I currently have a T170 drive axle with a 6.50 ratio. I'm looking to swap it out for something with a higher ratio, preferably around a 4.10. My trans is a SM465 with a granny gear. I have a flat bed that is 91" wide. I have talked to several people locally and seem to be getting different answers but not from anybody that has actually done a swap.
1) Do I need to stay with drums in the back since I have drums up front? I was told I could use a proportioning valve and dial the back down a bit if they were discs. 2) Has anybody ever used a Dana 80? I've seen some with GAWR as high as 11,000 pounds 3) I plan on going from my current 20" dually wheels to 22.5 dually.
I want to try to accomplish this all while keeping the tires tucked under the bed. If anybody has any suggestions, I'll take them. If I'm completely off my rocker, I'll take that advice too.
Ok- - - - -first question- - - -is the end product going to be a real truck or a Cowboy Cadillac? There's a reason a rig with a 1.5 ton rating and most likely a 235 engine has a low geared rear axle. Getting a full load moving, and climbing hills at more than a snail's pace in 1st. or 2nd. gear is going to need some gearing down somehow. You might be better off finding a Brownie auxiliary trans with an overdrive ratio and turning that 4 speed into a 12 speed. You'll have a better top end without losing the ability to haul stuff. If the heaviest thing it's going to carry is a Yeti cooler and a few lawn chairs on the way to a tailgate party, go ahead and gear it up, but please get the steering, lights, and brakes up to par before you try to keep up with traffic out there on the Super Slab!
Once you learn to do the gearjammer's dance with two shifters, you'll be able to impress all your friend, also!
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Hotrod, Somebody before me dropped a 327 in it. I use it to haul our quads around. I'm not looking to scream down the highway at 75mph. Right now, it's screaming at 3000 rpm to do 50 mph. My goal is to get the rpm's down so I can drive it a little further than across town. So, to answer your question, it is still being used as a truck but probably not how it was originally intended to be used. --Steering box is being rebuilt this winter --Light all work --Brakes all work but that was part of my question with the axle swap
Have you thought about a trans swap? Clark had some OD models. An NV4500 may work too.
As far as rearend swapping. I can’t say if you’ll find the same bolt pattern, but an Isuzu NPR rear may work. They had gear ratios up to 3.54 down to 6.17.
The likely axle swaps with same bolt pattern and better gears are Dana 70HD and 80 from GM 3500HD and P30 or similar chassis. They all have disc brakes, and a vehicle with rear disc should also have front disc.
I have the 70HD (from an RV) in my 2 ton, and 22.5” wheels.
Whitedog, I ended up finding a NV4500 for cheap that was in a GMC 3500. After selling the truck it was in, I almost got the trans for free. That'll give me a 27% OD and bring the RPM's down quite a bit while tooling around town. Just ordered the bellhousing I need. Now if it would just stop snowing in Illinois and warm up a little bit, I could get this project started.
