Fortin UTV drive shaft sprag

JerryB

Well-Known Member
Fortin is making a sprag gear for the drive shaft on an X3, which allows the front wheels to coast under off throttle moments. I can see it assisting with brake bias like they claim on their website, and would presume it would take some of the wear and tear off the front diff under braking as the rear end isn't trying to force the wheels to rotate. Anyone have any experience with using one? Has it increased front diff life? It's pricey, would have to significantly increase diff life for me to drop the money.

1589252321408.png
 

JerryB

Well-Known Member
Yes, but many run some version of a locker. Problem with UTV is under braking/off throttle the rear end is constantly trying to continue driving the front wheels, resulting in diff wear and driveshaft damage. I have seen a few instances of actual drive shaft rotational twisting of the tube till it shears.
 

jon coleman

Well-Known Member
heck, wouldn't a selonoide operated coupler work?, so when you hit brakes hard enough, driveshaft de- couples, , then, when you touch gas pedal, it locks back up, i got a much cheaper solution in my brain than a sprag
 

isdtbower

Well-Known Member
I think the sprag is there to allow the front wheels to coast out on a front wheel landing... Instead of shocking the whole drive line system... Which may be "going slower" than the landing speed.

"I think" the sprag only engages the front when the transmission/xfer is pushing the front diff. So I doubt it would disengage the front if the rear is still driving the front during braking??

Apparently popular in Pro4 and in some Weismann front and possibly rear differentials in Ultra4. (Are thy still called a differential) Also Indy and F1. Some have considered them but didn't want to chance not having a locked front in 4x4 in reverse...and $$ . Birdies say that they can be in Xfer cases also. Need an expert.

(And the rear brakes should help the front brakes stop thru a normal mechanical driveline.... ) Our "group" has always thought that brakes cause more maintenance damage than accel stress.
 

jon coleman

Well-Known Member
also, dont have touchy brakes off road, you want to have to Really stomp on the pedal to lock up wheels, worst thing for an off road car is locked up wheels, all the weight on the front, slamming into big holes, better to just let car banzai over those Big maneater holes with wheels rolling!also noted most important point^, $$$$$!
 

JerryB

Well-Known Member
Agreed on the damage caused under braking loads. First thing I learned about driving one of these is to let the car "roll" into the rough sections (ones you need to slow for, such as coming into a whooped out corner). Stomping on the brakes really loads the diff, drive line, ball joints, etc. and you'll end up breaking something. Was just hoping I could find someone who's actually used one to get their thoughts on whether or not worth the $$$
 

jon coleman

Well-Known Member
better yet i figured out solution, fluid coupler, fill the turbine style ' converter' coupler with magnetically/ electrically controlled viscosity oil , coupler is open off the gas& on the brakes, full throttle the converter oil goes full thick, and locks up coupler to the level that driver is happy with ,when off the throttle, electricity controls amount of front ' bite', & its adjustable on the fly w a reostat knob, all it takes is some of Mercedes Benz f 1 r& d cash to figure it out
 
Last edited:

isdtbower

Well-Known Member
Best, is to talk to Doug Fortin. You have the right questions. Because of "Magic" a Weismann "unlocker" can work in reverse if wanted. Not sure of others.
 
Top