Two speed rear end in a P/U?! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Farm_Truck · 08-03-2018, 10:17 PM

Alrighty folks. new to the website and new to the trucks older than '72. (Save for a '55 3100 but that's besides the point.) Anyway. Looking at picking up a '63 C20 with a 4 speed and the 2(71?) small block. It's cheap, and halfway buried in the ground, but mark my words I'm gonna try and get it roadworthy. I know it's probably the least of my worries, but I was wondering if it was possible to stick a two speed rear end from a '58 dump truck under the pickup. It's only got a 4 speed, but it would be the only one around. If it is possible, how hard is it to hook up? Does it need vacuum or positive air pressure? Do I need to change the driveshaft or frame? And, is it possible to change the hubs on them, or would I have to stick with the huge effin tires and rims? Or, would there be a better option for it? Thanks for the help- in advance of course.

**Captainfab** · 08-03-2018, 11:48 PM

The medium duty truck differentials are much larger physically than a Eaton HO52/72. Plus the high gear in those 2 speed differentials are a much lower gear than what is in the HO52/72. They do need vacuum to shift and yes you will be stuck with using the original hubs and 20" wheels. I see really no point is making this swap. If you want a higher gear in the C20, either change the trans to a OD trans, or change the differential to a 14 bolt or Dana 60 with higher gears.

**paulspickupparts** · 08-04-2018, 09:58 PM

X2^

Farm_Truck · 08-05-2018, 01:32 AM

Quote:

Originally Posted by Captainfab

The medium duty truck differentials are much larger physically than a Eaton HO52/72. Plus the high gear in those 2 speed differentials are a much lower gear than what is in the HO52/72. They do need vacuum to shift and yes you will be stuck with using the original hubs and 20" wheels. I see really no point is making this swap. If you want a higher gear in the C20, either change the trans to a OD trans, or change the differential to a 14 bolt or Dana 60 with higher gears.

Got any clue what would be the best OD tranny to throw in behind it? The engine is stuck, so I might just tear it out and drop the cheapest SBC I can find into it.

vince1 · 08-05-2018, 10:25 AM

The 700R4 is popular, the latest version that still has the cable is probably the best. You would also need to do a cross member modification. Finding a 350 from an old P/U (year? ) with tranny attached would be a good score.

**Captainfab** · 08-05-2018, 11:23 PM

If you want to stay with a manual trans and use your C20 as a truck, a NV4500 would be the best choice IMO. If you want to go with an auto trans a 700R4 will work in a C20 if it is built right. If this is mainly a cruiser, then a NV3500 or a T5 will work for a manual trans. And again if a auto trans is desired a 700R4. The 4L80E is much heavier duty trans, basically a TH400 with OD, but they can be $$$ to retrofit. From a budget perspective, changing the differential will be much cheaper.

Quote:

Originally Posted by Farm_Truck

Got any clue what would be the best OD tranny to throw in behind it? The engine is stuck, so I might just tear it out and drop the cheapest SBC I can find into it.

Farm_Truck · 08-07-2018, 09:15 PM

Quote:

Originally Posted by vince1

The 700R4 is popular, the latest version that still has the cable is probably the best. You would also need to do a cross member modification. Finding a 350 from an old P/U (year? ) with tranny attached would be a good score.

Not really looking for an auto.

Quote:

If you want to stay with a manual trans and use your C20 as a truck, a NV4500 would be the best choice IMO. If you want to go with an auto trans a 700R4 will work in a C20 if it is built right. If this is mainly a cruiser, then a NV3500 or a T5 will work for a manual trans. And again if a auto trans is desired a 700R4. The 4L80E is much heavier duty trans, basically a TH400 with OD, but they can be $$$ to retrofit. From a budget perspective, changing the differential will be much cheaper.

As much of a sin as it is, I'd devote it to more of a fixer/beater truck. The kind that you don't worry about dings and scratches, yet at the same time put rocker panels in. Kind of a conflict of interest, but whatever.

TJ's Chevy · 08-08-2018, 12:59 AM

Put a road ranger gear splitter between the engine and trans.

**The Rocknrod** · 08-08-2018, 09:50 AM

Or you could go with a Gear Vendors Overdrive - http://www.gearvendors.com/cg2wd3s.html

08-03-2018, 10:17 PM	#1
Farm_Truck Registered User Join Date: Aug 2018 Location: Algona, Iowa Posts: 3	Two speed rear end in a P/U?! Alrighty folks. new to the website and new to the trucks older than '72. (Save for a '55 3100 but that's besides the point.) Anyway. Looking at picking up a '63 C20 with a 4 speed and the 2(71?) small block. It's cheap, and halfway buried in the ground, but mark my words I'm gonna try and get it roadworthy. I know it's probably the least of my worries, but I was wondering if it was possible to stick a two speed rear end from a '58 dump truck under the pickup. It's only got a 4 speed, but it would be the only one around. If it is possible, how hard is it to hook up? Does it need vacuum or positive air pressure? Do I need to change the driveshaft or frame? And, is it possible to change the hubs on them, or would I have to stick with the huge effin tires and rims? Or, would there be a better option for it? Thanks for the help- in advance of course. __________________ Chronically broke thanks to my '84 Scottsdale K20

08-03-2018, 11:48 PM	#2
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,252	Re: Two speed rear end in a P/U?! The medium duty truck differentials are much larger physically than a Eaton HO52/72. Plus the high gear in those 2 speed differentials are a much lower gear than what is in the HO52/72. They do need vacuum to shift and yes you will be stuck with using the original hubs and 20" wheels. I see really no point is making this swap. If you want a higher gear in the C20, either change the trans to a OD trans, or change the differential to a 14 bolt or Dana 60 with higher gears. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

08-04-2018, 09:58 PM	#3
paulspickupparts Senior Member Join Date: Sep 2011 Location: Seward Nebraska Posts: 1,596	Re: Two speed rear end in a P/U?! X2^

08-05-2018, 10:25 AM	#5
vince1 Registered User Join Date: Jan 2013 Location: Calgary Alberta Posts: 1,170	Re: Two speed rear end in a P/U?! The 700R4 is popular, the latest version that still has the cable is probably the best. You would also need to do a cross member modification. Finding a 350 from an old P/U (year? ) with tranny attached would be a good score.

08-08-2018, 12:59 AM	#8
TJ's Chevy Registered User Join Date: Mar 2013 Location: Southern Oregon Posts: 10,384	Re: Two speed rear end in a P/U?! Put a road ranger gear splitter between the engine and trans. __________________ 1966 Chevy C10 "Project Two Tone" http://67-72chevytrucks.com/vboard/s...d.php?t=596643 1964 GMC "Crustine" semi-build:http://67-72chevytrucks.com/vboard/s...d.php?t=665056 My youtube channel. Username "Military Chevy": https://www.youtube.com/channel/UC_h...fzpcUXyK_5-uiw

08-08-2018, 09:50 AM	#9
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Two speed rear end in a P/U?! Or you could go with a Gear Vendors Overdrive - http://www.gearvendors.com/cg2wd3s.html __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?



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