I have the six speed Zf6 tranny in my 05 F-250 and i have heard a few different numbers about what the tranny can take clutch aside. What numbers can the internals take before they give? also i was told there are no build kits for these trannys. no built gears or forged anything. any help would be great thanks!...also........ I was hoping someone has gone over 500 with their ZF6. My goal is 500 hp. My buddy with a 04 1/2 dirty with a zf6 has a PPE and a fass with a south bend dual disk and his is all messed up....we think its the fly wheel or somthin. its a beach and a half to get into gear. he heard from someone that the ZF6 can only hold up to 500 and his truck is roughly at 445 were guessing with his mods going by other ppl's dyno runs with the same set up. anyone else have any say on the subject? Thanks!
Reply With Quote...i had both these postes in the 6.0 aftermarket section but i didnt get a whole lot of help.
Mine has about 508-542 hp running through it, depending on the dyno. I've put 38k through it with that and it already had 110k on it from before. Some of the dmax guys have quite abit of hp going through theirs, and they are still alive.
My brother has a 99 with a zf6/cummins. He runs about 450 hp. He swapped the powerstroke out at 190k. Now he has 300k and the tranny is still great. He also tows alot and he has a single disk sb ofe.
Mine- 1995 Ford F-350 XLT CC 2wd DRW LB, ZF-6sp, '96 215 hp Cummins, SBDD, #10, SDX 5x14s, HE351cw/S475/1.10 twins, and other good stuff
My Newest-1995 Ford F-350 XLT CC 4x4 SRW LB, 460 gas, auto, Soon to be 12v Cummins, 4r100 and 700hp+
Wife- 2008 Ford F-350 Lariat CC SB 4x4 SRW, 20" factory wheels, navigation, sirius, all stock for now
The ZF6 is actually a pretty tough tranny. They have been known to hold pretty well in the pulling side of things with just a few exceptions once you really start putting the power to them. They don't like to shift fast and if you add in a dual disk clutch it takes longer to allow the synchros to mesh. If you just jam it into gear you trash the synchros and it makes it harder to shift. Some of the input shafts have been known to wear on the splines over time with some of the aftermarket clutches depending on what clutch disks are being used in the clutch. The first thing that actually breaks is the output shaft if you've got the power to do it. Usually this happens in sled pulling when we have the power to go to 4 high and can grip the track well. I've broken some, Bean has broken some, Jon Jon (a dmax in Indiana) has broken some, and Evan Davis ( a dmax here in Ohio) has broken some. There are likely others, but these are the ones I know about off the top of my head.
These trannys can take a whole lot more than 500Hp and be just fine.
At what point (hp) do you think they start breaking.
Bean was probably north of 750 when he started having trouble with his (maybe Ryan can confirm that since that is a WAG on my part). Jon Jon didn't start having trouble till he was north of that figure. Evan's truck is a NASTY 2.6 truck that I can honestly say is every bit of that figure. I can't say that mine was that powerful, because I also had a bounce at the same time, any figure I could throw out on my truck I can't back up so I'm not going to, but it was north of 500 HP for sure.
The synchros being shot have nothing to do with HP levels - that is a function of the driver and clutch setup.