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· King Thread De-Railer
2,799 Posts
Discussion Starter · #1 ·
There are many different variations of the Ford 8.8 axle. One of them is best suited for the use in a Jeep and that would be the Explorer (or Mountaineer) 31 spline 8.8. If you have found one off a Aerostar, Mustang, F-150 etc, you should really pass it up and look for a Explorer axle if you wish to retain a similar track width on your Wrangler. Trying to start your build-up with the wrong axle will be frustrating and expensive although you may have picked it up for cheap in the beginning.
Ford 8.8 assembly specs:
Cover bolt 28-38 ft.lbs.
Pinion bearing preload 16-29 in.lbs.
Pinion bearing preload 8-14 in.lbs (used)
Ring gear backlash .008-.015
Ring gear bolt to case 70-85 ft.lbs
Side bearing caps 70-85 ft.lbs.
Explorer 8.8 Measurements:
Weight (complete assembly w/ brakes etc.): 174 lb.
O.D. of tubes: 3.250".
Tube thickness: .250" (some are .188”!)
Ring gear diameter: 8.800".
Ring gear bolts: 7/16" dia. (qty. 10).
Pinion diameter/splines: 1.625 / 30.
Axle shaft/splines: 1.320 / 31.
Rotor thickness (where it mounts to axle is .250").
Overall width 59.625" (the F8.8 is .950" narrower then a TJ Dana 35).
(The F-150 8.8 is drum brake and width WMS to WMS is 65.5”.)
Hole diameter for ABS sensor in top of housing: .811".
Bolt size (U-joint flange to yoke) is: 12 x 1.75 x 30 mm
Centerline of housing to C/L of pinion difference is 3.875" toward the P/S.
Pinion offset: P/S to C/L of Pinion, 27-3/4" (no rotor on axle), D/S to C/L of Pinion, 31-5/8" (no rotor on axle). (this measurement is 2.5" more offset to the P/S then a TJ Dana 35).
Code Capacity Ratio
43 Open 3200 3.08
41 Open 3200 3.27
42 Open 4.10
46 Open 3.73
45 Open 3200 3.55
D4 Limited Slip 3200 3.73
D2 Limited Slip 4.10
L73 Limited Slip 3.73
L - Limited Slip Differential
C - Conventional Differential
How many splines are the axle shafts?
drivers side is 31 spline for 97 & up Mountaineer, 95 & up Explorer, 30-1/2 inch length - 5 X 4.5 inch lug pattern.
passenger side is 31 spline for 97 & up Mountaineer, 95 & up Explorer, 27-5/8 inch length - 5 X 4.5 inch lug pattern
Can I get 35 spline shafts?
Yes, with a little searching I found 28 and 33 splines too. Remeber 8.8 axles are used on many different Ford rigs. Mustangs, Rangers, F150s, Aerostar etc... different axle lengths than the Explorer so if you are looking for aftermarket products make sure you are not looking at something for a Mustang that might not fit an Explorer.
Can I use my drive shaft that I bought for my SYE/Dana 35 set-up? Yes
Is the 8.8 narrower than a Dana 35 rear axle?
Yes but not enough to make a difference when running most aftermarket wheels.1.5" shorter or so. It doesn't matter unless you try running stock rims w/12.5 or wider tires.
Are the 8.8 shafts stronger than Dana 44 shafts?
Yes, also the bearings, pinion and ring gear are also much larger.
Axle shaft Strength and output torque rating by Warn and 4 Wheeler
The axle shaft strength tested by Warn Ind:
F8.8= 6,500 (lb. ft.)
D44= 4,600-5,000 (lb. ft.)
D35C= 4,000-4,300 (lb. ft.)
COT: Continuous output torque rating
MOT: Maximum output torque rating

(Numbers from January edition of Fourwheeler, page 60.)
Dana 35 rear axle COT: 870 MOT: 3480
Dana 44 rear axle COT: 1100 MOT: 4460
Ford 8.8 28spline COT: 1250 MOT: 4600
Ford 8.8 31spline COT: 1360 MOT: 5100
Dana60 semifloat COT: 1500 MOT: 5500]

Will I need that brake proportioning valve from a Rubicon? Probably not

Does the 8.8 offer more ground clearance over the Dana 35 and 44? Not under the differential but the bigger axle tubes lift the rig about 5/8 ".

Is there welding involved? Yes, but the new brackets you put on are much stronger than stock Dana’s. Not a good idea to re use your old Dana 35 brackets

Can I reuse my Dana 35 brackets? Yes, but it is not recomended. The stock Dana 35 brackets are sort of flimsy compared to the beefy aftermarket versions. Some of the brackets available are in fact for Dana 35 axles to replace the weak ones that come factory. Reusing the D-35 brackets is time consuming even if you have the right tools, not a good idea IMO

Should I weld the axle tubes to the cast housing? I would if it had been salvaged from a wrecked rig. If it is new on a crate (in my opinion) don’t bother.

Will my stock sway bar work? Yes, with a minor modification to a passenger side pinion gusset.

Do all 8.8s come with a limited slip? No, read the tag on the housing or remove the cover. 3L73 = 3.73 gears witha "L"imited slip

Where is the gear break for lockers? There is no break. Same locker for 3.73 to 6.14

Do I need a notched cross pin? Yes for 4.56-6.14 to clear ring gear, or notch a gear tooth.

More cross pin info
The 3/4 inch cross pin only fits those rears with the 28 spline count period!
Therefore, the 7/8 inch crosspin is what we are concerned with and it fits Explorer, Mountaineer, F150, and Expedition's with the 8.8 ring gear and 31 spline axles. It also come in those special Mustangs that have the 31 spline axles i.e. Cobra, Steeda, and Rousch.

The axles for Jeep conversion we are keen on are the 96 through 2001 Ford Explorer and Mercury Mountaineer with disc brakes and all that fall into this category with or without limited slip have the 7/8 inch cross pin.

Convert from a 28 to a 31 spline??? Need bigger axle tubes too! The bearing on a 31 spline is much bigger than a 28 spline bearing.

What year ford explorers do I look for as a donor for 31 spline and disc brakes? To get rear disc brakes and 31-spline axle, you need to look for a 1995 to 2001 Explorer or Mountaineer. Earlier years use drum brakes and may be 28-spline. Different vehicles may have the wrong bolt pattern, width, spline count, or brakes. A 2-door Sport Explorer may be a donor past the 2001 cut off. Also, Explorer SportTracs with production dates of August 19, 2002 through June 29, 2005 are equipped with 31-spline axles and rear disc brakes and are exactly what was in the previously listed 95-2001 Explorer. Before Aug 19, 2002, the Sport Tracs were equipped with the smaller 28-spline 8.8 axle shafts and used drum brakes. After June 29, 2005, Sport Tracs were produced with an Independent rear as found on 2002 regular Explorers.* Sport-Trac

What is so great about 8.8? Parts are everywhere, as in axle shafts, covers, brake parts etc..

What's not so great about the 8.8? Weak stock carrier, replace with a carrier type locker like ARB or Detroit (not a lunch box type) this will cure the problem.

Spun axle tubes: Simply weld the tubes into the diff housing before they spin. You are welding to cast steel so now would be the time to ask for a professional's opinion. I have heard of guys tossing the works in a oven before welding, some just go at it cold. Both say their way is right.

Thin stock diff cover: Get some armor.

What kind of locker can I get?

What is the bolt pattern? 5 on 4.5” just like stock TJ/YJ wheels.

Will my Jeep lug nuts fit the 8.8? In most cases, yes.

What do I do with the speed sensor? leave it in place.

How much do they cost? Free to $1500.00 but you can find them new for around $500.00 in their stock form complete disc to disc.

What do I need for a swap into a tj?
Here are some things I used:

-TeraFlex Bracket kit
-U.S. Gears 4.56
-Master install kit (Timken)
-Crane diff cover
-Napa brake line kit P/N 380528 (x2)
-T-hose NAPA P/N 380889
-ZJ E-brake cables (drivers and passenger side)
Mopar P/N 52008904 & 52008905
NAPA P/N 95342 (right) 95347 (left). (not for YJs)
-Driveshaft adapter: Spicer 2-2-1379
-Flange bolts Ford P/N N800594-S100 (x4)
-'03 TJ Rubicon (w/disc) proportioning valve P/N 5083808AA
-3/16" hard brake line about 40" & 18"

HELPFUL SITES be sure to check these out:
Dome & Detour
8.8 Swap
J.E. Towle / DPG Offroad
Chris Overacker / CODE 4x4
4x4 Wire Links
The Ranger Station Tech Library
The Ranger Station Tech Library 2

· King Thread De-Railer
2,799 Posts
Discussion Starter · #2 · (Edited)
From M.O.R.E.-XJ Installation Kit P/N 98600 84-2001 XJ
-XJ E-Brake Cable Kit P/N EB3 Disc Brake F8.8 Only
-Special Yoke P/N 221379 F8.8 to 1310 U-Joint

From Dealership:
-Mopar spring perches
-Tabs for shock mounts
-ZJ ebrake cables from the dealer (for XJ install)
-Flange from spicer dealer $30 (have seen this go from $20-$50)


Stock brake cables won't come off bracket at tub. Pound a deep 13mm socket on the cable end to compress the fingers holding it in place.

Add gear oil through the abs sensor hole at the top. With an 19 degree pinion angle, I just pour three quarts in and call it full.

To replace axle seals, use the end of the removed axle shaft to pry the seal out.

Axle shaft bearings...remove the seal first as above, then slide hammer the bearings out.

Parking brake shoes can make rotor removal a pain after rust sets in, I always machine the inside lip of the rotor (drum section) about 3/8 inch from the edge to the edge about .030 deep so rust won't interfere by dragging on the shoes.
Old parking brake shoes can have the lining come loose from the metal part of the shoe...reglue with two part epoxy if new shoes not readily available...(it's only a parking brake). Parking brake shoes from Ford...$115 set! Autozone...about $20!
^in the quotes i reposted this if the OP has any problem with that. please contact me.
write up came from.[/quote] kits: i

personally liked this kit but its a little bit pricey compared to others.
(will post pics of install next week at some point)
Iron Rock offroads kit

M.O.R.E kit

other info i found on the interwebsss i found these links helpful.

braking issues with the 8.8 Swap

Truss i didn't really look into this but i figured id add it to the thread anyways.
swapping the rear and installing a Truss. ill see if i can find a write up on that.

· Registered
1,608 Posts
Yeah, didn't know TJ's came with the option of an 8.8 :p

Quite frankly, I'm not sure why Austin decided to split up the two categories. What if I put TJ OEM equipment on my YJ? Is that considered OEM or not?
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