Builds Bunny: 40th Anniversary FZJ80 / 6BT / NV4500 build (4 Viewers)

[thegogglesdonothing]

Edited for clarity now that my 6BT/NV4500 conversion is complete, January 2016. I started by buying a very sweet 3x locked 1997 FZJ80 40th Anniversary Edition here on Mud, from @kvothe. He's a super helpful, friendly and generous guy, and I think we were both relieved at the ease of the transaction.

He and the truck's previous owner had invested a lot of time and money in making the truck pretty stout, and managed to keep it extremely clean. The truck's purpose for me is primarily as a weekend/adventure vehicle, but it gets heavy use. My wife and I are always going and doing something on the weekends: endurance races, XC/AT skiing, cycling, hiking, camping, fly-fishing or some combination thereof. We live in the high desert and are often up in the Rockies driving above 10k feet, so a turbo diesel makes a lot of sense. You try driving up Wolf Creek Pass in Colorado in a tired old petrol truck and see how it feels!

I did the Cummins swap with a few objectives in mind:
- way more power
- way more fun
- *somewhat* better fuel economy and thus, range
- much more compelling engine noises
- drive a 4x4 go-anywhere locomotive of a truck

I ended up buying the motor and transmission from a 1993.5 Dodge Ram 4x4, so I got a 12v Cummins 6BT with a P7100 injection pump and NV4500 5-speed, and had both the motor and transmission rebuilt with new internals. Had a whole saga with a certain supplier of diesel adapter components, but I'm tired of complaining about the guy so I'll just say that it was a lot of time spent in limbo, that he ultimately didn't deliver and that there was plenty of re-work to be done to what he did deliver. Good riddance.

1997 FZJ80 40th Anniversary

• thegogglesdonothing
• Sep 4, 2015

Mods so far
4" OME comp coils (front), heavies (rear) and shocks
35x12.5R16 BFG KO2s on stock alloys
Slee sliders (from PO)
ARB front bumper (from PO)
Warn MD1200 winch (from PO)
Slee 1st generation rear bumper
Slotted rotors all around / upgraded pads (from PO)
new OME steering stabilizer (from PO)
Gobi Ranger rack + rear ladder + Hi-Lift Mount
ARB 2500 awning
James Baroud Space Evolution RTT
Cummins 6BT / NV4500 conversion, 4k fuel pump governor springs
custom shift lever, dorky but awesome vintage Toyota shift knob
OEM manual transmission console and shift boot
Weathertech digital fits all around
OEM dashboard cupholder (!)
Wits' End accessory panel
Wits' End passenger side fire extinguisher mount
ARB 50 qt. fridge/freezer
PFran Led kit for all internal lights + reverse indicators (SWEET)
20" cheapo lightbar on front bumper
IBS Dual battery controller
Dedicated Wits' End ARB / Anderson plug power cable
Slee washer bottle relocate kit
Optima Redtop as second battery
OEM right side second battery tray
450w inverter
4x Bluesea dual fast-charge USB ports
Corbeau GTS II x2, with ass heaters
9011 and 9012 bulbs in place of stock 9005 and 9006

Plans (as of August 2017)
Ample Dynamat, replace rear speakers, add subwoofer and amplifier
Replace carpet kit
Drawer system, debating ARB or Trekboxx
37"s and necessary adjustments / trimming
3.73 / 3.55 diff gears, or t-case reduction gears?

 

[Mr Cimarron]

That's a great combo. What transfer case will you be running and who is doing the conversion?
Also think about getting 4" OME comp springs up front. The 2.5 probably won't cut it holding up the heavy Cummins.

 

[thegogglesdonothing]

Thanks very much for the tip on the 4" spring - I've been in "wait and see" mode once the whole swap is done. The Cummins plus the front bumper and winch is a LOT of weight.

As for the t-case, I believe the current plan is to use the stock case, plus a conversion kit from DieselAdapters.com. The 6BT itself is a rebuilt 93.5 12v - and the rebuild gives me a bit more confidence in the longevity of the motor. I realize a 150k mile Cummins can be thought of as "nicely broken in" but I'm going to be happy a new build, I think. I'm leaving the transmission as-is, so the standard AWD, and am also in wait-and-see mode about the gears. The PO had it re-geared to 4.88 by Slee, and I'm not sure that that'll be the right ratio with the Cummins and the 35" tires.

Somehow, despite working in professional auto racing in the ALMS / Grand-Am and now IMSA/WEC for most of my career as a marketing guy, I've never picked up any mechanical skill, so I'm leaving all the mechanical decisions to a mechanic friend of mine, Micah Garcia-Black here in Albuquerque.

 

[jfz80]

Cool build plans. Ill venture to say 4.88 is too much gear for that combo

Wish I was closer, I'd trade you for the stockers

There is also a 3.73 gear group buy thread. Not sure how its going

 

[Dirty Koala]

I have 4.56 gears in my 97 that the 6BT and NV4500 are going into. I plan to run 37" tires with those 4.56 and see how I like it. I suspect I will still need to re-gear back to 4.10 though.

 

[Wheelingnoob]

Any updates?

 

[Dirty Koala]

I have still have to write up my rebuild with the new mainshaft...but here are a few teasers.

 

[Wheelingnoob]

I have still have to write up my rebuild with the new mainshaft...but here are a few teasers.
View attachment 1148123 View attachment 1148124 View attachment 1148120 View attachment 1148121 View attachment 1148122

I need to do that with mine too. Just need to fuigure out if I'm staying Isuzu or changing to a 6bt.

 

[Dirty Koala]

Are you going with an NV4500/HF2AV regardless or motor?

 

[Wheelingnoob]

Are you going with an NV4500/HF2AV regardless or motor?

Yeah I have all the parts already. If I change engines it makes the NV4500 swap that much easier.

 

[Dirty Koala]

Yeah, you only have an adapter on one side of the trans then.

 

[Wheelingnoob]

Yeah, you only have an adapter on one side of the trans then.

Yep

 

[cjmoon]

wow 4.88 gears ouch, cummins are very happy at 1900rpm with almost no lost power. 3.54 gears are needed. that's what stock in cummins trucks pulling 10k+ trailers all day long. i run 35" tires 4bt so less power and am very happy. 4.10's were too low. i'm at 385 miles on this tank and just below 1/4 tank with traffic and town driving. 20% hwy. before the gears i was at 15-16mpg all the time now 17.5-20 around town. no long hwy trips yet but reports have 22-24mpg.

 

[Wheelingnoob]

wow 4.88 gears ouch, cummins are very happy at 1900rpm with almost no lost power. 3.54 gears are needed. that's what stock in cummins trucks pulling 10k+ trailers all day long. i run 35" tires 4bt so less power and am very happy. 4.10's were too low. i'm at 385 miles on this tank and just below 1/4 tank with traffic and town driving. 20% hwy. before the gears i was at 15-16mpg all the time now 17.5-20 around town. no long hwy trips yet but reports have 22-24mpg.

Thinking about going 3.73's if I go 6bt. Plan to go 37" tires next. Don't want to lose all my crawl.

It will be years after the actual swap though.

 

[cjmoon]

Ya if your planning 37" 3.73 prabably gets you to the sweet spot but for I truly expedition that's not very hwy friendly and expensive to replace

 

[mjosoba]

I'm tossed up between nv4500 and a442 for my 4BD2TC. Regardless I'd like to end up 255/85's. I'm thinking 3.73 or 3.54's. Still debating.

 

[Wheelingnoob]

I'm tossed up between nv4500 and a442 for my 4BD2TC. Regardless I'd like to end up 255/85's. I'm thinking 3.73 or 3.54's. Still debating.

I would recommend going nv4500. I was not overly haply with the 4BD1T and my a440. Just seemed to suck up far more power than needed.

 

[scottryana]

What's up with the Isuzu? I thought they were supposed to be pretty good little engines.

I need to do that with mine too. Just need to fuigure out if I'm staying Isuzu or changing to a 6bt.

 

[thegogglesdonothing]

Any updates?

The update so far is... it takes a long time to source clutch pedal brackets from Australia and to get modified t-case adapters back from vendors. The rebuilt motor and transmission are done, and the shop doing the work is, in theory at least, doing the actual swap this coming week. I've had to walk away from the whole process a little bit since there's zero I can do to speed it up and I'm not a patient person most times. The builder has been great though, and I'm happy for him to know that there's a growing line of other people behind me with 80s waiting for 6BT swaps.

I'll post up a bunch of photos of the truck once it's done.

 

[thegogglesdonothing]

wow 4.88 gears ouch, cummins are very happy at 1900rpm with almost no lost power. 3.54 gears are needed. that's what stock in cummins trucks pulling 10k+ trailers all day long. i run 35" tires 4bt so less power and am very happy. 4.10's were too low. i'm at 385 miles on this tank and just below 1/4 tank with traffic and town driving. 20% hwy. before the gears i was at 15-16mpg all the time now 17.5-20 around town. no long hwy trips yet but reports have 22-24mpg.

Yah, we're in "wait and see" mode with the gearing. I don't anticipate ever towing, but will have plenty of extra weight with the 6bt, bumpers, roof rack, drawer system and all the other crap that gets accumulated. The PO only re-geared the truck less than a year ago, I believe, and Slee did all the work, so having to drop another couple grand on new NEW gears is going to be a bummer, but it is what it is. Good news is, I'll have a lightly used set of 4.88 gears to sell here on Mud some day!