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Report: 1999 Ford Explorer v6 Installed Torsen differentials Bilstein shocks


January 22, 2011
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City, State
Whitefish, Montana
Year, Model & Trim Level
I wanted to share my experience with upgrades I recently made to my 1999 V6
Ford Eddie Bower Explorer. I got stuck in the snow recently and only two wheels
turned - the left front and the right rear. This did not seem like "true" 4wd to me.

Up to this point, the vehicle was completely stock and unmodified other than
usual maintenance items (brake pads, tires, etc) with 120,000 miles. The tires
are 265/70-16 Goodyear Fortera TripleTred Highway All-Season.

After reading much on this forum, I became interested in the Torsen differentials.
Ranger Rick (Rick Barnes) was very helpful and patient in answering the many
questions I had about the various Torsen differentials and my specific application.

The front differential was the standard "open" Dana-35 Ford Explorer unit.

The rear differential was the Ford "traction-lock" unit. The clutches were
completely burned out - I could rotate both wheels by hand in opposite rotation
with virtually no effort, and examination of the old differential confirmed the
clutches were completely "gone". It was probably worse than an open diff in
terms of getting power to the ground.

I purchased the 975420-0207B Dana-35 T2 from the Torsen on-line store, and
the Ford M-4204-T31H Ford 8.8 T2R from my local Ford dealer.

The T2R has a higher torque bias ratio than the M-4204-T31 T2. The higher TBR
allows the transfer of more available torque to the wheel that can better use it.

Rick felt that in a heavy vehicle like the Explorer, the higher TBR in the rear
would work well even though the front Dana-35 T2 has a lower TBR.

Installation of the front differential was relatively easy; you can get a bearing
shim pack from Ford which made centering the differential easy.

Installation of the rear differential was a pain in the rear - the shims are fairly
thick and you have to buy them individually.

The T2 diffs have slots cut in them that allow you to use a standard bearing
puller to remove the bearings to change shims without damaging the bearings.
The Ford diffs do not and you have to destroy the bearings to remove them.

I used Ford 75w-140 Synthetic oil in both differentials without any XL-3 /
C8AZ-19B546-A friction modifier. Ford also sells a small plate that attaches to the
differential cover bolts that reads "Use 75w-140 synthetic oil only".

I added the Ford rear axle damper brackets, and installed Bilstein shocks at the
front and at the rear axle damper. The rear axle shocks are the auto adjusting
air shocks so I left them "as is".

I replaced the front upper and lower control arms with MOOG units which have
provisions for a grease zerk fitting.

The results are nothing less than amazing. It is a totally different vehicle in the
snow and ice. I was able to do "donuts" in 2-foot deep snow where before it
would have gotten stuck. There were times when driving on ice where I could tell
one wheel was just beginning to lose traction, and then like magic it did not.

Where others were driving 5mph and losing control, I was able to drive 25mph
comfortably with a full load with no hint of control issues - even on icy
surfaces with the outside temperature 19-degrees on California Highway 120
to Yosemite over the New Years holiday.

One other interesting note - when under any throttle at all when letting go of the
steering wheel after a turn, the wheel practically jumps to center - in 4wd mode
you have to use some effort when under throttle to keep the wheel from going
back to center. I don't consider this a "bad" thing at all - the vehicle now seems
stable at speeds under conditions I would have never tried before. The vehicle
seemed "rock solid" at all times now.

I cannot more highly recommend the Torsen differentials. Anyone considering
upgrading their drivetrain should seriously consider Torsen differentials.

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Thanks for the back story, and welcome.

How much was the front diff? I've installed two of the rear 8.8's, and they work great.

The total cost for the Dana-35 Explorer front differential from's online shop delivered was $530.00.

Thanks, and that isn't awful. The first estimates were well over $1k, I'm glad they finally brought it out. I had a spare front diff rebuilt with my front suspension, thinking they were not going to produce it. Now I can put that on my long list, maybe down the line to do. Regards,

Truth be told, the '99 Explorer is my wifes vehicle. My ride is a 2003 Ranger
FX4 Level-II which has the (only preloaded) Torsen T2 factory installed in
the rear axle assembly. One of the reasons I decided to upgrade the '99 Explorer
with Torsen differentials is the performance from the Torsen T2 in my Ranger. I
was so impressed with the improvement in my wifes Explorer, that I purchased
another Dana-35 T2 Torsen differential, which is being installed in my Ranger
this Monday along with a pair of MOOG upper and lower control arms. The
Ranger has 31X10.5R15 Goodyear Wrangler SilentArmor On-/Off-Road All-Terrain
tires which IMHO are far superior to the stock BFGoodrich All-Terrain KOs.

While the FX4 Level-II shares a lot of components with the Explorer Sport
Track (same front disc brakes, same rear drum brakes, etc) this Ranger comes
with "staggered" rear shock absorbers, the drivers side trailing the rear axle and
the passengers side leading the rear axle. Even though the Ranger 8.8 rear axle
has the mounting tabs for the Explorer axle damper inboard mounting bracket,
the leading shock on the passengers side is right in the way of where the frame
bracket for the axle damper would mount. This precludes installing the Explorer
axle damper assembly on this Ranger. I guess the staggered rear shocks were
put there by Ford to make up for "axle hop" on such a vehicle with so little weight
on the rear compared with an Explorer, which has trailing shock absorbers on
both the drivers and passengers side.

Good stuff. Where is the frame mount for the odd shock on the Ranger? If the mount is in the same location, you could upgrade to the V8 bar(you called it the axle damper), by swapping the lower shock mount bracket.

I loved the Torsen rear diff, when I installed in in the 2004 Winter. That alone with Blizzak tires would almost not spin the tires on fresh snow. AWD and 4WD is very good, but the available tire traction and differentials are critical.

For work I drive a POS mail truck with recap tires. In just snow it's treacherous, but I do see a few 4WD trucks spinning along with two tires. I'm more worried about stopping and steering, tires are the biggest key there. Regards,

The frame mounting bracket for the passengers side leading shock is riveted to
the inside of the frame rail in the same place where you would mount the axle
damper shock mounting bracket. It's similar to the drivers side except for the

It reminds me very much of the staggered shock setup Ford installed on the '60s
and '70s muscle cars, like the 428/429 mustang/cougar/fairlane/torino, the
Boss 302/351/429, and others where the axle leave spring u-bolt retained plate
has a "tab" for the lower shock stud, and the shock plates are stamped with a "L"
and "R" so you can tell which one goes on which side of the axle, only on those
cars the shocks mount more "staight up" into a cross member that connects
the left and right subframes, and are accessed via openings under the rear seat,
whereas on the Ranger the upper shock mounts to a bracket riveted to the inside
of the frame rail.

I still wonder if you could mount the odd shock to the upper frame in just the same place as an Explorer. If you would prefer the V8 axle damper bars, I'd go that route. But maybe you don't need it that way, it would depend on the engine power.

So are you telling us that you can install a torsen D-35 in the front of your Level II without having to reset set up gears?

My 04 Level II has a bad ball joint, so when I fix it I was considering the same upgrade. Let us know about that upgrade too.

Used the same ring gear. Used new ring gear bolts to mount the old ring gear
to the new differential. Measured the backlash of the stock unit before taking it
apart, and then set the backlash of the new unit to be as close as possible to the
original unit by adjusting the shims that go between the differential carrier
housing and the bearings. On the Ford diff you have to destroy the bearings
to remove them, on the Torsen diff there are small cutouts behind the area where
the bearings mount that allow you to use a puller so you dont have to destroy
the bearings to remove them.

I'll try and take some pictures and post them.

As for the V8 track bar, that is an interesting idea I did not know about. I have
a friend who owns a 2000 Explorer with the 5.0 AWD so I'm going to look at that
to see how the track bar mounts...

Some additional information (I have pictures which I will try and upload).
The ranger FX4-II shock absorber axle brackets are welded to the axle tubes,
and the shock absorbers go almost straight up to a bracket that is riveted
to the inside of the frame. I have not looked at a "regular" Ranger but on
my '03 FX4-II the shocks are staggered. The frame rails are closer together
than on an explorer - even if the passengers side shock was trailing instead
of leading, there would be no way to mount the axle damper shock from the
explorer because of the frame rail distance difference between the explorer
and the ranger.

Ah yes, the frame isn't identical in the back. I recall it's the same up front, but I forgot that the back changes. We do what we can.

For your pictures, they need to be 600x800 or smaller. You just browse for them on your PC with the Manage Attachments button, on the full editor page. Regards,


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Pictures of Ford and Torsen differentials

Attached are three images - the stock Ford differential installed,
the Torsen differential installed showing backlash of .004, and
the Ford and Torsen differentials shown side-by-side.

The part numbers are:

Torsen 975420-0207B Dana-35 T2 - $500.00
Ford F57Z-31222-AA Ring/Pinion Retaining Bolt Kit - $16.41
Ford B7A-4221-A Carrier Bearing Cone and Roller Assembly - $27.97
Ford C6TZ-4222-A Carrier Bearing Cup - $18.73
Ford F57Z-1S190-AA Front Axle Seal - $17.16
Motorcraft SY-75W140-QL 75W-140 Synthetic Gear Oil - $21.22




Did they by chance mention a power limit for those? Did they mention it's as strong as the stock diff, or more, less, or didn't say anything? I'm headed towards 500HP+ some day, and only if I could spin the front tires might I have a worry about that diff.

What is the ideal backlash for the front, .009-.012 like the back?

The front Dana-35 backlash range is .005-.008, the rear 8.8 is .007-.015
I talked with my friend and he said the backlash set was .006 and not .004;
when he took the picture the reading changed a few thousanths when he
let go of the assembly.

There are actually now four Torsen differentials that could potentially be used in
the Ford 31-tooth 8.8. The Ford pre-loaded Torsen T2 from the FX4-II Ranger,
Ford Racing M-4204-T31 T2 (2003-2004 Cobra), Ford Racing M-4204-T31H T2R
(used in the MUSTANG FR500S race car), and a new T2 that is used in the
new Mustang applications (like the 2012 Boss 302), which will be available as a
service part from Ford shortly. The 2012 Boss 302 service part is distinct from
the Ranger FX4-II service part in that it is not preloaded, has a higher TBR level,
and is about 30% stronger as well. The two parts that sold through Ford Racing
are the aftermarket T2 and T2R models.

I don't know about the capacity of the Dana-35 Torsen unit, but it certainly
looks much stronger than the stock Ford unit, and the T2R for the Ford 8.8 looks
incredibly beefy compared with the stock Ford Traction-Lok unit.

Rick Barnes at Torsen ( has been incredibly helpful and
can probably give you real world data on the strength of these units.

Pictures of the passengers-side leading shock lower and upper mounts shown;
it's right in the way of where the axle damper shock would go....


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Thanks, I probably spoke to him if he was there in 2003. I bought two for the 8.8's then, both from Reider Racing @ $450ish. I learned from both of them that the Torsen they had then wasn't the odd ball type like the Explorer, and Reider had supposedly modified one at some time before then.

I haven't had enough power to know if the early Torsen I have will be any worse than the later type. They have been adding preload and altering the built in torque bias over the years. So far I love how mine has been, but AWD keeps the back from being taxed. My 99 V6 with auto 4WD often spins the rear tire(traction lock), when the automatic feature doesn't function. The AWD is more dependable.

Bump, they should be close to producing the next run of the Torsen diffs, for the front of 95-01 Explorers. Time to contact them again.

"Torsen 975420-0207B Dana-35 T2"
"Rick Barnes at Torsen ("

Contacted JTEKT Torsen ...
ph 585-464-5000, ask for sales.


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