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What would gears realy do for me???

K

kenny schmitt

NAXJA Forum User
Location
US
I have a 99xj w/ a 5.5" RE short arm and 33's and some other stuff. I have had this lift in 2 trucks (rebuilt) and have been pushing the 33's with 3.07 gears in both (DD manuals). I have always though about gears and and now i am thinking lockers and gears. lockers are another topic but as for gears im thinking 4.56 ish (may go 35 tho) and doing a rebuild on the 29 spline 8.25 and d30
how much will the gears help mpg, street driving, acceleration......
 
i guess i GOTTA do it. my rear is making a glug lug noise. normal? also how much play?
1)when on jackstands should heel move a little in out and up down? little?
2) should there be much clanking and play when turning wheel back and forth on jackstands? play between wheels in the gears?
3) list of parts (do it once) aside from gears and lockers? and tools needed to do this on my xj in my drivway

8.25 29 spline btw
 
Call up a big gear dealer and they will set you up. most of there prices are the same. Where you really have to shop around is with the install.

I would recommend 4.88's.
 
First off, no offense but if you don't know the answer to those questions you aren't ready to install gears.

Define "glug lug"... Probably not normal. How much play in what?!

1. By heel I assume you mean 'wheel'. I'm not sure which wheel you are refering to but neither wheel should move up and down, in and out. At all. Ever.

2. If there is play between the wheels then most likely you need to replace tie rod ends. There should be very little clanking.

3. A mechanic. (Quite a few tools) Read this. If all of this doesn't make perfect sense then I would suggest you have someone do it for you.

http://www.pirate4x4.com/articles/tech/billavista/Gear_Setup
 
well they will make the truck feel more powerful... they will make the truck do better on the highway and some people say if you pick gears that give you 3,000 - 3,500 RPM at highway cruising speeds that you will get better MPG (at least that is what I hear on the 4.0

also keep in mind that the stock is around 27.5" tall

a 33" tall tire is also wider and weighs a a lot more

so at the very least the new tire is 5.5" taller than stock, or about 20%, plus the added weight... 20% deeper gears would be like 4.26:1 but I don't think they make that, lol they make 4.10 but that is not deep enough, however a 4.56 should do nicely, or even a 4.88 if you want a little more powerful feel

that being said I put 285/75/16 (32.5 x 11.25 x 16) on mine with stock gears (3.55:1) and it does pretty good, feels good in town, but it drops out of overdrive going up hills on the highway, I plan to do 4:88 gears some time in the next 12 months 4.88s should give me around a 3,400-3,700 rpm highway RPM
 
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4:11 or 4:56 .. will increase ur fuel milage and will be alot easier to take off from a stop almost just let the clutch out and creep;.. with gear u will be able to creep to almost a complete stop (1-2)mph without the car shuttering the gear it will take ur top speed down and mess up your speedo . but that can be fixed with a new gear
 
lowrange2 said:
Dramatically! I don't have numbers to back up my opinion but it makes a MAJOR difference! Imagine doubling the power of the engine...
Click to expand...


I often hear that turning the 4.0 at high RPM's inprove MPG. My experiance is just the opposite. Anything above 3,000 RPM causes a dramatic decrease in milage. I guess the experiance of the Renix users is different to mine. :dunno:

Changing gears was the the best mod I have done to the XJ. I am using 4:10 since I am not going to use larger than 31" tires, does 90% of highway driving and no hardcore wheeling. The 4.0 does 2550 RPM at 70 MPH with 30" tires. I will to go to 31" tires when the present set wear out. Going to 31" should drop the RPM by 100 RPM to 150 RPM at highway speed.
 
31's and 3.55's were just about perfect in my 4.0/5 spd MJ for the higway. I consistenly got better than 20 highway cruising. For 33's I'd do 4.10's or 4.56's if you DD it. If it's a trail rig, the deeper the better. Your clutch will not hate you so much.
 
CLUTCH LIFE BABY. Even on the pavement. You got to be slipping that clutch a lot more to get them 33 rolling. Start offing much and you will SOON need a new clutch.
With a stick and 33 and light offing 456 will do fine
For 35 and or heavy offing 488
This isn't even talking about how much more fun a stick is to drive when well geared.
Also easier on the coolant system.
Brakes! yes brakes. Bigger tire are harder to stop to. But with better gearing the engines braking effort is also multiply. Often making so called brake upgrade unneeded.
Sorry flush-o-matic drivers but it don't help you near as much. Do to the slush converter slippage killing off much of the engines braking force.
 
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youll gain some clutch life for sure... on and off road.

use the calculators online to see where you want to be in your RPM range. (if you have the AX-15, your final gear is .79. thats the only one i know off hand). 4.10s and 33s will put you right at stock ratio, 4.56 will be over geared. 500 more RPMs may be a little much for a DD. your tastes though.
 
From what lots of members who have changed gears, if you even THINK about going up to a larger tire, go with a gear step up.
For 33's I would at LEAST go 4.56, Your highway mpg may take a little hit, but city should be up.
I need new tires soon, and didnt want to go with large rthan 30" tires, but I can get a good deal on 4.10s so I MAY get some 31's. I mostly DD mine, so I don't want to take a big hit in the highway economy.
 
well firs im sorry for my response about that glug lug thing. i was sound asleep seconds later....

When moving slow like backing into a spot or after the clutch engages i hear a noise coming from the rear floorish area. it has a lug glug sound to it and seems to be the rear. just did the shoes drums and springs n things but dont think its that(happened before).

Also the play i as talking about is in the rear only. with the rear on jack stands you can feel a small abount of play pulling outward
also w/ the rear on stands and turning the wheel forward and backward there is play between the other wheel. i know some is fine but it almost seems like a lot.

and about the original question.... NO MATTER what gearing i go with (anybody's recommendation) prob 4.56 i will be looking at much better mpg than i get now?
and although a dd i like to wheel the hell out of it when i can
 
I was running 31's on 3.55's, it sucked.

I went to 32's, and it sucked even more. Mileage around town was bad, going up hills was terrible, and wheeling... it offered no engine braking.

Went to 4.56, it's freaking awesome. Mileage is better overall. I seemed to lose mpg on strictly flat ground, but when you add in hills, mpg is much better.

And I can cruise up steep hills in 4th gear. (Automatic)

I rev at 2500 at 65 mph. It will go down a bit, and should be quieter when I go to 33's.
 
From the discussions I've had with several folks around here and reading a lot, I've seen most people suggest going with 4.56's with 33's (Or 305/70/16 in my case). I'm still not quite sure I'd like to DD my rig on the highway 25+ miles one way to work at 2700+ RPM's as opposed to 2450 RPM's with 4.10 gearing. I mean, it doesn't seem like that much of a difference but will the jump from 4.10's to 4.56 make such a big difference in highway/city driving? Plus, my current engine has over 220k on the clock and any unnecessary abuse I put on it probably isn't advisable. :p I know for sure the 4.56's are better on the trail...I'm more concerned with the DD duties/milage etc..

Oh, for those wondering, I used http://www.grimmjeeper.com/gears.html to figure out what gear ratios and tire sizes equate to in RPM etc (Thanks Frank!)
 
ericfx1984 said:
that being said I put 285/75/16 (32.5 x 11.25 x 16) on mine with stock gears (3.55:1) and it does pretty good, feels good in town, but it drops out of overdrive going up hills on the highway, I plan to do 4:88 gears some time in the next 12 months 4.88s should give me around a 3,400-3,700 rpm highway RPM
Click to expand...

What? do you have a 3 speed? It would give you more like 2,400rpm at 65 if you have OD. If you wanted to really spin greater than 3,000rpms anyway it would be easiest just to keep it in 3rd lol. I don't think having gears that low for 3000+ in OD would help getting up to speed either.
Though I shutter at the idea of spinning that fast.
I have 31s 3.55s so 65 is around 1500, 75 2000, 85 2500 (yea I was cruising on a nice open stretch the other day on unbalanced tires and crap suspension but I think after the OMEs I just got and balancing + replaced bad o2 it should do nice) . And it seems to do great especially 45-55 it just pulls in the low rpm range like it wants to take off. I am interested in 4.10s though since I was planning to swap the front axle (4cyl) and putting a rebuilt trac lok in the 8.8 (find some 4.10s while its out) so the extra low end would be cool for smokin the imports lol and I'd be cruising about 1900rpms (stock ratio) 65, 2400rpm 75.
Edit: Also was getting 20mpg at some point (just started driving again recently) 87 4.0 aw4 (88 motor) CAI, Cat delete, dynomax muffler(great non-look at me muffler), advanced timing
 
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