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  #1  
Old July 28th, 2021, 04:42 PM
ZDADDY ZDADDY is offline
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Default 1960 Gmc 305 v6

Picked up this beauty a few weeks ago, started to tear into her, found this site, and I'm getting excited about this Truck and this engine! I need some feedback from you gearheads on going forward. My plan is to drive this Truck.I want it to drive 70mph on the interstate with no problems, without rpms redlining. I am pulling engine, and taking to machine shop for complete overhaul. Need advise.......I'm not big on loud *** trucks that can do burn outs. Would like my daughter to learn how to drive a stick in this truck.It was a 3 on the tree, but somebody changed it to floor shift before I got it.Questions..........

Do they make different gears for rear end? Or do I have to replace rear end with something more newer? Its the granny tranny.

Disc brakes?

Suspension?

Holly carb rebuild?

Any comments would be great Thanks

Zdaddy



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  #2  
Old July 29th, 2021, 06:58 AM
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Ed Snyder Ed Snyder is offline
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Default Re: 1960 Gmc 305 v6

Quote:
Originally Posted by ZDADDY View Post
Picked up this beauty a few weeks ago, started to tear into her, found this site, and I'm getting excited about this Truck and this engine! I need some feedback from you gearheads on going forward. My plan is to drive this Truck.I want it to drive 70mph on the interstate with no problems, without rpms redlining. I am pulling engine, and taking to machine shop for complete overhaul. Need advise.......I'm not big on loud *** trucks that can do burn outs. Would like my daughter to learn how to drive a stick in this truck.It was a 3 on the tree, but somebody changed it to floor shift before I got it.Questions..........

Do they make different gears for rear end? Or do I have to replace rear end with something more newer? Its the granny tranny.

Disc brakes?

Suspension?

Holly carb rebuild?

Any comments would be great Thanks

Zdaddy



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Welcome to the forum, Zdaddy! We may be a little slow answering all your questions, but don't give up. I'm sure most of your questions will get answered eventually.

You don't say whether your truck is half or three-quarter ton. The half ton rear ends lend themselves to taller highway gears of course. Stock half ton ratios were 3.07, 3.54, and 3.92. Quickest way to find out what you've got is to roll it slowly forward for one revolution of the rear wheels while having a second person count the number of times the driveshaft goes around.

If you've got a three quarter ton, most likely it's got a 4.10 or 4.56. If I remember right, the tallest ratio you can fit is a 3.73. That's what I did to a truck I bought several years ago that came with a 4.56 rear end -- changed to a 3.73. With 32" tall tires, freeway cruising was no problem.

Looks like you're off to a good start! Keep us informed of your progress.
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1962 K1000 Suburban 401M & SM420
1965 2500 Suburban 351C & SM420 with Watson overdrive
1967 CM1500 pickup 351E & NP435
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  #3  
Old July 29th, 2021, 12:56 PM
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Default Re: 1960 Gmc 305 v6

Welcome to the Wonderful World of V-6's PLEASE CHECK AND ENJOY THIS LINK, it has every single thing you'll ever want oe need to know about our trucks. It was created by Jolly Goodfellow.

http://6066gmcguy.com/


I have a 1/2 ton GMC V-6 with a factory rear differential DANA 44 and that originally had a stock 3.92 ring and pinion. I swapped it down to a 3.23 from Precision Gear, that helped a lot but I had no overdrive, so I stayed on the low roads.....

I recently swapped out my worn out 4 Speed hydramatic to a 700R4 - if you consider that you'll need the factory or aftermarket trans adaptor to mate up an automatic. Once I made the swap and the truck had OD, I can cruise at 70+ and only turn 1500-1900. I tested at 80 mph and was only turning 1750-1800. See screen shot

Finding parts will sometimes be a quest but they are out there, reach out to both Kanter and EGGE Auto.
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  #4  
Old July 29th, 2021, 05:51 PM
Jim A Jim A is offline
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Default Re: 1960 Gmc 305 v6

I have owned and appreciated a 1960 3/4T, 4 spd GMC 305 for over 50 years.
It has literally done every thing I have asked of it and done them well.
I never have asked it to cruise on the interstate at 70 MPH, however, and never would.
Your new truck has great potential for many years of satisfaction and reliable service, but it was not designed or built for speed.
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  #5  
Old July 29th, 2021, 07:46 PM
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Default Re: 1960 Gmc 305 v6

It is a VERY LOW RPM motor. Built for torque. To buy one you must realize that. If you want a hiway truck, there are many choices. Many are very expensive. I don't know how much you can do. I don't know your skills, tools, experience. The suggestion are coming in from members. It all takes work and some time. Maybe just a rear diff gear change will work. It worked for ED. That would be your first step. If you are going to take it to have it done, it will be way cheaper to find a 12 bolt Chevy donor to swap in. The only way to be sure of any ratio is to take off the cover and read the numbers on the ring gear. Please state if it is a 1/2T or 3/4T.
My 1960 GMC 1/2T had a Dana 44, Jakes 1960 GMC 1/2T has a Dana 44. Yours does not. Don't know what it is yet, corporate 10 bolt? or a drop out? or other. 1/2 T or 3/4 T? Could be stock or could have been swapped already. I can't see your lug nuts to tell if yours is 1/2T or 3/4T.
Your truck seems to have some custom cab features.

Last edited by AZKen; July 29th, 2021 at 08:21 PM.
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  #6  
Old July 29th, 2021, 10:59 PM
ZDADDY ZDADDY is offline
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Default Re: 1960 Gmc 305 v6

Quote:
Originally Posted by Ed Snyder View Post
Welcome to the forum, Zdaddy! We may be a little slow answering all your questions, but don't give up. I'm sure most of your questions will get answered eventually.



You don't say whether your truck is half or three-quarter ton. The half ton rear ends lend themselves to taller highway gears of course. Stock half ton ratios were 3.07, 3.54, and 3.92. Quickest way to find out what you've got is to roll it slowly forward for one revolution of the rear wheels while having a second person count the number of times the driveshaft goes around.



If you've got a three quarter ton, most likely it's got a 4.10 or 4.56. If I remember right, the tallest ratio you can fit is a 3.73. That's what I did to a truck I bought several years ago that came with a 4.56 rear end -- changed to a 3.73. With 32" tall tires, freeway cruising was no problem.



Looks like you're off to a good start! Keep us informed of your progress.
Hey Ed!!!! Thanks for the reply......I think my truck is a halfton it has 6 lugs. Pulling engine tomorrow.I am going to take pumpkin off and see what I got. I posted a pic under rear end disscussion and havnt figured out what I have yet.Someone posted a chart with diffrent rear end pics, but mine does not look like any of them. I really appreciate the feedback.I may take the advise of everyone here going forward on what to do, since most have done it before.

Zdaddy

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  #7  
Old July 29th, 2021, 11:05 PM
ZDADDY ZDADDY is offline
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Default Re: 1960 Gmc 305 v6

Quote:
Originally Posted by jbgroby View Post
Welcome to the Wonderful World of V-6's PLEASE CHECK AND ENJOY THIS LINK, it has every single thing you'll ever want oe need to know about our trucks. It was created by Jolly Goodfellow.

http://6066gmcguy.com/


I have a 1/2 ton GMC V-6 with a factory rear differential DANA 44 and that originally had a stock 3.92 ring and pinion. I swapped it down to a 3.23 from Precision Gear, that helped a lot but I had no overdrive, so I stayed on the low roads.....

I recently swapped out my worn out 4 Speed hydramatic to a 700R4 - if you consider that you'll need the factory or aftermarket trans adaptor to mate up an automatic. Once I made the swap and the truck had OD, I can cruise at 70+ and only turn 1500-1900. I tested at 80 mph and was only turning 1750-1800. See screen shot

Finding parts will sometimes be a quest but they are out there, reach out to both Kanter and EGGE Auto.
Jbgroby,

That's exactly what I want!!!!!! Low rpms going 70/80...........How does that work with a manual 4speed? I would like to keep the floor shifter......is that doable or to much a pain in the ***?
Got any more pics? I need inspiration. Do you have to change tranny and rear end? What trannies bolt up to the v6?

Thanks for the reply
Zdaddy

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  #8  
Old July 29th, 2021, 11:12 PM
ZDADDY ZDADDY is offline
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Default Re: 1960 Gmc 305 v6

Quote:
Originally Posted by Jim A View Post
I have owned and appreciated a 1960 3/4T, 4 spd GMC 305 for over 50 years.

It has literally done every thing I have asked of it and done them well.

I never have asked it to cruise on the interstate at 70 MPH, however, and never would.

Your new truck has great potential for many years of satisfaction and reliable service, but it was not designed or built for speed.
Jim,

Thank you for the response. Your right, they were made to work. And now that she is retired, its time to do some modern upgrades so she can still show everyone she's still got it going on. I know I'm treading a fine line with keeping these pieces of American history intact, but a part of me really wants to drive this truck around, I live off an interstate, and it must be able to drive on it. That's all I want no more no less. Hopefully with this forums guidance, I can make that happen. Thanks you again for the comment.

Zdaddy

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  #9  
Old July 29th, 2021, 11:31 PM
ZDADDY ZDADDY is offline
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Default Re: 1960 Gmc 305 v6

Quote:
Originally Posted by AZKen View Post
It is a VERY LOW RPM motor. Built for torque. To buy one you must realize that. If you want a hiway truck, there are many choices. Many are very expensive. I don't know how much you can do. I don't know your skills, tools, experience. The suggestion are coming in from members. It all takes work and some time. Maybe just a rear diff gear change will work. It worked for ED. That would be your first step. If you are going to take it to have it done, it will be way cheaper to find a 12 bolt Chevy donor to swap in. The only way to be sure of any ratio is to take off the cover and read the numbers on the ring gear. Please state if it is a 1/2T or 3/4T.
My 1960 GMC 1/2T had a Dana 44, Jakes 1960 GMC 1/2T has a Dana 44. Yours does not. Don't know what it is yet, corporate 10 bolt? or a drop out? or other. 1/2 T or 3/4 T? Could be stock or could have been swapped already. I can't see your lug nuts to tell if yours is 1/2T or 3/4T.
Your truck seems to have some custom cab features.
AZken,

Thanks for the response, I traded a 54 Pontiac for this truck that ran and drove, for a 1960 gmc 1/2 ton, 6 lug, big block v6......that doesn't run.........That's about all I know about it.......That's why I'm here, for guidance from people like you, who have one, or have had several.I am going to post pics of the rebuild as I go, I got the money, and the time, just need the dos and donts from people who done it before. I live off an interstate, and would like to have it drive down it. With low rpms. I rebuilt a 63 falcon in my 20s, (strait 6) and it always had high rpms when driving it, and don't want to reapeat that.
Iv never replaced gears in a rear end, but that don't mean I can't do it.I can take apart **** and put it back together, but that don't make me an expert. The truck had a column shift In it, but currently has a 4 speed floor shifter in it. If I would have noticed that when I traded for it, I probably wouldn't have bought it.I'm pulling engine tommorro, and off to the machine shop.Already have new gas tank, and will do brakes and brake lines while being bored and honed.Any advice would be appreciated.

Thanks for the comment.

Zdaddy

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  #10  
Old July 30th, 2021, 12:37 AM
Ed Snyder's Avatar
Ed Snyder Ed Snyder is offline
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Default Re: 1960 Gmc 305 v6

Quote:
Originally Posted by ZDADDY View Post
Hey Ed!!!! Thanks for the reply......I think my truck is a halfton it has 6 lugs. Pulling engine tomorrow.I am going to take pumpkin off and see what I got. I posted a pic under rear end disscussion and havnt figured out what I have yet.Someone posted a chart with diffrent rear end pics, but mine does not look like any of them. I really appreciate the feedback.I may take the advise of everyone here going forward on what to do, since most have done it before.

Zdaddy

Sent from my P027 using Tapatalk
With six lugs, yours is definitely a half ton model. I'm guessing your rear end is not original to the truck though. You might be able to figure out what you've got by looking at this page --- https://m.roadkillcustoms.com/differ...ication-chart/ For the best highway cruising, you probably want a ratio somewhere between 3.00 and about 3.50. If you need to change your rear gears, I highly recommend getting a professional shop to do it for you. Changing the rear gears is a simpler, less expensive project than changing to an overdrive transmission. Tall rear tires will help with highway cruising too.
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1962 K1000 Suburban 401M & SM420
1965 2500 Suburban 351C & SM420 with Watson overdrive
1967 CM1500 pickup 351E & NP435
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