Recommendations for 4.0l swap in BII

speedworks101 · Dec 4, 2010

Hey guys, I'm new to this forum. I recently picked up an '87 Bronco II with a lift 6 in. Skyjacker lift in it. It is a 2.9l with automatic tranny and manual transfer case. With the 2.9l it is a little underpowered. And judging from the reactions of some guys who've done the 4.0l swap, I really want to go this route. I have a couple questions. What year 4.0l would you recommend for simplicity? Will it bolt to my existing transmission and work well?
If it is actually better to do the full drivetrain swap what is the recommended list of donor vehicles M/T and A/T?
I'd like to keep this B2 because the body is very clean(no rust) and it is just a cool lil rig.
I'm no stranger to gettin' dirty, just need a good solid base to start from before I tear into it. Thanks. I'll post pics after a little research and have the parts or donor vehicle to start this project.

99RangerKrazy · Dec 4, 2010

I've seen the swaps done in pre-1989 BII's, so it's doable. However, it appears to be easier in 1989-1990 BII's because of the big bulkhead (canon, I think it's called) plug on the firewall. This didn't come until 1989. But it's definitely still doable for a 1987.

Transmission: Will it bolt up? Yes. Would I do it? No way. I've killed an A4LD (your tranny) with the 2.9L with only 5,000 on the rebuild. The 4.0 would shred it. I'd highly recommend swapping over to the M5OD manual tranny that came behind the 4.0 from the factory. Much stronger and reliable.

Also, if you have any tires larger than 31s-ish, you'll want to have the Dana 35 front axle and not the Dana 28. The Dana 35 is immensely stronger than the 28.

That should get you started. I'd definitely read a little more about the 4.0 swap into pre-1989 BII's.

bobbywalter · Dec 4, 2010

91-92 is easy.

country0001 · Dec 4, 2010

When you do the swap,get the whole truck to use as a donor. Use the dash,harness,steering column, engine, tranny, and t case. Craigslist is your friend.I've done one swap into an early 90 B2. I'd rate it a 6.5/10 on difficulty. Have a buddy to help and allow plenty of time, it took me 2 months to complete mine, but factor in kids rain and baseball. Probably 7-8 days of total work. Could have one done quicker now that I know how. Good luck, take lots of pics and start a build thread.

bobbywalter · Dec 4, 2010

country0001 said:
When you do the swap,get the whole truck to use as a donor. Use the dash,harness,steering column, engine, tranny, and t case. Craigslist is your friend.I've done one swap into an early 90 B2. I'd rate it a 6.5/10 on difficulty. Have a buddy to help and allow plenty of time, it took me 2 months to complete mine, but factor in kids rain and baseball. Probably 7-8 days of total work. Could have one done quicker now that I know how. Good luck, take lots of pics and start a build thread.

takes me 15-30 hrs depending on how big of a rusty pos it is and longer if i am not at my shop with my tools.

i would call it a 4 for obd1

and potentially a horror story with obd2....just depends on your tuning resources.

pretty hard to get me to use anything but the eec harness.

Andres629 · Dec 4, 2010

I'm gonna keep an eye on this. I've got an '87 but want to keep the pre '89 dash.

bobbywalter · Dec 4, 2010

i dont like anything but the gen 1 dash :icon_thumby:

speedworks101 · Dec 4, 2010

Thanks guys. I intend on keeping the gen 1 dash. I've scoped out a couple donor vehicles on craigslist. I found a 1991 ranger with a 4.0l and 5spd, looks like a good donor canidate. Hopefully the guy still has it, I'll call tomorrow. I picked up the Chiltons manuals for both rigs to get wiring diagrams. Just need to get a shop secured and donor rig and I'm off and runnin'.

country0001 · Dec 5, 2010

Definitely start a build thread

disciplerocks · Dec 5, 2010

Just picked up a donor myself. Cant wait to see your progress.

84bluebronco2 · Dec 5, 2010

Good luck man!! You will do fine if you take your time and exchange everything that country 1001 mentioned. I almost hate to see a 92 ranger get gutted lol. The 83-92 rangers are my absolute favorite trucks, and I've always wanted one with the 4.0 or even a 2.9. My expo is sating my thirsts for now though. Keep us posted, make a build thread, take your time, and TAKE TONS OF PICTURES!!

Shran · Dec 5, 2010

Hey man, how's my old B2 treating you?

I think you should do the 4.0 swap. I was going to and I even had an engine lined up at one point but you saw how many other projects I have right now.

Hahnsb2 · Dec 5, 2010

Basically get the wring diagrams and look at the 4.0 harness and see what needs to be done to basically make it standalone and wire it up. I kept my Gen 1 dash, the wiring wasn't really too bad and I used a 94 engine. 91-92 are simpler.

59bisquik · Dec 6, 2010

I swapped a 91 4.0 into my 86 with an A4LD.

I had to get a 4.0 A4LD torque convertor since the stall is different from the 2.9 to 4.0.

I used the stock 2.9 motor mounts, y-pipe and exhaust.

I got the entire sploder as a donor vehicle. I kept my stock dash and just adapted the harness. With a manual for each, it was pretty simple to modify the harness.

The upgrade was well worth the hassle. More power and better fuel mileage.

I push 35's with 4.88's and the power between the 2.9 and 4.0 is pretty noticable.

Recommendations for 4.0l swap in BII

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