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#24500 09/29/2003 3:12 PM | Joined: Sep 2003 Posts: 72 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2003 Posts: 72 | Hi Guys,
Been looking for a good site to gather info on my old 49 GMC 1/2 ton. Found it. This site is great. Here's my question. I have a 49 GMC 1/2 ton and a 77 GMC 1/2 ton. I am pondering the idea of putting the running gear (305, tranny, driveshaft and rear end) from my 77 into my 49 to have a better driving highway truck. Any info or suggestions to my ideas would be greatly appreciated. Thanks to everyone in advance.
kskt4 | | |
#24501 09/29/2003 3:54 PM | Joined: May 2003 Posts: 328 Shop Shark | | Shop Shark Joined: May 2003 Posts: 328 | This swap will work, but you will need motor mounts and a trasmission mount. As far as the drive shaft is concerned, you will have to put the rear end and transmission in place and measure to see if it will work. You can even bolt your front suspension off of the 77 truck on to the frame of your 49 to upgrade to independent front suspension and disc brakes. I plan on doing this myself. Hopefully others will drop in and give us the ins and outs of doing this.
Phil
Never hold your farts in. They travel up your spine and into your brain...that is where crappy ideas come from.
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#24502 09/29/2003 4:59 PM | Joined: Apr 2002 Posts: 2,168 A teacher, but always an apprentice. | | A teacher, but always an apprentice. Joined: Apr 2002 Posts: 2,168 | ksk you will need motor mounts and a tranny mount, those should go in with a little work. lots of room under the hood. the drive shaft(i assume your 77 is a long box) might need to be shortened. that's easily done by a qualified shop. I don't know about a shortbox driveshaft. what are you building, mostly stock, with updated drivetrain? Or a rod. I have a 50, and I was going to use a rear out of a 83, but it was a little too wide for the tires i wanted to use. with the 77 rear, you will probably only be able to stuff 8 inch wide tires under the fenders, and heck those might be sticking out just a bit. A better option, is a rear out of a 70's camaro, firebird, nova, etc. These are narrower than the truck rear, allowing for more tire options. I pulled my rear out of a 79 Firebird. Looks nice with 8 inch tires on all 4 corners. Do a search on this site, i guarantee you'll find lots on this subject. Hopes this helps.  | | |
#24503 09/30/2003 3:20 AM | Joined: Sep 2003 Posts: 72 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2003 Posts: 72 | Thanks Guys,
I will look into the info you gave me. Should be fun. I'll let you know how it goes.
kskt4 | | |
#24504 09/30/2003 5:51 PM | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | The 77 rearend may be a bit wide. The 72-up are a few inches wider than the 60-71's. I have a '67 6- lug 3.07 rearend going into my '50.
Paint & Body Shop moderator
A lone amateur built the Ark. A large group of professionals built the Titanic. | | |
#24505 10/02/2003 11:35 PM | Joined: Sep 2003 Posts: 72 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2003 Posts: 72 | 4ontheFloor,
I believe I measured backing plate to backing plate on both my 49 and 77. They were within a half an inch if I'm not mistaken. I will measure tonight when I get home from work to confirm and get back to you.
kskt4 | | |
#24506 10/03/2003 5:34 AM | Joined: Sep 2003 Posts: 72 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2003 Posts: 72 | 4ontheFloor,
Measured the distance from backing plate to backing plate. The 77 is 57" and the 49 is 55 5/8". It's more than I thought. Is that to much?
kskt4 | | |
#24507 10/03/2003 10:33 AM | Joined: Feb 2001 Posts: 1,897 Member | | Member Joined: Feb 2001 Posts: 1,897 | You will want to measure from the spot where the wheel mounts to the other side where the wheel mounts.
the reason to measure these points is that the brake drums may be wider, putting the wheel mount area out further.
Check to be sure.
There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!
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#24508 10/03/2003 3:21 PM | Joined: Sep 2003 Posts: 72 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2003 Posts: 72 | Mechainiac,
Thanks. I will measure that today and get back to you.
kskt4 | | |
#24509 10/05/2003 10:54 PM | Joined: Sep 2003 Posts: 72 Wrench Fetcher | | Wrench Fetcher Joined: Sep 2003 Posts: 72 | Mechainiac,
Well I did some measuring and removed a few rear end covers and here's what I found out. The distance from where I will mount my wheels on the 77 is 63 1/4". The distance on my 49 is 61 5/8". These aren't exact measurements but they are within 1/4". So with the extra width on the 77 rear end is that going to cause me any trouble with my tires? Next thing is I counted the teeth on my 49 rear end. 36 on the crown and 8 on the pinion. So that gives me a 4.5/1 gear ratio. Is that correct? Not exactly what you want for highway gears. I then counted the teeth on the 77. I coudn't rotate the axle cause I couldn't find the keys but I got 36 teeth on the crown and I think 11 or 12 on the pinion. So that would give me either 3.27/1 or 3/1 gears. Much better for the highway driving. So with this given data can I use the rear from my 77 in my 49?
kskt4 | | |
#24510 10/06/2003 8:54 AM | Joined: Oct 2001 Posts: 3,458 Extreme Gabster | | Extreme Gabster Joined: Oct 2001 Posts: 3,458 | You should be able to use it but you will want to check to make sure the tires won't rub on the inside of the fenders. Pop the old axle off, set the new axle in there, put wheels and tires on it, and lower the frame until the bump stops hit the axle and there you go. I bet it will rub, but if you found wheels with a deeper offset you would be fine. It's only about 3/4" per side. You could also adjust the fenders if you feel like it.
Paint & Body Shop moderator
A lone amateur built the Ark. A large group of professionals built the Titanic. | | |
#24511 10/06/2003 12:08 PM | Joined: Jan 2000 Posts: 1,586 Extreme Gabster | | Extreme Gabster Joined: Jan 2000 Posts: 1,586 | kskt4 ,I put an 80 Chevy 1/2 ton 4x4 rear axle(6 lug)in a 51, it's not too wide even with 225/70 tires on 15x7 rims, plenty of fender clearance.I'm thinking here the 4x4 axle is the same width as the two wheel drive version? | | |
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