I'm in the planning stages of making my truck four wheel drive, and I have a few questions. I've searched the forum and didn't quite find the answers. And don't tell me to buy a 4x4 truck. Now that that's out of the way...

The truck I have is a '91 F-150, 302, M5OD 2wd. The truck I'm looking at for a donor is a '90 F-150, 351, Auto (E4OD?) 4wd.

1. If I have read correctly so far, all 1/2 ton frames are the same, making major components strictly bolt-on. Is that right? What about transmission crossmembers? IFS members bolt directly on? Steering box is the same? Spring mounts are the same?

2. What am I getting into with transmission tailshafts? Can I change only the tailshaft in my M5OD, or will I need a different casting too? Any chance I can swap tailshafts between the E4OD and M5OD? I also intend to put my 2wd parts back on the '90 and resell it.

I'm sure I'll think of more but let's start with that. Thanks for your help.

Daniel

 

You should just buy a 4x4.......

Seriously, your transmissions aren't gonna interchange at all, you should at least look for a donor with the same trans.

 

Well, I'll throw another option at you. Looks like you've got an ex-cab longbed? That should give you plenty of wheelbase to run a divorced xfer case setup if you wanted. Get a divorced NP205 & build a xmember to mount it. You'd need a short driveshaft to run from your 2wd M5OD to the input on the 205. This basically keeps your tranny as is. If going through the pains of doing a 4x4 swap I'd just do a SAS up front. 76-79 F-150 or 78/79 Bronco will have the high pinion, disc brake D-44 front that will mount right in with relative ease & have the same bolt pattern as your current wheels.

So, long story short: SAS up front, divorced xfercase, some driveline work and you're a 4x4.

 

Yes, you can just bolt the front-end complete from the 4x4 onto your 4x2 frame. The 4x4 frame is boxed on the ends just behind the bumper, that is the only difference. You will not need to change out the rear-end at all, assuming it's the same gear as the donor. Just use blocks to jack it up to the desired height.

There is not anything you can use from the E4OD on the M5OD. You will need to find a 4x4 M5OD or a ZF5. You can use the existing trans mount from your 4x2 truck.

I converted my F150 to 4x4 so I have done this already. I went a little further, tho. It was originally 300 Six, E4OD, and 4x2. It is now 460, ZF5, and 4x4.

 

Or, you can keep your same trans, swap the 2wd output shaft for a 4x4 output shaft, get a M5OD extension housing, then just bolt the TTB front end and transfercase to your existing trans.

 

That's exactly what I was thinking. With 108k miles, I'm not going to find a better transmission. This extension housing you mentioned: is that a bolt on to the existing transmission or is it actually a different transmission casting?

 

You gotta tear down the trans completely to get the output shaft out.

 

No, It should bolt onto your trans. It replaces your tailshaft for the 2wd, and the transfercase bolts to it. So it goes trans, ext housing, transfer case.

Yep, I'm talking complete tear down.

 

uhmm am i the only one noticing that he hasn't said anything about rear end gears and how 4x4's normally are geared different then 2x4's? might want to look into swapping out the rear end too.. and as for putting your 2wd back to the 4x4 truck.. none of that is going to fit well either.. i believe the two trannys are different sizes completely.. so the driveshaft from yours wouldn't fit on the back of the auto to the front of the rear end.. the smartest thing and most cost efficient thing you could do is what you asked us not to tell you.. altho if you really want to keep your truck, why not buy this one as the doner truck and just make it your 4x4 rig and keep the 2x4 truck as your driving truck? that way you are suffering the bad gas mileage that 4x4's bring.. that is what i would do at least

 

All I'm saying is it can be done. Mine was 2wd. I thought it was stupid to but another 4x4 truck, do all the work I already did to mine, (paint, engine, trans, ect) then just to rip out the front axle and put a solid axle in. (Yes, I wanted to solid axle).

So I got a 79 axle, BW-1356 transfer case, AOD extension housing, and AOD 4x4 output shaft. Tore down my AOD and replaced the output shaft, and I got 4x4.

Check out www.wittrans.com they sell trans parts cheap. Get my extension housing for $30, and output shaft for $50, seal kit for $20.

 

People who would suggest, and there always seems to be someone, that you should just sell your truck and buy a 4x4 do not have a clue about the attachment we get to a particular truck. Plus, as these trucks are pretty old, it's hard to get a replacement that will match what you already have, especially if you already have an investment in other mods as SCR points out. Converting your existing truck is the only way to fly, IMO, and you will enjoy your truck even more knowing you made it more uniquely "yours".

My conversion was super-cheap, I traded some work for the front-end and I got the xfer case with linkage for $100. I spent another $100 on having the rear driveshaft made up and that was it. All the other misc. parts like blocks for the rear-end I already had laying around.

 

YOUR truck is familiar territory and you get to know YOUR truck.Buying someone elses truck opens up a can of worms and involves a whole new learning curve.Takes me a lot of thought and pondering to let go of one of my vehicles.Sounds silly when I admit it though.

 

The donor truck I was looking at had the same gears, 3.55. I'm aware of that issue.

As for buying another truck, uh-uh. Dad (Mark250) bought this truck new, and it was my first vehicle. It's going to last me several more years until I'm able to buy a new or nearly new truck, so I want to make it into the truck I need. I'm fully aware that this is a pretty big job, I wouldn't even bother asking if I wasn't serious.

Back to the real issue, I think I'm going to hold out for a 5-speed truck. Plus, the wife recommends we postpone this project for a few months . Thanks so much for the info guys, it will get used!

 

WOW those are good prices. Anybody have a similar site for manual transmissions? WIT seems to only deal in autos. Didn't find much on ebay.

 

Everything will bolt right in,I`ve done several.sticking within each generation does make it easier.87 to 91`s are the same generation,if you are staying with the standard tranny, I`m pretty sure you can get away with just changing tailstock, not so with the automatic,the 4x4 rear-end could be limited -slip so you`ll wanna keep it, the rear blocks need to be put in with longer bolts and flex hose,or the front will sit high,I`ve put 4x4 extended cab systems in a short box step side,only thing I didn`t have was a drive shaft,had one made with the ends from one that fit, it cost less than 200.