frank5079

I'm going to swap my old tired 300 six in my '94 F150 with a 351 from a '95 F250; months before my truck's engine died, I had changed the fluid in the Mazda gearbox and it wasn't discolored nor did I find anything metallic in the old fluid. I even added a quart of Lucas automatic transmission additive which made shifting gears even smoother.

So here's my question...I just want to get my truck running again and I've heard horror stories of how the Mazda gearbox will grenade behind the 351 because of the huge torque difference and that I'd be better off finding a ZF 5 speed. Now I'm a very conservative driver and I don't plan on doing any hard launches from a dead stop or even pull a fifth wheel trailer. If I do pull anything, it might be my little 4x6 trailer with my 2000 Vmax. So what do you guys think?

88xlt

Personally, I would just run the Mazda transmission for now. I pulled about a 14,000 lb. loaded fertilizer spreader with my '88 F-150 about 15 miles once or twice a year for several years with no problems. It has the Mazda 5 speed transmission. Then one day I was just cruising down the highway empty and the transmission failed with about 220K miles on it.

You will have enough little mods to do just switching engines. You can always switch transmissions if or when the Mazda transmission fails. Just my opinion.

frank5079

Yup, I can see that but like I said earlier, I don't plan on hauling anything major in the bed or pulling anything bigger than my little 4x6 trailer with either my Vmax or lawn mower....thanks!! plus I was also under the impression that the ZF gearbox was more of a 4 speed with a granny first gear....

BLDTruth

Normally I would say ditch the M5OD but since you are not planning on building up the 351 then it should really be fine, and it will prevent a lot of headaches. It can handle 300/300 hp/ft-lbs

If you have the small block Zf5 and crossmember sitting in your garage and just waiting for the right opportunity to do it, then ok I won't argue. You will need to lengthen your rear driveshaft a little bit too.

And yes, the first gear on a gasser ZF5 is pretty much useless unless you are towing. It has a 5.72:1 gear ratio or something ridiculous like that. You will be starting in second gear for the majority of your launches.

frank5079

I feel much better about the M5OD gearbox after reading this....

http://www.fullsizebronco.com/forum/...ld-handle.html

Chris_1

iTrader: (1)

The M5OD is a really good transmission for what you want it for.
It's name doesn't sound as cool as a ZF but it's a way better transmission for driving around.