250 Six cyl with M5OD

[Braddw25]

Hi everybody,

I have decided on one possible upgrade path for my '71 bronco with a 170 I6. I have decided that I am going to stick with an I6 in this bronco due to the fact that I have fallen in love with the little six since I've owned it. The only drawbacks to the 170 would be that it is a little lacking in top end power. FOr this reason, I have decided to swap in a 250 that I took out of a Maverick years ago. This will also enable me to use a wider variety of Tranny's due to the 250 having the same bellhousing and clutch as a Small Block. I am not planning on doing anything radical to the 250, so I was wondering if the M5OD Mazda tranny would be a good option. I am pretty sure that this tranny will bolt to anything that a ZF will bolt to, so I should be able to use any ZF adaptors to bolt in to my D20, and as mentioned before the tranny should bolt right up to the 250. I know the M5OD is not as strong as a ZF, but I'm not going to be pushing huge power numbers with the 250. Also, I understand that the shifter on the M5OD is mounted pretty far forward and causes some problems when installed in a V8 powered EB. I was thinking that since my 6 cyl will sit further back than a V8, that this tranny might be a really good fit due to the shifter being placed more forward. Does anyone else think that this sounds like a pretty good idea? Any thoughs or recommmendations would be greatly appreciated. I was planning on using the NV3550, but the M5OD seems to be just as good but would be more cost effective. Thanks for any additional info you could provide.

 

[Broncobowsher]

Sounds like a nice plan.
The M5OD was used behind the 300 for a few years, so a smaller 250 should be more then safe. You do know to replace the rubber plugs with brass freeze plugs.

 

[bfoldy]

Sounds like you've thought it through fairly well already.

I don't know if there will be a lot of folks familiar enough with this type of swap to give you a slew of input, but I'm sure there's a couple of guys on here with enough cross-brand experience to point you in the right direction.

I guess if it were me, I'd compare the bolt patterns between the Mazda tranny and the ZF. Then I'd figure the dimensions of the Mazda tranny to see what possible driveline and crossmember modifications will be needed to make it fit.

 

[bmbm]

250 with M50D

Hope you keep us posted on this. I had no idea this trans was used with the 300. I recently put a 250 and NV3550 in my 66 and the combination is great. At least for my driving this trans is perfect, easy shifting, good ratios and quiet. I am trying to get a friend of mine to sell me his practically rust free and straight 71. It has a tired 302 I think and a column shift. Want to dump the three speed and do the five speed and NV3550s seem to be getting harder to find. If you haven't been there yet go to fordsix.com.
Good luck with your project.

 

[73azbronco]

I think a 170 block is the same as the 250. The 240 block is the same as a 300.

 

[Braddw25]

Sounds like a nice plan.
The M5OD was used behind the 300 for a few years, so a smaller 250 should be more then safe. You do know to replace the rubber plugs with brass freeze plugs.

Yes I sure do. I actually had the unfortunate experience of having those stupid plugs leak and and destroy an M5OD in an F-150 a few years ago. Besides that problem, I really liked that Tranny behind the 300. Thanks for the input!

 

[Braddw25]

Sounds like you've thought it through fairly well already.

I don't know if there will be a lot of folks familiar enough with this type of swap to give you a slew of input, but I'm sure there's a couple of guys on here with enough cross-brand experience to point you in the right direction.

I guess if it were me, I'd compare the bolt patterns between the Mazda tranny and the ZF. Then I'd figure the dimensions of the Mazda tranny to see what possible driveline and crossmember modifications will be needed to make it fit.

All good points, and that is the part I am not completely sure of. From what I have read, as far as adapting goes, an M5OD is identical to a ZF. So adapting it to my D20 should not be a problem. As far as the lenght of the M5OD goes, I'm not sure. I was planning on having to replace and relocate the t-case cross member anyway, so I don't think that will be a big problem.

 

[Braddw25]

I think a 170 block is the same as the 250. The 240 block is the same as a 300.

You are right about the 240 and 300 as far as I know they are identical. The 170 and 250 are very similar. The 250 is about an inch and a half taller and has a different bellhousing bolt pattern. Other than that the are the same.

 

[Oldkool77]

I look forward to seeing more on this swap. Keep us posted.