Replacing Rear End

Nate882004 · Apr 13, 2014

the rear end in my 96 FSB appears to need to be replaced. If this does turn out to be the case, any suggestions on replacing or rebuilding it?

Any suggested upgrades? or Should I just stay with stock?

All comments welcome.

Nate882004 · Apr 13, 2014

Rear end is currently stock with stock 351cc engine and stock auto tranny. Truck has a 2.5" suspension lift and currently has 31" tires but I plan to switch to 33" soon. It's a daily driver that I like to play with on occasion.

miesk5 · Apr 14, 2014

yo Nate;

WELCOME!

fyi,

96 Bronco-F-Series Workshop Manual by Ford

https://www.motorcraftservice.com/pubs/content/~WSTJ/~MUS~LEN/21/STJLEFT.HTM

see either;

Section 05-02G: Axle, Integral Carrier, 8.8-Inch Ring Gear or

Section 05-02H: Differential, Traction-Lok Limited Slip, 8.8-Inch Ring Gear

Rebuild in a 95
Source: by sackman9975 (Scott

"...Ford built our Broncos & other 4x4 trucks & vans with a numerically lower front gear ratio in the front Dana 44 than the rear so that off-road steering is enhanced. A Bronco built with 3.55 rear ratio would have a 3.54 ration in the front Dana 44; or; 3.08 in the 8.8 & 3.07 in the Dana 44; or 4.11 in the 8.8 & 4.10 in the Dana 44, etc..."; Following was in my MS WORD Notes and the source, Randy's Ring & Pinion has removed it from their current web site; The gear ratio in the front of a four wheel drive has to be different from the front so the front wheels will pull more. There have been many different ratio combinations used in four-wheel drive vehicles, but not so that the front will pull more. Gear manufactures use different ratios for many different reasons. Some of those reasons are: strength, gear life, noise (or lack of it), geometric constraints, or simply because of the tooling they have available. I have seen Ford use a 3.50 ratio in the rear with a 3.54 in the front, or a 4.11 in the rear with a 4.09 in the front. As long as the front and rear ratios are within 1%, the vehicle works just fine on the road, and can even be as different as 2% for off-road use with no side effects. point difference in ratio is equal to 1%. To find the percentage difference in ratios it is necessary to divide, not subtract. In order to find the difference, divide one ratio by the other and look at the numbers to the right of the decimal point to see how far they vary from 1.00. For example: 3.54 ÷ 3.50 = 1.01, or 1%, not 4% different. And likewise 4.11 ÷ 4.09 = 1.005, or only a 1/2% difference. These differences are about the same as a 1/3" variation in front to rear tire height, which probably happens more often than we realize. A difference in the ratio will damage the transfer case. Any extreme difference in front and rear ratios or front and rear tire height will put undue force on the drive train. However, any difference will put strain on all parts of the drivetrain. The forces generated from the difference have to travel through the axle assemblies and the driveshafts to get to the transfer case. These excessive forces can just as easily break a front u-joint or rear spider gear as well as parts in the transfer case.
Source: by miesk5 at Ford Bronco Zone Forums

Tire & Lift Guide for Larger Tires

http://img1.photobucket.com/albums/1003/gearrat/tire_guide.jpg

by John R (azrockrat, GEARRAT, Christine)

Gear Ratio Guide for Large tires and RPM chart

http://web.archive.org/web/20111117131542/http://www.broncocity.com/resources.htm

Tire Circumference Differences; "...The ability of four-wheel drive and all-wheel drive vehicles to divide the engine's horsepower between its four tires is especially useful on loose or slippery surfaces such as sand and dirt, as well as on wet, icy or snow-covered roads. However it's important to remember that in order to transfer this extra power, the four-wheel drive and all-wheel drive vehicle's driveline mechanically connects the tires so they work in unison. Four-wheel drive and all-wheel drive vehicles are equipped with additional differentials and/or viscous couplings that are designed to allow momentary differences in wheel speeds when the vehicle turns a corner or temporarily spins a tire. However, if the differentials or viscous couplings are forced to operate 100% of the time because of mismatched tires, they will experience excessive heat and unwarranted wear until they fail. This necessitates that four-wheel drive and all-wheel drive vehicles use tires that are very closely matched. This is because different diameter tires roll a different number of times each mile as a result of the variations in their circumferences. Tire diameter variations can be caused by accidentally using different sized tires, tires with different tread designs, tires made by different manufacturers, different inflation pressures or even tires worn to different tread depths. As an example of different tire diameters resulting from tires worn to different tread depths, we'll compare two 225/45R17-sized tires, a new tire with its original tread depth of 10/32-inch and a second tire worn to 8/32-inch of remaining tread depth. The new 225/45R17-sized tire has a calculated diameter of 24.97", a circumference of 78.44" and will roll 835 times each mile. The same tire worn to 8/32-inch of remaining tread depth is calculated to be 1/8" shorter with a diameter of 24.84", have a circumference of 78.04" and will roll 839 times per mile. While the difference of 1/8" in overall diameter doesn't seem excessive, the resulting 4 revolutions per mile difference can place a continuous strain on the tires and vehicle's driveline. Obviously, the greater the difference in the tires' circumferences, the greater the resulting strain. This makes maintaining the vehicle manufacturer's recommended tire inflation pressures and using "matched" tires on all wheel positions necessary procedures to reduce strain on the vehicle's driveline. Using "matched" tires means all four tires are the same brand, design and tread depth. Mixing tire brands, tread designs and tread depths may cause components in the vehicle's driveline to fail. Mismatched tires or using improper inflation pressures for all-wheel drive and four-wheel drive vehicles can also result in immediate drivability problems. Some Control Trac equipped vehicles in 4Auto mode may exhibit a shutter on acceleration and/or a noise from the front driveline and transfer case while driving. Some all-wheel drive and four-wheel drive vehicles may exhibit axle windup or binding while driving. Some four-wheel drive vehicles (manual or electronic shift) with a two-wheel drive mode may refuse to shift "on the fly" into 4x4 Auto or 4x4 High at highway speeds..." read more, esp. Matching Tires By Shaving Them to Maintain Equivalent Tire Tread
Source: by tirerack.com

Nate882004 · Jul 26, 2023

I know this is old but...

So, this Bronco I hit some black ice, went over the side of a bridge, dropped 20' into a frozen creek below, and was totaled. Roads had all cleared but this was a low shaded area and caught me off guard. This really hurt my feelings losing this truck.

I bought another 96 Bronco EB a few years ago and the rear end is now going out, confirmed. Its been recommended to replace it rather than repair. Now I'm back here looking at this old post. Thanks for the resources.

miesk5 · Jul 27, 2023

Yo Nate,
Sorry to hear about you going through black ice and losing your 96, but at least you weren't injured, I hope!
Be Well Nate!
Al

Nate882004 · Aug 25, 2023

So I am tackling this rear rebuild on my own with no experience. I really appreciate the recourses. They've helped. I am live streaming it on YT if anyone is interested in watching.

https://www.youtube.com/live/HKKsTrnlV10?si=41MuucflXmeee0qb

I know its clumsy and dangerous, but I am learning.

paul rondelli · Aug 28, 2023

The 8.8 is pretty stout. probably a great time to re-gear. 35" inch tires and a 6 inch lift is about the max for a TTB. My 1993 has this set up with 4:56 gears .... very nice.

You might as well go 2005 (or newer) Super duty solid front axle and the sterling 10.25 for a rear end. The ole 1 ton upgrade.

You won't ever have to worry about the axels being the weak link in that drive train.

stumped · Aug 29, 2023

Nate882004 said:
the rear end in my 96 FSB appears to need to be replaced. If this does turn out to be the case, any suggestions on replacing or rebuilding it?

Any suggested upgrades? or Should I just stay with stock?

All comments welcome.

I had the stock 3.54 rear/front gearing (4 wheel drive) and it great for gas mileage and reasonable power. I switched to the next lower gearing because I pull a heavy cargo trailer from time to time and it gives a little more torque. I have the 96 Bronk 302. I am selling the ring gear 8.50 size 10 bolt if you know someone that is interested. Its in good condition with 127K miles on it.

Motech · Aug 29, 2023

I can only concur with the upgrades @paul rondelli recommended. That 1-ton setup will not only be bulletproof, it's also not that difficult to adapt and will provide a massive, envy-stoking level of badassery everywhere you go.

Replacing Rear End

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