4x4Wire TrailTalk

Gear Questions

Posted By: josephelk

Gear Questions - 12/21/06 02:53 AM

I have an 89YJ that I have lifted 3.5" with 33" tires and just installed the 4.0 engine swap and all works great. I would like to install some new gears, But have been told several gears will work 4.11- 456 are the main two? Because this is my daily driver I would like to install the right gears that work the best for performance and mileage, does anyone have an opinion on this that could help me? I have a Dana 35 rear & Dana 30 front and should I match the front gears with the rear or could I do the rear now and front later or am I going to have problems with 411 or 456 in the rear and stock gears in the front?

I also just received my Posi-lok system to do away with the old stock vacuum 4 x 4 engagement system. Has anyone heard any good or bad things about the Posi-Lok?


Posted By: BigJim

Re: Gear Questions - 12/21/06 05:41 AM

Oh NO! Please don't put the gears in one at a time.. If I did that I would pull the shifter out of the transfer case or the front driveshaft.. I'd make it where there was NO WAY to engage the front wheels!
With never going higher than 33's using a 3:73 should work fine for the best milage. If around home is hilly maybe the 4:11.. But I think the 4:56 is a bit low for that engine and only 33's.
The posi-loc is a good thing to have unless you drive over the top of a lot of heavy offroad brush and small trees.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />
Posted By: Classic_City_Offroad

Re: Gear Questions - 12/21/06 03:48 PM

Big Jim is right. You have to re-gear the front and rear axles at the same time. I would run 4.11's with your engine and tire size. You would be fine with 3.73's but I think you will still be looking for more low end juice with that ratio.

Classic City Offroad
Posted By: superdawg

Re: Gear Questions - 12/21/06 05:25 PM

Flad landers, sheesh.
Posi lock indicates that your wheeling will be at least serious enough that you can't afford to not have 4x. How into jeeps and jeeping a given person is, is how I answer this question.
If you are sold on the virtues of jeeps and wheeling, 35" tires are next with lockers an axle swaps not far behind.

4.56 or even 4.88 is just fine with 33s assuming a 5 speed
manual tranny, if automatic 4.10 or 4.56.

Forget 3.73.
You have mountains to drive, snow to wheel (snow we have here now 24") get gears that not only suit the imediate need but future needs as well.

Posted By: BobRowe

Re: Gear Questions - 12/21/06 06:35 PM

I think you should go with the 4.11 gears rather than the 4.56 gears. I have the 4.56 gears in my trail-dedicated CJ7. Even with 35" tires, the gearing is too low for me to travel any considerable distance on the highway -- rpms are just too high at 60-65 mph. Yours would be even worse with 33" tires, especially since you say that it's a daily driver.

You could probably get away with 3.73 gears, but I think you'd be happier with the 4.11 geaars once you get off of the pavement.

Personally, I would never drive a 4x4 that had different gear ratios in the front and rar axles. That's a MAJOR screw-up just waiting to happen!
Posted By: josephelk

Re: Gear Questions - 12/22/06 02:21 AM

Thanks for the responses,

I think I will go with the 4.11 front and rear. What manufacture of gears is the best and what manufacture should I stay away from?

IĎve never installed gears before but I pickup on things pretty quick and I have my service manuals that I purchased when I changed out my 258 engine for the 4.0. Is this something I could do myself or should I take it in and have them installed?

Thanks again for the excellent feed back.
Posted By: valleycat

Re: Gear Questions - 12/22/06 03:44 AM

I would just get it done by a pro unless it's something you really want to learn how to do. You will need someone that can teach you and the special tools required to do gear installs.
Posted By: BobRowe

Re: Gear Questions - 12/22/06 05:55 AM

Richmond gears have always worked good for me. But any name brand should do fine.
Posted By: crumy

Re: Gear Questions - 12/22/06 08:03 AM

I got a 2006 Rubicon . I am getting a 5.5 RE lift and am trying to decide whether or not to go with 33s or 35s. Any opinions...?? I was worried about the 35s being to big for everyday driving.
Posted By: josephelk

Re: Gear Questions - 12/23/06 12:01 AM

I think I will have someone else do the gears. After the engine swap I did on my Jeep I think I will take about a year break from working on it? Ya right, I will get my gears and try them out and end up breaking something. But thatís what it's all about, Build it and break it sometimes.

Thanks again for all the good advice.
Posted By: Anonymous

Re: Gear Questions - 12/25/06 03:39 AM

before you go worrying 'bout anything else......REPLACE THE 35C WITH A 44!
Posted By: josephelk

Re: Gear Questions - 12/27/06 04:54 AM

I was thinking about a 44 or a Ford 8.8? Not sure which way to go with that? I have heard the Ford 8.8 is the cheapest and I would get to upgrade to disc brake in the rear. Anyone ever done this conversion on and 89YJ?

Posted By: magsnubby

Re: Gear Questions - 12/27/06 09:42 PM

Check out:

Posted By: superdawg

Re: Gear Questions - 12/29/06 02:58 PM

Overdrive tranny? 5 speed? go with 4.56 and look at the facts, a three speed auto vs a 5 speed manual?

3 speed auto: 4.10 with 33" tires.
5 speed manual: 4.56 with 33 or 35" tires.
For the last 6 years...
I install, on average 5 gear sets a week almost all in jeeps or custom axles to be swapped into jeeps, to date I have never had any customer say to me..."those 4.56 gears are too low, I wish I had 4.10s"ROFLOL. However, I have heard from folks who insisted that I install 4.10s say "god I wish I had listened and had you install 4.56 or even 4.88s.
Two or three gear sets a month for the 10 years prior to that.

If you listen to one fellow with one jeep who suggests to run simply what they are running in their own rig is not doing the smart thing.

You are not creating "crawl ratio" by changing from 3.54 (example) TO 4.88, if the tires went from oe to 33 or 35s.
What you are doing is getting the gear to cam and engine rpms all back matched where they are close to stock performance. Tire height is not the only factor in determining ratio, rolling resistance, air drag and weight are factors also. So if the best gear for 33x12.5 tire and oe engine is a 4.10 add the other factors and 4.56 looks much better. One other factor is "the bug" once you wheel with 33s the 35s are not to far away. Another reason to go one step past the "ideal" ratio.

Posted By: josephelk

Re: Gear Questions - 12/30/06 10:59 PM

Thanks for the responses,

I'm looking a weighing all my options for the gears that I'm going to install in my Jeep. Iím asking a lot of fellow four wheelers that have already gone through the trial and error of using many different gear setups. Remember this is still going to be a daily driver and it will see freeway use every day (about 16 miles round trip to work and back).

Youíre right; the one thing I donít want is to get a gear setup that Iím not completely happy with? If I go with a 4.56 setup is this going to max out my jeep around 65 to 70 MPH? (Personally the freeways that I drive are so grooved from traffic that 60 MPH in my jeep now is scary) and what is it going to do with my gas mileage? If I drop one mile per gallon or so I could live with that, but if we are talking 3-5 miles per gallon then I probably would sacrifice the 4.56 for 4.11?

Anyone no how to figure the miles per-gallon with gearing?


Posted By: BigJim

Re: Gear Questions - 12/31/06 12:01 AM

Joe you need to remember lower RPM's don't mean better milage! If you are happy with your milage now.. then you need to keep the rpm's after the gear change to what you have now or MORE! Since the tires will be harder to spin you will need a few more R's to roll em.
The most common problem I see with installing larger tires is the engine lugs and a lower tranny gear is needed to simply get around town. So you run around in 4th and never see 5th again.
When going up to HUGE meats many more R's will be needed to keep the same or equal "feel" to the ride.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />
Posted By: josephelk

Re: Gear Questions - 12/31/06 10:54 PM

This might be one of those stupid questions but I will ask it anyway? If I put a Ford 8.8 with 4.10 gears in the rear of my 89YJ and keep my DANA 30 front and install 4.11 am I going to have issues? Or are they close enough to matching that I will wonít have problems.

Please don't everyone heckle me at once, take your turns.
Posted By: BigJim

Re: Gear Questions - 12/31/06 11:12 PM

Good choice...do it!
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />
Posted By: oldgreen

Re: Gear Questions - 01/01/07 01:46 AM

Just a personal note, I,ve got an 84 CJ7 that used to have the 258 in it with 4.10,s and a 3 speed TF999 auto running 35 BFG,s. On the highway it would rev at 60mph to 2400rpm. Against a headwind anything faster than 60 was impossible and it was always floored which doesn,t do much for mileage. Off road required low range in sand or rock just to be able to drive around. I have now installed a 304 V8 and expect the extra torque of the 50 cubic inch bigger motor to help a bit. Seriously consider the 4.56,s if you want to run 35,s.
Posted By: josephelk

Re: Gear Questions - 01/01/07 02:03 AM


In Vancouver someone is party out a 1996 Explorer with a 302 engine 8.8 rear end and we cannot match any numbers on the housing to find out what gears are in it. The VIN is 1FM0U35T5TUD31890, other numbers on the axle area S619A-R and 73886E03 if this is 4.10 Gearing I would buy it. How do I find out what the gearing is?
Posted By: josephelk

Re: Gear Questions - 01/01/07 02:09 AM

Thanks Oldgreen and Bigjim,

I have 33 x 10.5 tires on my Jeep and I will not go any taller maybe wider at a later date but not ant taller. The main four wheeling I do is in Mud and snow around Vancouver, WA. Do you think the 4.10 will be ok for that tire size?
Posted By: BigJim

Re: Gear Questions - 01/01/07 03:03 AM

Joe The -R is suspicious to me... Ford uses a R to indicate their locker in the 8.8.
I would spin one wheel and count the revs of the driveshaft to find out for sure.
Look inside the drivers door post for the axel code. If it is in there post it here and I will tell you what was shipped in that thing.
The codes are availabel all over the net.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />
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