XJ is a stick so take that into account, as well as the fact that I do like to get it up to 80 when the freeways is truly a free way (rare, but yes, it does happen in the LA area

).

Also if you do happen to drive a stick shift with 31's or 33's and 4.56's or 4.88's please post your rpm's @ 65, 75 and 80 mph.

Kejtar

BrettM · Apr 20, 2004

i'm currently on 33s with 4.88s and auto with .75 od, the RPMs are perfect or a tad high (70-75mph). I have 35s that will go on next month. an AX15 has an od of .79, so your RPMs would be even higher. if you really are going to stay 33s or smaller, I say get 4.56. then you also keep one more pinion tooth on the D30.

Weasel · Apr 20, 2004

Mad,
Wha kind of RPM's are you running at 75-80? And your MPG? I was thinking 4.56 for 33's and auto would be fine.

Beezil · Apr 20, 2004

dude, get your ducks in a row.....

wtf is up with people not being able to control themselves?

do tires and gears TOGETHER.....

if you think you have some good reason why this can't happen, wait until your ass squeezes your head out of it to realize how badly you lack patience.....

my feeling is that your temporary tire size to new gear ratio is entering in as a determining factor....

if it isn't, it wasn't worth mentioning.

Kejtar · Apr 20, 2004

Beezil said:
dude, get your ducks in a row.....

wtf is up with people not being able to control themselves?

do tires and gears TOGETHER.....

if you think you have some good reason why this can't happen, wait until your ass squeezes your head out of it to realize how badly you lack patience.....

my feeling is that your temporary tire size to new gear ratio is entering in as a determining factor....

if it isn't, it wasn't worth mentioning.

Actually the tire to gear ratio ratio is not going to be much of a factor: I drove around on 235's and 4.11's for over a year

In any case if I spread them over two or three months I can do it. Otherwise I'd probably spend the money on something else while waiting (I'm not that patient LOL)

red87cherokee · Apr 20, 2004

Kejtar said:
Also if you do happen to drive a stick shift with 31's or 33's and 4.56's or 4.88's please post your rpm's @ 65, 75 and 80 mph.

Stick shift, 31's, and 4.88's.

55 = 2350 RPM's
60 = 2550
65 = 2750
70 = 3000
75 = 3200
80 = 3400
85 = 3600

Note, in Oregon the max speed limit is 65 and the nearest freeway with a 65 speedlimit is over 100 miles from where I live . . . so, all speeds over 75 are calculated, rather than observed.

BrettM · Apr 20, 2004

Weasel said:
Mad,
Wha kind of RPM's are you running at 75-80? And your MPG? I was thinking 4.56 for 33's and auto would be fine.

i don't know for sure what RPMs for what speed because i haven't corrected the speedo gear yet, i'm guestimating 3100 at 75 though.

my MPG was 17 with 33s and 4.10s, and i'm using much less throttle when cruising at 70 now, so I'm gonna guess right about 20 mpg.

this is all on an '88 Renix 4.0 with 200k miles, '94 AW4 tranny, shortbed MJ, probably an extra 150 pounds of tools and junk, 7" of lift, K&N mounted on top of throttle body, no muffler (not that loud actually)

Buck Jackson · Apr 20, 2004

I don't know how you guys can run such low gears on the highway. In my DD I have 4.10's and 33's. This gives me relatively stock feel on the highway, but is not quite low enough offroad to crawl around. Fortunately mine is a family/camping rig. When i next feel the need to do something to the drivetrain it will be to add a Klune-V or maybe a Teralow.

BrettM · Apr 20, 2004

i have now driven:

3.07/stick/28s
3.07/stick/31s
3.55/stick/33s
4.10/stick/33s
4.10/auto/33s
4.88/auto/33s

the last combination is definitely my favorite, even on the highway, though I do look forward to the 35s to bring down the RPMs just a bit

basalt51 · Apr 20, 2004

33 go 4.56
35 go 4.88

33s, 4.88, auto, ~80 = 3000 rpm to high for my 120 mile daily commute.

ChuckD · Apr 20, 2004

If you go 4.88's definitely go 33's. I think you'll like it, 2500 rpm's @ 65 in fifth. 85 is around 3k. It is very tolerable and I like it. It's the way I had it when I had 4.10 and 31" tires.

How big of a difference is there between the 4.56 pinion and the 4.88 pinion really. I wanted better crawl ratio on the trail with out going to a new tcase.

When and if I ever go with bigger tires I'll probably stay at 4.88, and add a 5 to 1 Atlas or 4 to1 Rocktrac. Also I'll have a D44 in the front. My MTR's are doing me well right now, next tires may be traxus MT's for the price, but I do have that tire warrenty.

If I break the 4.88's, I'll be the first to admit that the pinion is too small. I know for a fact that the joints and shafts will still be the weakest link.

ChuckD · Apr 20, 2004

basalt51 said:
33 go 4.56
35 go 4.88

33s, 4.88, auto, ~80 = 3000 rpm to high for my 120 mile daily commute.

He has a stick!

BrettM · Apr 20, 2004

ChuckD said:
If I break the 4.88's, I'll be the first to admit that the pinion is too small. I know for a fact that the joints and shafts will still be the weakest link.

my friend blew both 297s, yokes, ring and pinion on his HP D30 with 4.56s all at the same time. also blew the rear D44 yoke. he was trying to tractor pull with a stock Exploder.

also, Keijtar has a 98, which is a low pinion diff (right?) making the D30 gears even weaker. but it's probably not a concern either way on 33s

Kejtar · Apr 20, 2004

ChuckD said:
How big of a difference is there between the 4.56 pinion and the 4.88 pinion really. I wanted better crawl ratio on the trail with out going to a new tcase.

That's what I'm thinking actually. Or rather I'm thinking what's the big difference from 4.11 to 4.56? When I went from 3.07 to 4.11 I saw the difference.

If I break the 4.88's, I'll be the first to admit that the pinion is too small. I know for a fact that the joints and shafts will still be the weakest link.

Yeah..... I have a feeling that I will be spending some $$ not too long after putting the gears on some shafts and so on... but that will have to wait till after the tires

Kejtar · Apr 20, 2004

mad maXJ said:
also, Kejtar has a 98, which is a low pinion diff (right?) making the D30 gears even weaker. but it's probably not a concern either way on 33s

98 is an HP

MaXJohnson · Apr 20, 2004

When making these comparisons, keep in mind that most tires don't run true to size. The 31's I just got rid of measured 29 1/2" with half the 19/32" of tread gone. The 33's that replaced them measure an 1/8" under 33" which is within my tolerance of error (+/- 1 sixpack). I've read previous reports that the 35" MTR's are not much taller that 33".

My so called 31's tached 3000 RPM at 70MPH with 4.10 gears and a stick. With the 33's, at 3000 RPM I'm doing just under 80 MPH.

Your mileage may vary. Then again, it may not.

BrettM · Apr 20, 2004

my 35" MTRs at about 75% tread mounted on 10 inch wheels measure a solid 34.5"

Kejtar · Apr 20, 2004

mad maXJ said:
my 35" MTRs at about 75% tread mounted on 10 inch wheels measure a solid 34.5"

hmmm 35's???

ok... maybe not yet

lol Anyways, looks like I reached a decision: I will be going 4.88's and Detroit and 33's

now l just gotta find me a bank and a driver

LOL

BrettM · Apr 20, 2004

i was just looking at your sig, are you keeping the 8.25? can you get 4.88s for it? i thought i remember hearing of frequent problems with putting low gears in those...

MaXJohnson · Apr 20, 2004

mad maXJ said:
my 35" MTRs at about 75% tread mounted on 10 inch wheels measure a solid 34.5"

MaXJohnson said:
Your mileage may vary. Then again, it may not

Saved by the disclaimer :greensmok

Talk me into (out of?) 4.88's

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