www.ColoradoClassicBroncos.com

I've been talking bout doing some serious work to my 68 for a while. Now its time to actually start. I have an new wiring harness, a 5 speed (M5R2), a transfer case rebuild kit, and last but not least a 4BT to install.

Its not a bad truck as it sits but, those are just the major things I want to change, little things like the dashboard, seats, door panels and, a more family friendly roll cage are going to happen too. I've been systematically making room to get it in the garage with space to work around it and started gathering the tools I don't have already for fabrication.

I know there's a wealth of experience here and look forward to receiving input and picking your collective brains as things progress. I also plan on finding time to get to more of the breakfasts since I only made it to the one a the Platte River Bar and Grill so far.

Not sure that will be a good combo.
The 4BT makes a lot of torque and the M5 series transmissions are known to have low torque limits.

I'm a fan already, you have a clean starting point and you are more than welcome to check out my 4BT swap in person. I have no personal experience with the M5 but there is a dude on Expedition Portal that is running that combo in a bump side crew cab and he likes it. He said the gear ratios are diesel friendly, his truck is not a monster power or size wise, so your milage may vary. I'll dig up a link to his build.

Here you go, he has some really cool build ideas and you can tell he uses his rig.

http://expeditionportal.com/forum/showt ... p?t=110920

Nice rig, looking forward to the build!

Subscribed! mmmm diesel!

I've done a lot of digging around and contemplation about the transmission. There are a couple of them out there running the M5OD, my thoughts are that if the M5 breaks, a ZF is the same length and bolt pattern on both ends so it'll be a direct swap. The engine I have came with a Ford adapter plate and a Borg Warner T19. How much of a liability do you think the Dana 20 will be? I only plan on doing light wheeling, and towing a small camper, 3000lbs. ish with this truck in the end.

The biggest problem, that I've had, is the way the 4BT torque hits. There isn't a lot of it, 335 ft/lbs on my factory P pump/CAC motor, but it's like two hammers. Think bang bang...bang bang...bang bang. So it'll find your weak points in the system. I think the D20 will hold up fine if you wheel it moderately, but if you ever ask it to pull out of a deep spot and get on it hard it'll twist the rear output shaft clean off. I'd upgrade the rear output shaft and make sure that you're in 4wd when you put it in a tough spot.

What version of the 4BT do you have? I'll guess a VE pump that may or may not have a water jacket after cooler based on the Ford repower.

The D20 is a pretty stout little box. I can't attest to towing with it, but light wheeling shouldn't be a problem.

kinder wrote:The biggest problem, that I've had, is the way the 4BT torque hits. There isn't a lot of it, 335 ft/lbs on my factory P pump/CAC motor, but it's like two hammers. Think bang bang...bang bang...bang bang. So it'll find your weak points in the system. I think the D20 will hold up fine if you wheel it moderately, but if you ever ask it to pull out of a deep spot and get on it hard it'll twist the rear output shaft clean off. I'd upgrade the rear output shaft and make sure that you're in 4wd when you put it in a tough spot.

The M5 (heavy duty version) transmission is rated 330 ft/lbs max, so stock the 4BT is over by a little plus the sudden impact.

Maybe a good idea to start saving for a ZF.

I know the guy from expeditionportal, he is also on FORDification.com (a bumpside forum) he seems to be a careful driver off-road.

Yeah the Torque on those engines peaks at 1500 RPM, totally different power band than V8's so I can see how that might apply a bit of shock load depending on what you're doing at the time. I saw you (Kinder) are working out the weak links in your drivetrain as we speak. I would definitely like to check out your ride, I live in Aurora and run down to Parker to work out at least twice a week. I had a picture of my engine tag on my phone but, it mysteriously disappeared. I tried to look up some info through the Cummins but found better luck in the 4BT Swaps site in the end. I have a VE Pump apparently, didn't realize this at first but the engine is rated at 120HP. I picked it because it was clean for a box truck engine and runs well.

The VE motors aren't that far behind the P motors in the hp/torque numbers, like 30 ft lbs if my memory is right, and that was factory fresh. I think you'll be fine with the M5, you can get them cheap from PnP all day long, grab a spare and set it on the shelf.

I'm on spring break this coming week, shoot me a pm and we can meet up.

If you do use the M5 make sure that you replace the three plugs at the back of the shift rails with something more durable, such as freeze plugs.

The rubber plugs the factory used are known to go bad/fall out and then the oil is pumped out, your transmission runs dry, then you need another transmission.

Thanks for the tip on that, I planned on replacing the key seals and opening the top up to check things like shift forks before I put this thing in. I'm all for avoiding preventable problems.

Some 4BT discussion going on at CB:

http://classicbroncos.com/forums/showth ... p?t=251563

Some of those guys don't think the ZF is enough for the 4BT

sykanr0ng wrote:Some 4BT discussion going on at CB:

http://classicbroncos.com/forums/showth ... p?t=251563

Some of those guys don't think the ZF is enough for the 4BT

I'm going to say the ZF is plenty for the 4bt. Ford put the zf behind the 7.3 turbo powerstroke. Surely the powerstroke has more torque and hp than a 4bt. I really hope the ZF is all I've heard it is, I'll be helping my uncle install a zf behind a well built 514 cu.in ford big block soon.

I can only speak from personal experience and what has worked so far in my build. I pulled my zf from a '98 F350 and it had 289,000 miles on it, I was able to shift it prior to being pulled, but not drive the vehicle. And besides the syncros being worn it has been trouble free since I put it on the road in 2013. It's weakness for me has been the internal slave, I'm on the 3rd one. I don't baby my Bronco, it's my preferred daily driver, my off road rig, my hunting rig and my go get a ice cream rig. This morning it pulled ~4000 lbs from the Springs to Franktown. I'm sure I'll post up when it finally won't shift, but until then I'll keep grabbing the gears and listening to the turbo spool.

crawlercreations wrote:

sykanr0ng wrote:Some 4BT discussion going on at CB:

http://classicbroncos.com/forums/showth ... p?t=251563

Some of those guys don't think the ZF is enough for the 4BT

I'm going to say the ZF is plenty for the 4bt. Ford put the zf behind the 7.3 turbo powerstroke. Surely the powerstroke has more torque and hp than a 4bt. I really hope the ZF is all I've heard it is, I'll be helping my uncle install a zf behind a well built 514 cu.in ford big block soon.

It seems to be that "bang-bang" torque hit of the 4BT that does the damage in their opinion.
Much the same as even a small impact wrench will do things a six foot cheater bar will not.

They're not wrong. The "bang" delivery of the torque is significantly different than a gasser V8. That said, they did put them behind a powerstroke, which likely has as much "bang" per cylinder and double the frequency of delivery. I have a hard time thinking that the ZF can't handle a stock-ish 4BT.

I didn't say I was the one that thought the ZF5 was not strong enough.

I do have reservations about the M5od standing up to the beating.
It is borderline for that much torque without the impact.

I see what you're talking about, when you do the math, 3.9L / 4 cylinders means pretty large cylinders making the torque of a V8 with twice as many cylinders and a much smoother output. I'll plug in some numbers on the drivetrain ratio calculator and see if the NV4500 might be worth while. Am I correct in assuming a Dodge version wouldn't need an adapter for the engine? This way I can do an external slave and maybe avoid an adapter if I put a NP205 behind it.

I think the Dodge NP205 will be passenger side output, Bronco is driver side as are all Fords.

Your 4bt had a Ford trans right? If so you'll have to swap the adapter plate to a Dodge adapter plate, and luckily there are more of those than Chevy or Ford. It's also important that it's a 1st gen Dodge plate that came on the 12v, and possibly the 24v plate will fit, you'll need to read up on it to confirm. Advance adapters make adapter to go from NV4500 to Ford 205. http://www.advanceadapters.com/products ... sfer-case/

Edit: This looks interesting, I didn't follow the links in the thread but this guy was trying to mate them up without an adapter. Using the Chevy NV4500 output on the trans and input on the 205.