Regearing 1991XLT from 3.55 to 3.73

[beckhm1991]

I have a 1991 XLT 4x4 with 3.55 gear ratios. I put a larger tire on the vehicle last year and am in need of lower gears, not enough low-end torque to get up the hills around Seattle. I have opted to purchase a new rear end with 3.73's and limited slip, I have no problem swapping out the rear axle, but have not had the opportunity to do any front end work on the X yet, other than bearings, brakes, manual hub conversion. I don't fully understand what it is I need to get to swap out the front gears, do I need to be looking for a new carrier, gear set, etc. I want to go with the most cost effective option, but need some guidance from someone who has done a gear change themselves. Any advice would be great. I have found a low mileage 3.73 rear with LSD for $300 and a front carrier for $150...anything else I might need?? Appreciate the help

 

[DeRocha]

What size tire are you running or planning to run? 3.73s will be a small improvement over 3.55s. I went from 3.27s to 4.10s (33s tires) and it was an improvement (but nothing earth shattering). Basically the 4.10s with 33s put the engine power slightly better than stock. For more power and low end torque I would recommend 4.56s.. Basically If you're going to do all the work swapping out the axles and front carrier I would jump to 4.10s or 4.56s.

IMO 3.73s wouldn't justify the expense and work involved for a minor improvement over what you have now..

 

[JDraper]

If you have never set up gears before, you would be best to swap out the complete axle assemblies (Both front and rear) nstead of trying to install new ring and pinion gears. Setting up the gears properly takes a lot of patience, know-how, and the proper set of tools. It's not something for an inexperienced shade tree mechanic. You can't just bolt new gears in and go. You have to set up pre-load, backlash, pinion to ring gear tooth depth, etc.

 

[wood1]

You will probably be disappointed in the change from 3.55 to 3.73. I would be surprised if you could tell the difference in the two ratios by seat of the pants feel.

I swapped out a set of 2.73 for 3.55 in my mustang years ago and that was alright, nothing earth shattering though.

IMO you need at least 4.10 to get an improvement.

C.

 

[MountaineerGreen]

IMO 3.73s wouldn't justify the expense and work involved for a minor improvement over what you have now..

My thoughts exactly. 4.10s or lower or isn't really worth the effort.

 

[beckhm1991]

If you have never set up gears before, you would be best to swap out the complete axle assemblies (Both front and rear) nstead of trying to install new ring and pinion gears.

I am definately going to be swapping out the complete assemblies if I do go ahead with this project...say next spring, but I am going to be tracking down the parts in the next few months. I have the patience but not the tools to setup the gears, and the rig is a daily driver, can't afford to do it the wrong way.

With that said, I did some more research last night, read axle 101 threads, and am now convinced that a 3.55 to 3.73 swap would be worth about as much as switching from Old Navy to GAP and expecting an immediate quality improvement, I think if I am going to do it right I need ot switch to Banana Republic...AKA 4.10 or 4.56. My only concern right now is that I do alot of highway driving back and forth from Seattle to Spokane...about 300 miles, and want to still be able ot make that trip on one tank of gas...each way..ha. that said, I am currently running a 30x9.5 tire and would likle to upgrade to a 31 or 32 at some point, would I still get good low end torque over stock running 4.10's with a 31 or 32" tire? I think a 4.56 is a bit beyond my needs, but maybe it isn't, anyone from Seattle want to offer me a test drive and convince me otherwise.

While we are here I might as well ask about rear diff's. Like I said I stick to the highways for the most part but do alot of winter snow driving, and am going ot be purchasing a small trailer to pull behind the X for tools...maybe 1500 lbs max load, what type of diff would ya'll suggest...trac-lok?? some sort of locker?? I have done some HW but don't quite know what would be ideal...biggest bang for the buck.