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

[sand_in_my_mouth]

Hey there,

My son and I are working on project to be a DD + camping + light off-road rig (prelander, I guess). It's a 1996 F-150 with stock 302 and 4R70W (auto 2wd) transmission. We're converting the truck to 4x4 and have a year do it while he gets his license. It's a super cab short bed (so has the long drive shafts/carrier bearing).

To get started, we bought a non-running donor truck, which is a 1992 F-150 with 302 and M5OD manual trans and directly attached BW1356 manual t-case. The axles are factory 4.10s (Dana 44 TTB front with manual hubs and Ford 8.8 rear). The donor is a standard cab short bed, so a much shorted wheelbase than the DD we're converting.

We basically bought the donor truck for the axles, dash, door panels and a few other parts. Even though the factory 302 is a dog, I think that the 4.10 axle gearing will be fine for skinny 35s on 15" wheels (i.e. low rotational mass). We want to keep it stock width and mid travel for now, so I ordered some Desolate suspension parts. I'll probably add a lunchbox type locker to the rear.

I'm trying to get my head around the transmission + transfer case setup.

I'm probably wrong, but I ~think~ that these are the most obvious options:

• Factory style retrofit- Find/buy a 4R70W / AODE with 4wd tail/adapter. I'm not sure if this would bolt directly to the BW1356 and if the shaft output from my trans will work. It seems like I might need a new crossmember and possible an ECU from a 4wd '96 f-150. And maybe a new transmission wire harness? Any feedback on this option is appreciated.
• Divorced t-case- It ~seems like I could run a short shaft from 2wd 4R70W to some divorced t-case, like an NP205. This is my own made-up idea, so maybe I'm way off. I'd need to determine how best to shift the NP205 (or whatever divorced case would be strong, fit, work best, etc.). This seems like it might be the easiest and cheapest, but I'd need a t-case support/crossmember, and some custom driveshaft work. Seems like I could get good angles and have lots of strength. And it seems like I could forgo any electronic issues. But maybe I'm way off? Otherwise, I like this option because it keeps the trans in place and all work basically occurs behind it.
• Manual transmission swap- Obviously, I could try to swap the donor truck's M5OD and mated BW1356 into the supercab. I've read that I'd need a new ECU, new steering column (also from donor truck), and obviously the clutch/pedal/shift assembly, and perhaps this would be an electronics nightmare because of the pre-OBD2 to OBD2 issues. My son wouldn't mind a manual transmission, but this seems like the most work.
• Variant of manual trans swap- Same as above except find a ZF 5-speed manual to use instead of the M50D. This would be burly, but probably no easier (and more expensive).

Truck goals:

• Reliable- We want to get many years of use for around town, nearby camping trips, and moderate off-road capability, i.e. just for fun.
• Budget-friendly- I figure/hope that the 4wd swap will be $2k - $4k, not counting axle rebuild/refresh, suspension parts, etc.
• Homemade- I'm an average mechanic, but just bought a small welder and am not afraid of mistakes (I'm good at making them ;-) My son and I want to do as much of this project together as we can.

Thanks for reading this! Any transmission and t-case suggestions and insights are greatly appreciated.

PS- Here's the truck as it sits today with cast beams and 31s.

 

[85Yota]

I got that trans and manual shift 4x4 t-case from same year range F-150 for sale. In Lucerne Valler, CA good rebuilt trans ready to go. DM sent

 

[85Yota]

You can go divorced np205 t-case from a 70's and just mount that and do a short slip shaft to that and then new driveshafts. In Cali those t-case's are really hard to find because 05+ superduty axles are popular and this is solid setup to convert a truck/van/RV etc to 4x4 easily.

 

[sand_in_my_mouth]

@85Yota DM'd ya back. I'm too far away, unfortunately.

Any thoughts on 4R70W and mated t-case VS using my stock (2wd) 4R70W to divorced t-case?

Also, I've heard that since my '96 was (maybe???) the first year of OBD2, I want to avoid part swaps that require wiring mods as much as possible.

 

[sand_in_my_mouth]

Ah, thanks! That's exactly what I was thinking...divorced NP205...if I can actually find one.

 

[36Fan]

Just get a 4r70 for a 4x4 and use your same transfer case, no need for a 205. The computer will work as needed and no problems. If you have some fabrication abilities and want something better then I would do a 6r80 with the 1356 manual case and US Shift controller.

 

[sand_in_my_mouth]

Thanks @36Fan -- this is helpful! Sounds like swapping our 2wd 4r70 for a 4wd 4r70 is the easiest (and maybe the cheapest) move to complete the conversion. I didn't realize that the exist ECU would work, so that's cool.

Per your post, I'm looking at https://www.usshift.com/6r80.shtml and reading 6r80 specs. Six-speed and a 4.17 first gear would be a really nice upgrade. I wasn't aware of this option. I'll call US Shift tomorrow to get a better handle on that option too.

 

[36Fan]

The 6r80 drives night and day difference than the 4r70 or even the E4od. No idea what you mechanical abilities are so I can say its difficult or easy, but to me it was an easy process and I've done it with a kit and also machined my own bell housing bolt pattern etc.

Easy and fastest way, find a stock 4r70 trans and be done. You have a 96 which is OBD2 so thats a plus.

 

[sand_in_my_mouth]

I can imagine that the 6r80 would make it drive/shift like a much more modern truck. I bet that there are more of them in the u-pull lots too (as compared to the one or two years when they made the *special* 4r70).

 

[36Fan]

Yes, there are plenty but its a job and pricey compared to the 4r70. I dont feel the 4r70 is anything special, you should be fine. I have a 4r70w in my 67 Bronco behind a 347" SBF and a Dana 20 transfer case and Advanced Adapters, easy to do.

 

[85Yota]

You're over complicating an older truck. Get a 4r70w and tcase that's behind it and go. It's a 5.0 f150 not a modern truck and it never will be. Spending the extra money on getting the 6 speed working youd be better off selling the 2wd truck and buying a 4x4 and building that.

 

[kcb]

You will thank yourself by keeping it simple and using a factory configuration for that vehicle as suggested above (based on the scope of the project you describe). Anything outside of that will be exponentially more work.

I have 1991 Reg Cab that had 300-straight 6, M5OD, 2WD from the factory. Found a 4WD M5OD and t-case (opted for a Bronco T-Case to eliminate the slip yoke). Everything bolted in and all the small tedious parts are available from the junkyard, ebay or donor vehicles. The hole in the floor for the t-case shifter is already there. It did require a custom driveshaft in my case.

I eventually put a 5.8/351W in front of the M5OD and beat on this thing in the dunes and everywhere else and the trans hasn't complained a bit. I have a ZF sitting in the corner as a backup, but it hasn't been needed and I honestly think the wider gear ratio spread would a pain off-road.

 

[85Yota]

The newer transmission is nicer but putting it behind an old 5.0 you'll never get to feel the added benefits. If you want modern engine transmission do a 7.3 godzilla swap into it.

 

[sand_in_my_mouth]

Good morning, guys. Thanks for the additional feedback. This is useful and exactly what I'd hoped for--some good insights on what will work best for this project. I realize that it's a really simply build by BL/GT standards, so I appreciate you all taking the time to respond.

@kcb I think you nailed it. I'm wanting reliability, which is probably closely related to serviceability, so ease of access to parts that succumb to normal wear and tear is important here. Having a truck that's close to stock is probably best for a teenager's daily driver. He can also go nuts and back-half it, swap engines, buy an Atlas...later, if that's what he wants someday.

It's interesting what you're saying about the M5OD, because that's what's in the donor truck. I've heard mixed things about that trans (someone described it to me as a grenade), but then I've heard from actual owners like you who beat on it and really like it). I'd love to swap that trans into the super cab, but if I'm understanding it properly, it's way more work than I want to bite off. Am I correct that I'd need to:

• Find an OBD2 (1996) ECU for a manual trans f150 and install?
• Replace or rebuild the steering column (or is it as simple as removing the column shifter and bypassing the neutral safety switch)?
• Splice in the proper transmission harness or similar?

The easier part of a manual swap, to me, seems to be actually moving over the trans and attached t-case, and swapping in the clutch and pedal assembly, shifter, etc. I have 100% of those parts hard from the donor vehicle. I feel like I could get the M5OD and BW1356 rebuilt locally without much risk or expense, so fully refreshed parts going it. I should add that I found an incomplete thread or two online about this swap, but they weren't detailed enough so as to be clear to me. However, maybe if there's no ECU replacement and little wiring (i.e. just neutral safety and reverse lights...simple stuff), then I'd be leaning toward manual shifts! That's always fun.

Does anyone have experience with this swap, particularly if it's from a pre-OBD2 into an OBD2 truck?

 

[85Yota]

I have no experience in swapping them in. BUT i do know the M5OD trans isn't that strong, some have luck with it when driving it mild but if you really beat on them they don't last too long. I would highly suggest you find a 4r70W and swap that in. The only difference I know of between the years is I believe the plug on trans changed but I believe it's a simple part to drop pan and swap from your's into the 4x4 one.

 

[bullnerd]

Sounds like you want to be working on the donor truck?

 

[kcb]

As a huge fan of modern autos... the manual transmission is nice on these old trucks for simplicity and making use of the little horsepower, so the swap may be worth it. When I say beat on the M5OD, I do mean power-shifting in 4WD with 35's while climbing dunes. If you have less luck down the road, the ZF looks to be a plug and play swap from the M5OD.

From the top of my head:
Flywheel - donor truck
Clutch - recommend new
Slave cylinder - recommend new
Crossmember? - donor truck? no idea how the 4R70W compares to the M5OD
T-Case - be aware of the speedo output compatibility (mechanical/electronic). Also if you can find a bronco one for cheap, they have a bolt on flange instead of the slip yoke
Driveshaft - A lot of variables here...

As far as the electronics, I would source an ECU first and get a wiring diagram. A manual transmission ECU might not care about any of the transmission inputs. The reverse light switch is the only wiring that really matters on the trans I believe. Transfer case High/Low position no longer matters for shift strategy or anything. ECU pretty much just needs to run the engine and then use your own brain to operate and monitor the levers.

 

[sand_in_my_mouth]

@85Yota definitely point taken about keeping it simple. I'm just trying to understand how much less simple it would be to use the parts that I have. (That, and I grew up with manual transmissions in trucks and tractors, so I have a soft spot for them.)

@bullnerd it's funny you said that, because I am actually eager to work on the donor truck! That project is at least a year out (need to finish my son's truck first). Right now, I'm trying to remove the entire donor truck drivetrain (either for reuse in the super cab or for giving away what we can). That '92 is a flareside in full redneck majesty. See pic below. The wheelbase is 117.5". My tentative plan is LS + GM trans swap, link the rear, and 4" over beams up front under a one-piece fiberglass front end. I need it stripped down to nothing, because most of the floorboards need to be replaced and the frame needs to be blasted/sealed. And, truly, the previous owned hacked up every component that's not bolted shut. I had considered rebuilding it as-is, keeping the Ford drivetrain, but it's too far gone for the toy that I want to end up with in ~3 - 5 years. So, it ends up that the donor truck is actually my future get-stupid rig (definitely not a DD ). I don't have the skills to build it yet by myself, so I'll need to learn a lot and lean on smart folks here, in the local shops, etc.

@kcb "...manual transmission is nice on these old trucks for simplicity and making use of the little horsepower, so the swap may be worth it. When I say beat on the M5OD, I do mean power-shifting in 4WD with 35's while climbing dunes."

That totally resonates with me!

And it lets us get more use out of the parts coming out of the donor truck too. Good points above too: I'd def get a new heavy-duty clutch, slave cylinder, probably new manual starter, and might end up needing the driveshaft customized. Over lunch, I did find another forum where the user claims to have done this exact swap without replacing his ECU. Idk if it's cool to link to that other forum, so I'll just paste his quote:

---

i have to disagree about swapping the ecu. i swapped out the auto in my 96 f150 with a 5.0. installed a m5od and kept the ecu for an auto and been running with it for 2 years with no problems. the only codes that show up when scanned are for the tranny sensors.

---

I did see that a new ECU would be required for cruise control, but we already disabled cruise when we ditched the airbag and installed the new steering wheel (didn't trust that '96 airbag, especially off-road). So, my takeaway is that the ECU might or might not be required to run, but the engine would probably prefer to know that the trans is manual--maybe better mileage, performance, etc. with a proper ECU. Just a guess.

Here's the future project looking sad and so tired right now. That's what $600 gets you around here. If anyone is partial to these factory chrome wheels, just take a trip to Florida and you can have them.

 

[85Yota]

I sold all the stuff to convert a 2wd to 4x4 and manual trans. m5od trans vw1356 t-case driveshafts and trans crossmember although i think they're the same. he ran auto ecu and didn't care about CEL or Cruise control he said. It was a 94 truck so OBD1 and no MAF. Speedo is ran off rear axle VSS

 

[sand_in_my_mouth]

Thx, I was thinking that the speedo ran off of the VSS on the 8.8, but wasn't sure if there's more to it.

I have the entire assembly from pedals to t-case for the M5OD-R2 + BW1356 swap (plus the D44, front driveshaft, and 8.8 that I was moving over anyway). And it makes me think that a factory driveshaft configuration is out there, because surely Ford made a super cab short bed manual 4wd, right? So, I need to find that truck--probably any OBS with that config--and pull the rear driveshaft.

I just crawled around under the two trucks for half an hour. I might have to remove the steering cols to get it all swapped, but I have to replace the entire dash in the super cab anyway, so I'll have it opened up sometime soon. I just priced flywheel, clutch, master/slave, and related parts, along with various bearings. It all seems reasonable.

Big thanks to everyone who chimed in! I'll post a new thread when I get it going.