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Jul 21st, 2025 | | | | Joined: Jun 2018 Posts: 32 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2018 Posts: 32 | I would like to keep the stock axle under the front of my GMC 300. I am going to install a newer axle in the rear so that I can go a little faster than 45.
I was just wondering if installing a brake booster is enough to slow this old truck down safely. Ive just heard that they dont stop very well stock and if I am going to be going 10 or 15 mph faster Id like to know if a brake booster is enough.
I have never driven the truck as of yet because its been sitting for 50 years and I am getting it prepped and running. So i have no experience as to how well they stop or dont stop.
Thanks in advance!
Logan
2010 Silverado 2500HD
1947 GMC 300
| | | | | Joined: May 2005 Posts: 8,988 Sir Searchalot | | Sir Searchalot Joined: May 2005 Posts: 8,988 | The booster has nothing to do with better stopping. Just "easier" pedal push. It was introduced for the ladies. | | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | Unless you're planning on running at full gross weight all the time (actually using it as a truck, not a Cowboy Cadillac) I think you'll be surprised at how effective the original brakes are. That's assuming you rebuild them to factory-original condition, not do a half-donkey job of it. Once they're back to good original condition, then you can decide if you need more stopping power. A vacuum booster simply makes your leg stronger- - - -it doesn't actually increase the effectiveness of the brake system or improve the traction of the tires. You'll just be able to lock up the wheels quicker with boosted brakes unless you also figure out a way to make the tires stick to the road better. A good set of radial tires might be one thing to consider before you spend a lot of time, money, and effort on a brake upgrade.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Jun 2018 Posts: 32 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2018 Posts: 32 | Alright, sounds good thank you for the info
Logan
2010 Silverado 2500HD
1947 GMC 300
| | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | Do you have 5/10 on 7.25" wheel bolt pattern? If so, '90's 3500 HD among others have D70 and 80 with that pattern, with higher ratios.
Ed
Last edited by EdPruss; 08/07/2018 2:20 AM.
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Jun 2018 Posts: 32 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2018 Posts: 32 | Im not sure of the bolt pattern i have. I think i have the motor style wheels? I think that what people have called them.
If I cant find an axle that will match up Ive got a machine shop down the road that said they could make adapters for me.
Logan
2010 Silverado 2500HD
1947 GMC 300
| | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | How many bolts are in the front and rear? Can you post a picture?
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Jun 2018 Posts: 32 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2018 Posts: 32 | Its 5 bolt front and rear.
I have been trying to figure out how to post pictures but havent quite figured it out yet.
Logan
2010 Silverado 2500HD
1947 GMC 300
| | | | | Joined: Apr 2005 Posts: 7,442 Bolter | | Bolter Joined: Apr 2005 Posts: 7,442 | Are you trying to post photos from your phone or a real computer?
Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne (Emily)
‘39 Dodge Business Coupe (Clarence)
“I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!
USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)
| | | | | Joined: Feb 2016 Posts: 1,841 'Bolter | | 'Bolter Joined: Feb 2016 Posts: 1,841 | Just yesterday I loaded 90 bales of hay on my 1957 5700, truck originally had hydro-vac booster but I have bypassed it for the time being, so with manual drum brakes on all four corners and estimated total weight of 12000 -15000 lbs. I had no problems with braking.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
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