Diesel engine for rock buggy?

[GO 4LO]

I've got a big set of axles and tires that I'm going to be building a trail buggy out of.

After getting the tube chassis built, I've been thinking of using a mid-mounted diesel motor, so I've been debating between the 4bt and the 6bt. The axles weigh around 2k lbs together. Tires are around 400 lb each, and wheels are 125 each. So unsprung weight alone will be in the 4k lb range.

Due to the high weight, I've been leaning toward the 6bt - what do you guys think - 4 or 6?

Chris

 

[BJMarshall]

I can assure the 4bt will suffice. I t will save you a little weight as well. I would like to see it with a 6 in it though.

 

[Forrest Nearing]

gotta figure they're gonna cost you about the same, so why not go for the gusto?



Forrest

 

[Dieselnutz]

Go for the 6!!!

 

[towner]

go with the 6bt but tell me when your wheeling so I'm not stuck behind you

 

[SRadke]

The 4 will have all the torque you need but they don't run as smooth and nice as the 6bt. What are you using for axles/tires at 1000/400 each? Starting to sound like stump puller not a trail buggy.



-Scott

 

[JBurghard]

Whats this somebody steeling my idea???



I have in the works to use a 6bt with a th400 and a 203/205 doubler running 2 1/2 ton rockwells with hummer wheels.



If you wanna talk some more on the details let me know.



Wanna have it built by EJS next year.



James

 

[GO 4LO]

The axles are big planetary axles - they run about 900 lbs each, have a 10-ton payload capacity each, 16. 65:1 gearing, 19" discs. Wheels will be custom 26" double beadlocks with 28L26 combine tires. Realistically, this vehicle will probably be more useful in the mud than on most trails, due to the size. I've got a TJ on Ford 9's and 40's for tighter trails and am currently building a TJ on Unimog axles and 52's. Just wanted to try something different . Thanks for the input, everyone.

Chris

 

[Hudsonhawk]

Sounds like one heck of a rock buggy. But you ae definately going to be WIDE for some of the trails I have been on.

 

[BJMarshall]

If you plan on spinning those big tires in the mud, you better go with the 6, and paln on BOMBing it pretty good.

I need to see some pictures. Have you got a good source for Mog axles?

 

[GO 4LO]

Originally posted by BJMarshall

If you plan on spinning those big tires in the mud, you better go with the 6, and paln on BOMBing it pretty good.

I need to see some pictures. Have you got a good source for Mog axles?

Overall width is going to be 101" - 101. 5" - technically it would be legal onroad if the tires were DOT approved. Still way too wide for most trails around here, though. Gonna have to get up to Attica where there's some open ground to test her out.

I have a friend in KY who runs across a set of Mog axles every once in awhile. I'd bought some 2. 5 ton Rockwells from him originally for my '97 TJ, but changed my mind and sold those. I'm going to have him keep his eye out for me. You looking for a set too?

Chris

 

[SKargo]

4BT most definitley! Weight is the enemy here. My friend Wayne who owns UpNOver is doing a 4bt landcruiser. Are you competing? My cruiser is going into the shop for a 4 link suspension this week.

 

[BJMarshall]

I would love to get set of Mog axles at a reasonable price.

What are the axles you are using sourced from?

What is the height of those tires? The're 50+ inches tall aren't they?

 

[GO 4LO]

Unfortunately, I won't be able to compete in any of the normal rockcrawling series, since they all require DOt-approved tires. I've heard through the grapevine that Four Wheeler is dropping their 'must be street-legal' clause for Top Truck Challenge next year, so I may try to get it done in time for that.

The axles I'm using are out of an all-terrain forklift. The tires are 64" tall by 28" wide, and the rims I'm having built are 26" dia, 20" width double beadlocks from Stazworks.

The Michelins I'll be running on my '97 TJ are 52" tall by 16" wide and use a 20" rim. I might consider competing in this one, since these tires are street legal. Right now, I've got a 302 sitting in the engine bay, but may end up going 4bt on this one .

Chris

 

[BJMarshall]

That sounds like the tire on a 10 ton Military truck (HEMTT)

16. 00R20

You are going to need the double bead locks. You will need to run less than 5psi. With no more weight than you have they will still probably stand up like they are full. Sure you already knew that. What Transmission and t-case are you looking at? With those planetary axles, you shouldn't have to worry about breaking anything. I would definitely go with the 6 with 64" tires, but the 4bt would be right at home in the jeep with the 52's. Fix your sig to show where you are located. This would be worth a long drive to see.

 

[LAlessi]

i believe the michelins are dot approved

 

[ISh]

I'd say an 8. 3L

 

[BJMarshall]

Yeah with twinsOo.

 

[GO 4LO]

Yup, you're right - the Michelins are DOT-approved, so they will be okay for competition. They are 16. 00R20 Michelin XL's. It's the 64" Firestones that aren't DOT-approved .

BJMarshall, you're right on the pressure - the sidewalls are 1. 5" thick!

I've thought about an 8. 3, too. The main problem seems to be finding anyone to build a transmission to handle the power. One of the bigger Allisons would be fine with a stock motor, but with twins and stupid pump, I might be in trouble, even with a relatively light vehicle.

Not 100% sure on trannies and tcases. I'd been planning C6/205 to go behind the 302. If I go Cummins, maybe 727/205 or even 727/profab? I'd like to keep it automatic. My '99 has a 5-speed, and I'm ready to try something different .

Chris

 

[BJMarshall]

I've got a TH400 in the bronco. It's working pretty good so far. I'm looking at a built 700 for it now. Suncoast said they would build me a converter. TCI has a sweet valve body for the 700 with full engine braking and the ability to lock the converter in first gear. Should work great for my application. I can't imagine the weight of the TJ being that much more than the Bronco. If I'm not mistaken, you have the ability to run the c-6 on the 4bt as well. Benny Avant (Avant Salvage) told me that, but I've never seen it.

Cincinatti is a long ways from here, but I'd still come and see the rock buggy