Gmc 302 to sbc 350

[94cummins12v]

I'm wanting to throw a 350 sbc in place of the 302 gmc online six it has a 5 speed manual trans behind it curious if the trans from the 302 will bolt up to a sbc 350? Or just throw a sm 465 behind the 350 as well

[MARTINSR]

302 Jimmy and a 5 speed going to a SBC?

Brian

[94cummins12v]

Ya the truck has a blown gmc 302 in line 6 that I'm wanting to throw a 350 in its place but not sure if it will bolt up to the 5 speed that's currently in there or if I just throw a sm 465 behind a 350 and drop them both in

[OrrieG]

T-5?? What year truck??

[94cummins12v]

I'm not sure what trans it is but it's definitely either a 4 speed w overdrive or a 5 speed Trans. It's a 1959 gmc 455v dump truck

[1project2many]

Most likely it's a New Process truck 5 speed . They were either direct 1:1 in 5th or OD depending on how it was built. It's a heavy, iron. This trans was used with six and eight cylinder engines so I know there is a clutch that fits it. What I can't answer for certain is if the 302 bellhousing fits the 350, although I think it might. If no one here gives a good answer then you might check at inliners.org.

[94cummins12v]

Cool cool thanks. I've tossed the idea around of throwing a 454 with an auto behind it but not sure how the auto will hold up with a 12,000lb and 8 yards of rock will hold up. Basically whatever I can find is what I'll use

[_Ogre]

it depends on what automatic you choose
most trucks come with auto trans anymore
around here that means 120,000 lbs or more

[94cummins12v]

Common sense would tell you that an auto like a 400 or 7r400 thats bolted to sbc or 454 wouldnt hold up to 120,000lbs

[mr48chev]

A Chevy V8 truck bellhousing and motor mounts should be about all you need to put a V8 big or small in that truck.

Truthfully a good 302 six might have more torque than a mild 350 though. Figure that you are going to want an rv or torque cam in the engine. With a Big block it would about match my 77 dualie with the flatbed and hoist on it.. That thing pulls about 6 mpg at best but never leaves the driveway unless it has a job to do.

[1project2many]

Yep... Auto trans in the C50 and larger trucks was an Allison for many years. The HT740



Or the DP-8962



Would hold up very well.


I've seen 5.7 light truck engine and THM425 live before in a medium duty truck. Truck had massive trans cooler and auxilliary manual tansmission to allow for starting when loaded. It was an interesting combination for certain. The 700R4 would likely go "Bye-bye" on the first drive. You could make the modern Allison work but you'd need a trans controller.

There was a discussion here just last week about bellhousings. If you can't make the 292 bell fit you could get a 505 bh from a medium duty truck and a Clark 5 speed and you should be good.

[94cummins12v]

If parts were cheaper and more available to rebuild the 302 that's in it I would in a heart beat but being you can almost throw a small block and 4 speed in there for practically nothing these days is kinda a no brainer

[OrrieG]

Originally Posted by 94cummins12v

Cool cool thanks. I've tossed the idea around of throwing a 454 with an auto behind it but not sure how the auto will hold up with a 12,000lb and 8 yards of rock will hold up. Basically whatever I can find is what I'll use

So is this going to be an every day work truck or occasional hauler? If every day work truck hauling heavy loads then I would be looking at a modern diesel auto combination, there are some build threads about the diesel. Usually the front suspension weight is an issue but probably not with the big truck. In the 70's I drove a big truck with a truck 427. We would regularly load the truck up to 60-70K. Engines lasted about 18 months. I tried to get them to convert to diesel but never did. The mechanic kept a spare long block on hand and could change it out in a day.

[1project2many]

Yeah, kinda funnny that the guy with the diesel handle wants to run a gas job...

[94cummins12v]

Use it around my 20 acres and occasionally go to the crush plant for gravel

[_Ogre]

i figured with a name like 94cummins12v you'd want an allison auto behind the bbc

[94cummins12v]

No I can't stand Allison transmissions I prefer the 5r110 and 6r140 torque shift over the Allison can handle more abuse