So I bought an Mfactory pro 4.0 final drive did my install break-in proc. And all that good stuff, went to the track did some traction,60ft,and top end test passes then wne to go do an all out pass launched @6800rpm and 4lbs boost car hooked a 1.40 60ft and had a decent run car did 9.0@158 did some tune adjustments dropped some tire pressure and went for another pass, left the hole nice hit 2nd and wiped the teeth off the countershaft a total of 4 passes only 2 that actually had some power launching. My stock LS final drive had over 40 dyno pulls and 12 passes with 3rd gear burnouts 1.40 -1.48 60ft times 9.7-9.2 passes 146-152mphs. considering the car only makes 775hp&508ft. lbs i dont think these should have broken seeing as they are rated for 1000hp

 

have you contacted MFactory? Everyone i know says they have top not service. did you install the FD or did they install it. If i were you i would contact them first. they are one of the few that actually support the sport. No need to come out and bash there products.

 

its the Canadian way, dont ya know?

 

I used the street version for 2-3 years with no problems.
Are you using a stock bellhousing? If so, I don't think it is fair to blame the final drive with the times you are running. For a car that is hooking that hard, you need a bell housing that will keep the final drive from trying to seperate and flexing the bellhousing. Right now, the only real option is a billet housing or a properly braced housing.

 

I had it installed here. I have already contacted them and he simply said we do not warranty our product. Although the person who I spoke to on the phone when I was ordering said as long as it was installed properly he would stand behind it.

 

also we have had problem with the housings but never the gears or fd! check all of your shims and back lash. we have well over 50 launches on our no problems!

 

My housing is braced properly all the shims and backlash were checked at time of install, all was well. This was not an installation error or housing failure. I purchased 2, both 4.0 pro's I had over 50 passes on our other one with no problems at all in our street class car , then I installed it back in Same housing as it was deemed reuseable and put it back to the test in the H/R car I have already had more than 15 passes cutting 1.4 60fts, 8.8-9.0 160+mph passes will not 1 issue

 

How do you set backlash on a b series ring and pinion?

 

setting backlash on a b series trans is just impossible but it was still checked upon installation to determine wear on the bell housing. and to set the record straight i am not here to bash on Mfactory's product like i stated i purchased 2 and have well over 60 passes on the second one without problems same case, same gearset, all the same variables.

 

You said the housing was deemed reusable, was it cracked previously or by reusable did you mean you inspected it and found no signs of cracks or warping?

There is no shim adjustment for the CS as it doesn't use one. Only the diff and mainshaft use a shim.

MFactory's warranty provides that the product is in working condition upon arrival, but is only covered once installed if MFactory or their Official Installer (myself for North America) install the part.