Contemplating a Bobber! To do or not to do that is the question!

[Gunfreak25]

The axles and driveshafts are not the problem. The GMC's Hydramatic had a 15.67:1 low range reduction that applied nearly 4200lbs of input torque on each drive shaft. This much torque and it does not take a lot of binding in the system such as a log or large rock under a wheel to create twisted driveshafts. Shock load is also another factor in broken shafts but this is not a real issue with the 302 and low ratios.

Reverse low range was actually 17.35:1 which is just insanity IMO. One of my rear axle shafts has the splines slightly twisted in the reverse direction. Crazy stuff man!

When are you going to post pictures of your progress? opcorn:

 

[Section8]

Ok! Here is a little up date.
I haven't had much time to do anything with my rig. Didn't think you all would want to see pics of just repainted stock rims. Though it does drastically make the ol' M135 look a **** sight better than it was.
Temps have been pretty cold here at -25 to -30 Celsius. Makes it a bit miserable to work on the rig out doors.
On the up side!!
I posted my 82 sportster with a bunch of after market parts for sale or swap on another internet site, k...I for the city closest to me. Stating swap/trade or cash for a suitable motor tranny for my rig.
Posted it yesterday and already have 3 people wanting to swap their motors and trannies.
Option one: 318 with a 5 speed manual
Option two: 5.9 cummin with a 5 speed manual
Option three: 4bt marine with Allison auto.
Didn't think I would have such a choice. Thought I would have been luck enough just to have some one offer their suzuki swift.
Now I would like some input from you experts!!
Which would fit the easiest. Which would be least expensive for fab purposes. Which would be my best bet in general!
Your input is always highly valued!

 

[Gunfreak25]

Both Cummins have rear oil sumps so oil pan clearance should not be an issue. Both cummins are great engines (nuff said) but will be very expensive to repair or modify in any way. If the Allison is direct drive you will be limited to 45-50mph. The torque converter will help with not having a low range gear. For the 5 speed, the OD will be a god send. Make sure there is room to hang a clutch pedal. The 5.9 will need part of the firewall removed and a small doghouse mad in the cab for it. This is really easy to do actually. The 318 will be the cheapest to mod or repair. No injection pump to contend with. Power will be good and if the transmission has an OD that would be a great combo. Mileage will be about 10mpg max.

Really all good combo's just think about what you want to use the truck for as one will always work better than the other.

If it were mine i'd jump on the 5.9 like a $2 hooker regardless of cost. The engine that is, not the hooker.

 

[nattieleather]

Decisions decisions....what's a guy to do.... I say skip the 4bt because it's a marine motor which means you will have to modify it for street use. 318 is gas and Chrysler so it wouldn't be proper to put into a GMC... The 6bt sounds the best so far and is a strong motor. But if your not in a big hurry maybe wait and see what other offers you get. I always thought the IH six out of a truck or bus would be a good motor to use.

 

[panhapp]

SECTION8 You're not talking about a 8v-71 Detroit (318 hp) are you? Thats a lot of engine. I have a 4-71 that I think may be to heavy for the GMC.

Pan

 

[Section8]

I am really considering the 5.9 cummins.
My biggest issue is the length.
My measurements may be way off but from what I measure I will have to make quite the deep doghouse in the cab to make it fit.
I see that GUNFREAK has a M211 with a 6.2 in his, but I wonder if the engine bay on the M135 and M211 are smaller than a lot of the guys with the M35a2 that are running the 6bt's .
I just don't want to go and swap my harley for a motor that I am in the end going to hate because it will cramp my leg room or make the pedals tight for proximity. Not the kind of truck to hit the accelerator instead of the brake in!!
Gonna have to go out and measure again for the hundredth time how big the old 302 is and compare to what the 6bt specs are online.
Of course if the guy would be willing to swap the manual 5 speed for the auto allison if it isn't direct drive, no cluth to have to worry about!!!!
The 318 is the chrysler motor not the Detroit 8v-71.

 

[Gunfreak25]

That would be cool, the 6bt with the Allison. The M135's and M211's are the same bumper to bumper, only differences are bed width and the wheels of course. The M35's front ends are over 1 foot longer to accommodate the mighty Multifuel.

Back when I thought I would be going with a 5.9/G360 out of a 92 Dodge I took some measurements too. The doghouse will extend into the cab several inches, it will not interfere with driver leg room but it will decrease passenger leg room a little bit. Atleast no more than the big ol GMC shift tower sitting in the middle of the cab. Which would be omitted of course.

Looking forward to hearing what you decide to use!

 

[Section8]

Crap!! Talked to the fella with the 5.9 cummins.
Found out that it is a 4x4 dodge he has sitting at his shop.
He thinks that the transfer case is mated to the tranny. Ugh!!
I don't know if you can remove the transfer case on those or not.
The up side is he will give me the whole truck for my bike, which means I will be able to keep the wiring harness and such for my build!!
Down side is probably having to find a tranny to mate to the 5.9!!!

 

[Section8]

Talked to the guy with the engine again.
Another bonus!! He will throw in an allison auto tranny he has sitting around with the 5.9 and 5 speed. He is gonna take the motor and tranny out of the truck since he is 5 and a half hours drive and a ferry ride away.
Gonna meet half way and swap.
Says he may even be able to make a flex plate for the auto allison if I need one since he runs a machine shop.
Just hope he doesn't decide to back out!!!

 

[Section8]

Don't know if my progress pics are gonna work but here it goes for what it's worth!
Wheels before and after being stripped and then repainted.
Sorry not much else. Bumper is currently receiving same treatment.

 

[nattieleather]

is the Cummins motor hooked to an auto or a stick transmission? If it is auto then I would put the whole engine, trans and transfer into the truck. Move the GMC transfer case back and use the transfer case from the dodge to give you high low range. If it's stick then well.... either put a hydro clutch in or adapt to the cummins motor, which you should be able to find adaptors on line since that is not an uncommon set up.

 

[Section8]

Its is the standard five speed tranny that is attached to the 5.9 cummins.
The guy is willing to give me an automatic allison tranny with the other motor and tranny set up.
I will have to find an adapter plate if I decide to got the auto route.
Still waiting to hear from him on whether or not he wants to commit to the swap for my Harley.
I sure hope he does! Might be able to get the ol' girl running this summer!!
Keep your fingers crossed everyone!!

 

[Broke Down]

I am really considering the 5.9 cummins.
My biggest issue is the length.
My measurements may be way off but from what I measure I will have to make quite the deep doghouse in the cab to make it fit.
I see that GUNFREAK has a M211 with a 6.2 in his, but I wonder if the engine bay on the M135 and M211 are smaller than a lot of the guys with the M35a2 that are running the 6bt's .
I just don't want to go and swap my harley for a motor that I am in the end going to hate because it will cramp my leg room or make the pedals tight for proximity. Not the kind of truck to hit the accelerator instead of the brake in!!
Gonna have to go out and measure again for the hundredth time how big the old 302 is and compare to what the 6bt specs are online.
Of course if the guy would be willing to swap the manual 5 speed for the auto allison if it isn't direct drive, no cluth to have to worry about!!!!
The 318 is the chrysler motor not the Detroit 8v-71.

i have a 12 valve laying on a pallet in my shop, would you like me to get you a measurement? the conversion won't be very hard, you have a choice of transmissions as long as you have the right adapter plate. fyi: a 4BT adapter plate can be used on a 6BT if you find something you like there. there were a ton a bread trucks and UPS trucks that used auto and manuals.

 

[Gunfreak25]

Moving the GMC transfer back is actually not as hard as some make it out to be. Just redrill the holes in the mounting bracket on the frame, then weld on some secondary brackets to take care of the other two bolt holes that are now too far back to reach the OEM mount. The handbrake would still function as all you'd have to do is lengthen the little linkage rod that actuates the handbrake cam. The transfer case IN and NEUTRAL lever would not work without modifying the linkage, but I see no reason to as there's no reason to take it out of IN anyway unless flat towing the truck.

 

[hendersond]

I believe you may want to shift the transfer to neutral if you are using the winch to pull something else and you do not want the truck to drive. If you have a winch.

 

[Section8]

I have no winch to worry about, yet! Might just go with an electric one at any rate if I do. Save the hassle of trying to make a pto drive off the 5.9 and such.
BROKE DOWN if you could shoot off some quick measurements that would be great! I seem to be getting different numbers every time I google the 12v 5.9's specs.
Once I finish redoing the front bumper I think I am either going to give my windshields a redo or start dismantling the old 302 to make way for the 5.9, provided the guy doesn't back out last minute.

 

[Broke Down]

I have no winch to worry about, yet! Might just go with an electric one at any rate if I do. Save the hassle of trying to make a pto drive off the 5.9 and such.
BROKE DOWN if you could shoot off some quick measurements that would be great! I seem to be getting different numbers every time I google the 12v 5.9's specs.
Once I finish redoing the front bumper I think I am either going to give my windshields a redo or start dismantling the old 302 to make way for the 5.9, provided the guy doesn't back out last minute.

the variance in measurement is due to what the engine application is and if it is equipped with and components on the front. i have an engine with a front case and rear adapter on it, i'll measure it tonight if i remember.

if you need some help with the cummins side of things pm me and i'll link you a place you can go for some more info. these are very easy engines to maintain and fit, i think you will enjoy it.

 

[nattieleather]

or start dismantling the old 302 to make way for the 5.9, provided the guy doesn't back out last minute.

Well even if you go with a different motor than the cummins you still need to get the old motor out of the way....so eitherway that's a task that needs to get done.

 

[Broke Down]

You will have between 36-38" without the fan you need to have out of the way, that is rear of the block to the water neck. The valve covers will be a few inches shorter in length, I didn't get a height or width, it was dark and it's late...lol. I can measure more if needed, just let me know what you need.

 

[Section8]

Thanks BROKE DOWN. That was roughly what I was thinking the measurements would work out to be.
I am not so concerned about height. The engine bay is pretty deep from hood to frame rails.
Being a inline 12v 5.9 cummins is shouldn't have to many width issues either, I hope.
Just depends on all of the accessories on the motor I guess.
Thanks again for the quick measurement!!