I'm letting the cat out of the bag...

[exilous]

I can't hold it in any more I just gotta tell you guys what my drivetrain will be when I am done with my C30 dump truck.

Engine: 350 bored .60 over Hope to be making close to 300 horsepower and torque
Trans: SM 465
Trans: 3 speed dana
Rear: 14 bolt 4:11 ratio

Yes thats right I am going to have 2 transmissions. It will be a 12 speed C30. Thats if I split it every gear I most likely will just split the upper and use 8 gears. There are no ratio tags on the 3 speed box but just eyeballing it when i popped the cover I believe it will be 1:.5 1:1 and 1:1.25. I think if i wrote that right I just looked at the yokes and put it in each gear and spun it around for 1 revolution engine in it did either .5 revs 1 revs and 1.25 revs out. I'm not sure if I did my calculations right or not, but I think I should be able to be topping out my speed at 3000 RPMs at 90 MPH if the ratios are correct and everything works out. I have a feeling its wrong but who knows. What do you guys think of the whole idea? I just want some feedback I'm doing this regardless. Thanks in advance.

[zieg85]

A good friend of mine has a 50's something Studebaker 1 ton dually maybe 1.5 ton who did that very thing except he used 2 4 speeds.  Runs great down the highway at 70, his rear end is in the 5's.  Looks tricky to drive but he has it down pat.  His problem is the brakes were never anygood when the truck was new but most of the time he is hauling a car trailer with electric brakes which helps alot. 

[exilous]

Very cool. Well for me shifting shouldnt be much of a problem I grew up with old mack trucks with 2 sticks, 15 speeds 20 speeds so I don't think this will be far from either of those.

[exilous]

Ok i have been doing some research and I found my transmission online. and it posts the gear ratios and stuff. Here is a link if you guys want to check it out.

http://www.truck-parts-auction.com/3-speed-Over-Drive-Spicer-Auxiliary-Transmission-OD-8031-R,name,112091,auction_id,auction_details

[choptop]

Sounds awesome! I love things that are a little out of the norm. Excited to see your truck done so I can see how it all works out. Been following it closely since you started.

[zieg85]

Are you planning on putting the aux trans in backwards?  That is what my friend did in his truck. If not I guess a 3.08 final drive is decent but I think your going to be above 3000 rpm at 90 unless you have really tall tires.

[exilous]

I think I have to do some more research on the auxiliary trans I have, I found a site that showed 7 different models of the transmission each with different or slightly different ratios so I have to do some serious looking to find which one mine really is. Most of the ones I have seen the over drive ratio was anywhere from .73 or .75 or.83 and the underdrive side was anywhere from i believe 1.77 all the way up to 2.38 i think was the highest.

As for mounting it backwards no it should be able to go right in the normal way, I should be able to get rid of my carrier bearing and have the driveshaft welded right to the slider that is left on the end of the trans, when my dad removed it from this old diamond rio dump truck he left all the yokes on and some tube so it can be modified, so on the front I will end up having like a6 inch driveshaft from the main transmission to the auxiliary and like a 3 foot shaft on the back end going to the rearend. everything should work out but i honestly have to try to weigh this trans cause today I struggled to roll the darn thing into the bucket of the backhoe, its gotta be pushing 300 plus pounds at least. it makes my transmission look small. It's kind of funny. I will get some pics up of the aux trans tomorrow.

[zieg85]

Sounds like an undertaking.  I want to get a Ranger unit for mine, weighs 80 lbs and goes between the trans and bell housing.  Supposedly you just have to move the cross member back 7 1/2" and shorten the rear drive shaft by that amount.  I just can't justify the cost yet.  Keep us posted.  I think the main thing to be concerned with is the drive shaft angle being right.