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| | | | Joined: Mar 2009 Posts: 124 'Bolter | | 'Bolter Joined: Mar 2009 Posts: 124 | i searched through the archives but i am still confused.
i have a '54 3/4 ton with the open driveline and an sm420. is there an overdrive available for my set-up? preferably something that can be found in a junkyard. | | | | | Joined: Oct 2003 Posts: 5,152 Cruising in the Passing Lane | | Cruising in the Passing Lane Joined: Oct 2003 Posts: 5,152 | Anything that has ever been installed might be found in a junk yard. GM did not make an overdrive for the SM420.
The two options that come to mind are the Ranger and the Gear Vendors. The Ranger goes in front of the transmission and the Gear Vendors goes behind.
The Ranger is much less expensive than the Gear Vendors though neither is cheap. I think you'd be more likely to find either used on craigslist than in a junk yard.
Other options to consider are changing the rear axle to one that is available with more highway speed friendly gears or swapping to a transmission with an overdrive.
1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble... | | | | | Joined: Mar 2009 Posts: 124 'Bolter | | 'Bolter Joined: Mar 2009 Posts: 124 | ok. so borg and warner did not make an od unit for the sm420?
i have read about the gear vender and ranger units. i did not want to spend the big $ on those.
i guess i'll need to concider the dif or trany swap if i decide i need the extra mph.
thank you. | | | | | Joined: Oct 2003 Posts: 5,152 Cruising in the Passing Lane | | Cruising in the Passing Lane Joined: Oct 2003 Posts: 5,152 | As far as I know there is no Borg Warner OD for the SM420. I could be wrong and it wouldn't be the first time.
You can convert to something like a T-5 which will give you the overdrive, but is not a heavy duty transmission. You might find one of those for a couple hundred.
Aside from that most the transmission options are quite a bit more expensive unless you find a deal somewhere.
The 4.10 gears for the stock axle are hard to find. It may take months to find a set used.
A complete rear axle replacement might be the cheapest option. I've seen appropriate axles change hands pretty cheap. I have a Dana 70HD I was given and a GM 14-bolt that came with a $100 truck. You'll still spend money on new u-bolts and brakes, but it may not be much.
Good luck!
1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble... | | | | | Joined: Jan 2008 Posts: 4,961 'Bolter | | 'Bolter Joined: Jan 2008 Posts: 4,961 | I agree that the cheapest way to go faster is get a later complete rear. 4.10 was standard for many years. I think since 07 GM offered a 3.73 in 3/4 ton. I have a 3.73 in my 09. Late model rears are not that expensive because there isn't much demand for them. They hardly ever break. | | | | | Joined: Mar 2009 Posts: 124 'Bolter | | 'Bolter Joined: Mar 2009 Posts: 124 | thanks for the advise. i'll keep all that in mind. | | |
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