1988 Bronco 2 Pre-build Check

[tolehouse]

I have an 88 B2 with just shy of 200k that is due to be rebuilt after several years of abuse. I'll probably tackle the build in stages, but wanted to run my plan by those with more experience to avoid any major pitfalls or save myself from drastically over building a particular segment of the truck. Use is a mix of pavement and off road in CO and the broader mountain west. Our group generally runs medium difficulty trails, but the lower half of 'hard' trails aren't uncommon either.

Current setup:
Engine: Stock 2.9L V6
Transmission: Mitsubishi FM146
Transfer Case: BW 1350
Front Axle: Dana 28
Rear axle: Ford 7.5"
Wheels: 15" steelies
Tires: 29" duratracs
Suspension: Very tired stock springs/leafs and KYB shocks

Planned build
Engine: Ford 4.0L v6 OHV, harness and dash from a junkyard donor
Transmission: no change
Transfer Case: no change
Front Axle: Dana 35
Rear Axle: Ford 8.8" w/ disc brakes
Wheels: 15" steelies
Tires" 33" TBD
Suspension: 4 or 6" lift kit (skyjacker or duff)
Body lift: 2-3"

Build Questions:
Engine:
Any common failure points on the 4.0 OHV I should be aware of, and replace before I put the block in?

Transmission:
Can the FM146 handle the tire and suspension changes? Alternate recommendations if not?
How difficult is it to turn a manual to an automatic? Have stalled a few times while crawling up/down steeper features and had to change pants. Automatic would alleviate this.

Axles:
Should I regear the axles to support the tire size and suspension changes? If I remember right, one of the usual ratios with 33s will keep the speedo accurate but that's an expensive reason to avoid some mental math if additional strength isn't needed.
Is putting Dana 44 knuckles on the Dana 35 worth the hassle?
Planning to weld the rear axle tubes as I understand that can be a point of failure

Suspension:
I know 2" body lift is needed to help fit the 4.0, but would a 4" spring lift still enable the 33s to fit or better to go with 6"?
Pros/cons of Skyjacker vs Duff?

Misc:
Saginaw power steering pump swap
R134a o-rings on A/C circuit
LED or HID headlights
Roof or rack mounted KC hi lites
High output alternator for lights, stereo, etc
Oil filter relocation
Head unit swap for Android auto
Change front seats from bench to seats with headrests (drop in donors?)
Rear bumper: James duff swing out rear bumper or DIY

Thank you in advance!

 

[rusty ol ranger]

Youll grenade a mitsu trans pretty quick with a 4.0. Youll want an M5OD

33's shouldnt be an issue with your planned lift

If you get 3.73 axles i dont think youll need to regear. If youre worried about speedo accuracy you can always change the gear on the end of the cable to account for the bigger tires and different gears.

The 4.0 OHV is pretty solid reliabilty wise. If going with a junkyard motor, its always wise to plan on a rebuild.

Im sure others will have more to add.

 

[rubydist]

If the 4.0 ohv was ever overheated, it was pretty likely to crack a head, so there is a good chance that your jy engine will have issues. As Rusty suggested, I would plan on a rebuild with some good aftermarket heads that are way less likely to crack - then you can use and abuse for a good long time.

My experience also says the transmission will need to be upgraded to the M5OD.

The B2 is not very stable to begin with, if you lift it 4-8" it will not like to go around corners.

 

[dvdswan]

Welcome to the site. Any pictures to start with?

 

[tolehouse]

Welcome to the site. Any pictures to start with?

Not sure who did the paint in the truck's 35 year history, but it brought a smile to my face when I found it on craigslist

 

[tolehouse]

Youll grenade a mitsu trans pretty quick with a 4.0. Youll want an M5OD

The 4.0 OHV is pretty solid reliabilty wise. If going with a junkyard motor, its always wise to plan on a rebuild.

Im sure others will have more to add.

Appreciate the input! I know the M5ODR1 came bolted to the 4.0 on some RBV. Is the M5ODR2 also compatible, or just overkill at that point?

4.0 will either be junkyard sourced and rebuilt, or purchased as a reman to let someone else do the rebuild

 

[tolehouse]

If the 4.0 ohv was ever overheated, it was pretty likely to crack a head, so there is a good chance that your jy engine will have issues. As Rusty suggested, I would plan on a rebuild with some good aftermarket heads that are way less likely to crack - then you can use and abuse for a good long time.

The B2 is not very stable to begin with, if you lift it 4-8" it will not like to go around corners.

I'm conscious of the B2's notoriety for instability even in stock conditions. Extended radius arms with the lift kit should help extend the wheelbase some, but I take care to go thru corners smoothly/gently. I may offset the wheels out slightly to further increase the wheelbase size for stability.

It sounds like the whole line of cologne v6 were susceptible to head issues then since the stock 2.9 came with your caution as well. Any recommendations on aftermarket suppliers for more robust heads?

 

[rusty ol ranger]

Appreciate the input! I know the M5ODR1 came bolted to the 4.0 on some RBV. Is the M5ODR2 also compatible, or just overkill at that point?

4.0 will either be junkyard sourced and rebuilt, or purchased as a reman to let someone else do the rebuild

I think the R2 only came in SBF bellhousing patterns, as in the 300/302.

It would be overkill.

Just curious...have you thought about just rebuilding the 2.9? Then you could probably keep the mitsu.

Disclosure though...im a 2.9 fanatic lol...so i have to ask.

 

[lil_Blue_Ford]

All right… so I’ve been down this road before…

Engine: The 2.9 can be a decent motor, especially with a rebuild and some tweaks, but IMHO, it’s no good beyond 33” tires. I ran a 2.9 in my choptop for a few years. Blew a couple up (head issues), but it did just fine. The last 2.9 I put in it ran really well and was still running when I pulled it. I pulled it to go to a 4.0 because when I went from 33’s to 35’s it just didn’t have enough. First through third it would pull hard only to fall flat on its face in 4th and OD was useless. A 4.0 resolved that, but I’ve blown a few of those up in it too. I’ve about had my fill of junkyard engines as a result. I want to rebuild a 4.0 to drop in there and go full at it, do balanced internals and free-floating rockers, cam, flow porting and all. Hopefully all of that work will result in something much more reliable than a junkyard engine.

Transmission: Everyone says the FM-146 won’t hold up. So far mine has, but when it goes, it’s getting an M5OD. It may be the fact that my choptop is rather light (relatively speaking) as to why it’s holding up. That and I can’t keep a motor in it because it has a penchant for eating them. The R2 as far as I know is a SBF bellhousing only, so will not bolt up. That said, I’m also not sure that the R2 is actually stronger. Maybe. But I ditched the R2 in my F-150 long ago in favor of a ZF5 and would never go back, so that kinda says my opinion on the R2, not worth the effort to try and mate it to a 4.0, especially when the regular M5OD can be found in newer Rangers (not sure what year they first appeared, but probably around 90 with the first 4.0 motors and I don’t believe they really changed up through 2011).

Shouldn’t be super hard to change to an auto BUT, your auto options are kinda limited. C-series autos are getting scarce. The common autos found behind the 4.0 is the A4LD and 4R44, 4R55, and 5R55. The A4LD is notorious for dying although they can be built up some. The 4R and 5R transmissions are the more electrically controlled versions essentially.

Axles: D-35 and 8.8” are solid choices. Not sure that doing D-44 knuckles are worth it. I didn’t do that on my choptop (I’m still actually running a 9” brake 7.5” rear in my choptop because I haven’t gone through getting an Explorer 8.8 with disks re-geared yet). I have broke front D-35 shafts though. Not the outers, but the shafts. Not really sure what to do about that except try cro-moly shafts. The D-44 uses the same U-joints and isn’t substantially beefier (plus it changes the bolt pattern for the wheels). You’re going to want 4.10, 4.56 or 4.88 gears. I’m currently running 4.10 in my choptop and it works, but a doubler would be nice.

Lift: so my choptop has a 2” body lift and about 5” of suspension lift and sits on 35’s. Cleared 33’s well with 5” of lift. Now, that said, my choptop is an 89 so it has larger front wheel openings in the fenders, so you’re going to need to either lift higher or trim the fenders. I’d probably trim the fenders.

Body lift may not be needed to clear the 4.0, but it does make working on things easier.

Suspension: Jim Oaks runs Skyjacker, so that should say something. My choptop is a mix of Duff and custom. Mine works, but I’m not super happy with it. I think it could be better, but the flip side of that is despite not being super happy with my lift, it’s stable and it works. Changing what I have may or may not work out to my satisfaction. At this point, if/when I experiment with changing, I may very likely try to find a way to make coil-overs work.

Tires: you’re going to want 12.50 wide tires (33x12.50-15, 35x12.50-15, etc). After lifting mine beyond 3” and running 33’s, I tried going back to 31x10.50-15 tires to wear out an old set. A quick trip around the block had me putting the 33’s back on because they felt way more stable. Go aggressive. Currently I have BFG AT tires on the front and MT on the rear. I’m not impressed with the AT tires. My next set is going to be all MT tires, most likely Mastercraft Courser MXT. Oh, and I’m running 12 psi because that got the tires to wear mostly flat on it, even on the street. 35 psi and I felt every pebble on the road and a chalk line drawn across the tread showed my contact patch was about 1” diameter in the middle. 12 psi and I’m wearing nearly all the way across the tread, much better ride and handling and has had zero issues on the street or off road from that pressure.

Power steering pump, well, I’m likely going electric in mine. If the motor is dead for some reason but the battery works, you still have full power steering which would be a huge help with big tires.

 

[tolehouse]

Rusty, I'd considered rebuilding the 2.9 as it's been good to me, but I fear that the added stress and weight from the rebuild and planned add ons will leave me wanting for more power. I may save it and rebuild it on my own time later, as I already have 2 Mazda/Ford L3-vdt engines in my garage awaiting rebuilds for my daily. One to keep as a spare and one to sell.

Lil_blue_ford, thank you so much! Your experience and feedback with your own setup is incredibly helpful. I really appreciate the input on tires and suspension. 12.5" wide tires will be a substantial contact patch increase from my ~9" wide 29s.

 

[Uncle Gump]

I bought my Bronco II with most of what you want to do already done. D35... 8.8... 6 inch skyjacker lift. No body lift though.

I'm leaning 33x10.50... because of the smaller contact patch anders rolling resistance for the 2.9L and FM trans. My plan is to run them on a set of factory Alcoa wheels. Plan B would be to put them on 15x8 with a 3.75 inch backspace if it feels unstable. There is also a considerable weight savings with 10.50's and aluminum wheels... always something that should be factored into the build process.

 

[rusty ol ranger]

Rusty, I'd considered rebuilding the 2.9 as it's been good to me, but I fear that the added stress and weight from the rebuild and planned add ons will leave me wanting for more power. I may save it and rebuild it on my own time later, as I already have 2 Mazda/Ford L3-vdt engines in my garage awaiting rebuilds for my daily. One to keep as a spare and one to sell.

Lil_blue_ford, thank you so much! Your experience and feedback with your own setup is incredibly helpful. I really appreciate the input on tires and suspension. 12.5" wide tires will be a substantial contact patch increase from my ~9" wide 29s.

If the 2.9s currently running good id do the lift, tires, and axles and try it out. It might surprise ya.

If its on its last legs then by all means do what ya wanna lol

 

[ryan]

i'd leave the axles with the 3.73s because you'll probably find them like that for the swap, wheel it, and then figure it out. in the same way rusty is a 2.9 fanatic, i'm a gearing fanatic and for any real wheeling i'd be looking at 4.56s even with 33s.

 

[lil_Blue_Ford]

Rusty, I'd considered rebuilding the 2.9 as it's been good to me, but I fear that the added stress and weight from the rebuild and planned add ons will leave me wanting for more power. I may save it and rebuild it on my own time later, as I already have 2 Mazda/Ford L3-vdt engines in my garage awaiting rebuilds for my daily. One to keep as a spare and one to sell.

Lil_blue_ford, thank you so much! Your experience and feedback with your own setup is incredibly helpful. I really appreciate the input on tires and suspension. 12.5" wide tires will be a substantial contact patch increase from my ~9" wide 29s.

You’re welcome. I tried to cover most of your questions, you’re welcome to ask whatever you want and I’ll answer as best I can. My choptop started as a 2wd with a blown up 2.9 from a former member on here. I converted it to 4x4 with help from a couple other former members and built it with the help of members on here. I did a 1.5/2” leveling lift first (Skyjacker coils and rear air shocks) and ran it on 31x10.50-15, then I got a deal on Duff axle pivot drops and 3” coils so that went on, but then I needed extended arms which got fabbed up by another member. It didn’t stay at 3” for long before I did custom Explorer leaf packs and extended shackles in the rear and added F-150 spring perches for the coils in the front and got myself to about 5” of suspension. I‘m a little fuzzy on when I did the 2” body lift, it was either before or after I went to 5” on the suspension. I was on 33’s for a bit on the full body and suspension but I went with 35’s after I did some work on a D-35 (bracing and plating, open the passenger beam window, ground the shafts for full circle clips and built new extended arms).

I was worried the wider tires would cause issues with traction for as light as the choptop is and I worried about brakes. Neither has been an issue at all. Stomp the brake pedal hard enough and it tries to throw you through the windshield. Tire pressure proved to be very important. Tire selection does make a difference too. The 33’s I ran were actually ancient bias ply tires, Ground Hawg knock-offs. The choptop was straight up point and click on those. I’m sad they’re worn out. I didn’t have enough weight to pull anyone, but I could go anywhere. The BFGs don’t work as good but they work ok. I got a good deal on them. I wouldn’t spend the money to buy new BFGs to replace them. The rears are still ok, but the ATs in the front are starting to dry rot so I’m about due for new tires.

 

[lil_Blue_Ford]

I bought my Bronco II with most of what you want to do already done. D35... 8.8... 6 inch skyjacker lift. No body lift though.

I'm leaning 33x10.50... because of the smaller contact patch anders rolling resistance for the 2.9L and FM trans. My plan is to run them on a set of factory Alcoa wheels. Plan B would be to put them on 15x8 with a 3.75 inch backspace if it feels unstable. There is also a considerable weight savings with 10.50's and aluminum wheels... always something that should be factored into the build process.

After running 31x10.50-15s on my choptop after lifting it and running 33x12.50-15, I would never put a 10.50 tire back on. The stability the wider tire gave was well worth any rolling resistance increase. Interesting enough, it felt the best running low air pressure, usually was around 12 psi, but really anywhere 10-15 psi. That gave me pretty much full width contact patch on the tires and very stable. The 31s I had to run harder and it was noticeably much more tippy feeling.

My choptop with the 2.9 and FM-146 handled 33x12.50-15 tires on steel rims just fine. It was the 35x12.50-15 tires on steel rims that it just didn’t like. The 4.0 handles those tires much better. I’ve been running 15x8 white wagon wheels on it. Could go to a 15x10 on the rims, but I wanted to tuck the bead inside the sidewalls to help protect the rims from rocks and stuff. Always wanted aluminum rims on it, but most of the RBV aluminums are 7” wide and that’s a bit tight and aftermarket aluminums haven’t been in the budget.