OBS F150 2wd to 4wd conversion: Any transmission/t-case advice?

[sand_in_my_mouth]

Btw @kcb are you saying that this is the less desirable t-case output pictured below?

Also if you can find a bronco one for cheap, they have a bolt on flange instead of the slip yoke

 

[85Yota]

I used bronco t-case on my f150 but I did a 9in and the solo vss relocation kit which needed the bronco t-case fixed flange rear output

 

[bullnerd]

Why is the 4r70 a better trans than the E4od?

 

[85Yota]

It's not but it's what the 5.0 came with the e4od is stronger from what i've read and what 5.8 trucks and f250s use. 4r70 is basically a new aod-e so overdrive c4 strength with some better internal parts than the aod-e but far from bulletproof.

I'm a chevy guy so it's like a th350 which is car/light duty truck tans and a 700r4 which is same thing but overdrive. I believe that's what ford did with the aod to get overdrive in the late 80's

 

[SEf150]

So, I recently did a scsb 2wd to 4wd, and have a m50d, as best as I could find no one makes a factory replacement driveshaft.
I ended up buying an auto trans driveshaft and cut a few inches off to make it fit.

Where in Fl are yall at?

 

[sand_in_my_mouth]

Thanks for the heads-up @SEf150. Maybe there was never an scsb manual 4wd from the factory? Idk.

Jupiter for the last decade, but I'm looking west pretty hard. Where are ya in MS? Like it?

 

[SEf150]

I'm in Lucedale, on the MS/AL line. I like MS, much better than south Alabama.

 

[kcb]

Btw @kcb are you saying that this is the less desirable t-case output pictured below?


View attachment 35040

Yes, the Bronco tailhousing is shorter and has a flange to bolt the driveshaft to. I had a custom driveshaft with a slip-joint made by Tom Woods. The slip joint on the t-case is a weak link and if I ever damage the driveshaft I can un-bolt and get home in FWD while all the fluid stays in the t-case.

Oddly enough, I found a front driveshaft off some other OBS Ford that can bolt in as a backup to get home, but that's just pure luck for my application.

 

[sand_in_my_mouth]

That's cool. Got any pics or a build thread of your truck? Was the M5OD already in your scsb and you added t-case + front axle? Or was it auto and converted it all?

 

[kcb]

 

[sand_in_my_mouth]

@kcb makes sense. I can see how this (my) t-case slip joint could put a lot of leverage on the rear of the case.

Our super cab has a carrier bearing mounted to a crossmember, while the donor truck doesn't. I am wondering if I can use a custom short shaft to span from the t-case rear output/u-joint, through that carrier bearing, and then to another u-joint that attaches to my current factory driveshaft.

In other words, I'd use the factory read driveshaft, but I'd use a stubby shaft to connect it to the t-case. That stubby shaft would run through the carrier to keep it all still and prevent a load from being exerted on the back of the case. Idk if carrier bearings should have u-joints on each side of them...probably not.

If anyone has solved this problem and has pics, feel free to post them ;-)

 

[kcb]

That's cool. Got any pics or a build thread of your truck? Was the M5OD already in your scsb and you added t-case + front axle? Or was it auto and converted it all?

It's the avatar pic. '91 reg cab shortbed. Had a straight 6 and M5OD, 2WD from the factory.

First I converted to 4WD with the TTB setup and coilovers, junkyard M5OD 4WD version, and found a manual shift bronco t-case. Custom driveshaft with 1350 u-joints, flange on both ends and a slip joint.

Once the straight 6 cracked the head, I found a '95 351W from another F-150 and swapped it in.

Keeping everything factory based made life pretty easy, especially for all the little stuff you can just grab in the junkyard versus killing your momentum.


I forgot you had a 2-piece driveshaft, so the slip is currently in the rear part of the shaft, but I guess that will change with the conversion. I think a bronco t-case with custom 1-piece shaft would be the ticket

 

[sand_in_my_mouth]

Yeah, that makes sense--I'll try to find a bronco t-case. I like the factory style. That's my preference too--keep it easy to maintain, because it'll probably need frequent work.

 

[SEf150]

Mine was originally a 4.9/m5od truck, I found a guy parting a 91 f150 and bought the front end, trans/tcase and x member. Everything bolted in drivetrain wise, I sourced a automatic trans rear drive shaft and trimmed a couple inches off to make it work.

 

[sand_in_my_mouth]

@SEf150 that's badass! Pretty much exactly what we're going for: bed rack/tent, 35s and lowish center of gravity.