Hi, I just bought a 1985 f150 with an inline 6 and a four speed manual transmission in it. I'm looking to convert it to a 5 speed manual tranny and was looking for some suggestions on what transmission to get and such. (I'm poor so the more cost effective the better haha)

Thanks,

Tim

 

Good friggen luck finding a zf5 smallblock !
If the motors stock or close to stock, get a Mazda unless your gonna haul with it.

Look at my official build thread and in the next week or so I'll be wrapping it all up.

 

Haha fair enough! yeah I was kinda wondering if those were pretty rare..

Thanks man and will do!

 

Yeah I've spent some time trying to find a used one.
Car-part.com has plenty listed. Rebuilt go about a grand.

So far I'm just getting to the tricky stuff.

There's a good thread on one of the m5od swaps that is all about measurements and such that helped me a lot.

I'll look for it and let Ya know!

 

Okay cool.
I'll have to check out that thread for myself here pretty soon. Thanks for the help and good luck finishing the job man!

 

Yes, the ZF5 is a stouter trans, but harder to find and rather pricey.
The M5OD from an F150/Bronco would be cheaper and easier to find, but they aren't as durable when the truck is used for hard work. These also have one area where they like to leak, the shift rail plugs. They are rubber and tend to leak. If they are still in decent shape, you can pull them out and seal them with silicone, or replace with steel "freeze" plugs. The latter is much harder to get back out, should the trans ever need to come apart......

Neither trans is a direct swap. The trans crossmember has to be moved back, and the driveshaft needs shortened (2wd/4wd, the front on a 4wd needs to be lengthened), as they are a bit longer than the C6 and manual trans that were used in these older trucks. If pulling one yourself at a salvage, grab the upper crossmember braces along with the crossmember, it makes it easier. You will likely need the floor cover plate too. The ZF is a lot taller, and this piece is needed. Not sure on the M5OD.

Aside from strength, the biggest difference between the 2 is the gearing. ZF5 has a deeper 1st, with slightly wider ratio splits, but they end up with the same 4th (direct) and 5th (OD) is very close, if not the same.

The M5OD can handle towing, within reason, so long as it's not abused. I know a couple people that have had trucks with this trans for many years, and not had any issues. Both have gone well beyond 200K without issue. Another guy I know, lost the M5OD in his truck just a few weeks after he bought it, due to the leaking shift rail plugs, and failing to insure the trans was filled with oil. That kinda killed the mood on his honeymoon.........
I had one myself, and used it for moderate towing. Sadly, the truck got totaled by my former wife at 55K miles, but I never had any issues with the truck prior to that.

 

Hey thanks a lot! Thats super helpful information. The more I look at it the more it seems that I really won't need the zf for it is going to be a daily driver and a weekend work truck for the most part so thats good for both finding a tranny and my wallet. I really appreciate the info!

 

I have the M5OD in mine, it is original and closing in on 300k. I've abused it since I bought the truck last May, and put about 15k on it myself, and have no ill-effects. Does that mean I'd pull 10k with it? No, but they are reasonably stout themselves. The only issues I know of are the shifter bushings wearing away and causing a ton of slop, which is repaired cheap and very easily, the shift rail plugs, and the 3-4 synchros tend to be problematic sometimes. Gearing is closer than the ZF, which I like in a DD. ZF 5th gear is .76:1, the M5 is .8:1, so not enough difference to really worry about. In my case, driving at 60mph, I'd only drop RPM down by 80 with the ZF.

 

So basically what your saying is that as long as I don't plan on towing a lot, the m5od is the better choice, especially because its easier highway driving? It will be a daily driver for me once I get the new tranny put in and some engine tuning.

 

Yes sir. I'll be putting around 350+ ftlbs through my 300 so I'm not gonna risk it, plus there's a zf in my psd that has 300+k on it with no slop or issues.

 

Sure, that makes sense

 

That and a sas is in the process also.

 

Sure, I gotcha

 

For light duty use in a DD, the M5 would be perfect for you.

 

Sounds like i'm getting the mazda then!