Fortin and Proformance front differentials. . .information. . .


Well-Known Member
Just saw the Geiser Brothers 4WD TT in the newest issue of DirtSports & Off-Road. . .saw they were using a Fortin front differential so I thought I would look it up. . .

. . .it's on the website, but there is absolutely no info other than the cost (which is $17,200. . .not a typo on my part). So obviously I'm not interested in buying one ($$$), but I would like to no a little about. . .especially what is so special about it that it cost $17,200!!!

I have seen the Proformance Ultra Narrow front differential before ($10,100 - $11,600 not including upgrades) and I get it that there is a LOT of engineering and machining in there, but as a Tool & Die Maker I know without a doubt those things could be made for WAY less (at least the Proformance ones since there are enough pictures to see what is involved in them) if you are just looking at material cost and machine time. . .is it reasonable to recoup R&D costs and that high of a rate?

Anyone have any info on this???



Well-Known Member
I can respond for Traction Products Inc.

We design and manufacture everything in house from the input to the outputs. We make the housings from billet. Not cost effective but flexible for the vehicle designer. We have several different front and rear differential arrangements. It would be great to reduce costs of manufacture by going to castings but it is difficult to have a fits all ends all design.

The latest Menzie Pro 4 has one version and the Armada Ultra 4 has two other versions. One has a 3 inch offset input. One has a 5 inch offset input. The last one has a 1/2 offset input. There are rh and Lh input ring and pinions. The final drive is drasticly different between the two trucks.

See the problem we have yet?

Our goal is production but the odds that the offroad racing market has to make us capable of reducing costs are slim. Last year the Unlimited 6100 class banned our rear diff before we could race one. So why should we invest in tooling?

We have tooling we have been looking at since the Micky Thompson offroad era, We dominated with Toyota all seven years. In the end the new series that came up after made our transmissions illegal to race. They still are. We did not sell enough transmissions to recoup costs of tooling.

Pat W
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Well-Known Member
I'm not sure you are going to get a "reason." Aside from Weismann doing some great things to package the input and output, their designs are very efficient....meaning more HP to the ground/wheel. They do not have hypoid gears, and some have said a hypoid diff is responsible for at least 9% of the hp loss at the wheel. Many 4WD racers are seeing 700 hp crank but only 4-500 hp wheel. Weismann is good at minimizing that with tons of F1 experience.

A more efficient differential(s) can gain you horsepower....At a cost (to a class) In the classes where rules are more open you are seeing more movement their way....

Early in the Sidewinder IFS/IRS Diff program, Pat was saying that there was slightly less then 200 hours in machine time (Including gears presumably.) Hopefully that has diminished some. But there is also the design time to produce an input in almost any location you may want and a CV location anywhere from back-to-back to the typical 9" diff flange to flange distance of 14".

The rare air players seem to be Forttin, Proformance, Tubeworks, Weismann, and not wanting to play...Holinger engineering. Plus some other rally shops. There are also quick change and billet 9" units in the $6-7k range for consideration.

Each have their benefits. Each have time lines that are not "off-the-shelf" and can affect a racer program choice.