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Forums48
Topics116,448
Posts929,610
Members42,639
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Most Online940 Apr 5th, 2017
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1309710
Sun May 05 2019 07:57 PM
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Joined: Feb 2001
Posts: 6,609
Master Gabster
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I am not the best person to advise anyone just ask around but in my 54 1/2 ton, I have a 1979 Nova rear end with 2.73 gears and an s10 5 speed. But I live in Indiana and it is usually flat and it works for me. I have been down through the Smokeys and on the interstate, it does fine but on back roads, it takes a little shifting. Best of luck.
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1309731
Sun May 05 2019 10:14 PM
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Joined: Mar 2010
Posts: 8,601
Master Gabster
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With a 3 on the tree, I would be looking for a 3.73 out of a '67-'70 half ton truck. Its a 12 bolt rear end. You will have to weld on some spring perches. Any ratio numerically less in number (like say, a 3.55) would be a sluggish in first gear under any kind of an incline. Carl
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1309750
Sun May 05 2019 11:55 PM
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Joined: May 2006
Posts: 8,490
Master Gabster
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Another option would be to swap the transmission for an overdrive unit instead of swapping the rear axle. The SM319 was an option on these trucks from the factory, so they are a direct bolt in, even using one from a Tri-5 passenger car. I have one in mine, and 70+ is no problem for the 235.
Bill Burmeister
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1309754
Mon May 06 2019 12:09 AM
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Joined: May 2001
Posts: 1,318
Shop Shark
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When the question of top speed comes up, I always ask myself about braking.
I had a serious case of drum-brake fade in our '65 Chev on I-80 in Wyoming one time (~1969) when a big buck deer, trying to block most of the 2 lanes, stared me down. I couldn't stop but thankfully I could steer a bit. Drifted right by him.
45 MPH is great for me.
1948 3/4-Ton 5-Window Flatbed Chevrolet 27 Years of Daily Driving. Now with a '61 261, 848 head, Rochester Monojet carb, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.
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Re: Woah! She’s slow.
[Re: LONGBOX55]
#1309759
Mon May 06 2019 01:21 AM
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Joined: Sep 2009
Posts: 107
OP
Shop Shark
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I’m not familiar with the sm 319. Does it shift the same as a 3 speed? How do you shift it to overdrive? Do you know if a driveshaft mod is required? Thank you for the help!
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1309766
Mon May 06 2019 01:42 AM
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Joined: Feb 2003
Posts: 1,315
Shop Shark
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I thought the same on my first drive in my 37,that problem has been solved with a T-5 and 3.55 gears.
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1309770
Mon May 06 2019 02:00 AM
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Joined: May 2006
Posts: 8,490
Master Gabster
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The SM 319 is a variant of the SM 318 3 speed that is standard in the '55-'66 trucks. Both transmissions also saw use in GM passenger cars in the same time period. The SM 319 is setup with a Borg-Warner overdrive unit in place of the tailshaft and its housing. The main part of the transmission is the same as the standard 3 speed, so the shifter hookup and operation is identical. The overdrive is, if installed as the factory did it, shifted electrically via a solenoid on the housing. The shifting is done automatically by lifting off the throttle at approximately 28 mph (that speed can vary depending on rear ratio and tire size), which is when the contacts in the governor close. Overdrive can be used in any forward gear. There is also a manual lockout cable which locks the overdrive, making the transmission operate as a normal 3 speed. If you use a transmission from a '55/56/57 Chevrolet Passenger car or '55-'59 Truck, no driveshaft mods will be required. The only change, depending on what the trans came from, would be to swap the shift cover out as Passenger and '55 6 cylinder Truck versions are different from '55-'59 Truck. Here's the shop manual section from the '55 manual can explain things a little better on operation http://chevy.oldcarmanualproject.com/shop/1955truck2/55ctsm0715.htmI've had one in mine for the last 20 years, it's probably the best thing I did to it.
Bill Burmeister
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1309787
Mon May 06 2019 04:22 AM
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Joined: Feb 2001
Posts: 1,046
Shop Shark
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40 - 45 mph in my truck with standard (1956) 3.9 rear is about 1800 rpm . A standard 235 1/2 ton should cruise easy at 60mph , it will go faster , but your mileage will go away  If you have too much noise , determine where it is coming from and fix that . I predict it may be a cheaper option . Jerrys "pull the fan off" is a good way to isolate noise issues. Consider taller tyres as a small gearing adjustment . I agree with the brake comments .
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1309813
Mon May 06 2019 03:14 PM
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Joined: Sep 2009
Posts: 107
OP
Shop Shark
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Great info guys I really appreciate it. Love the idea of the sm319. I’ll look into finding one. I did the brakes with a hidden booster and discs on the front so she stops great. Not that I want to go that fast, I just want to go with the flow of traffic.
Last edited by Skidmarks; Mon May 06 2019 03:15 PM.
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Re: Woah! She’s slow.
[Re: Skidmarks]
#1310130
Thu May 09 2019 02:44 PM
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Joined: Jan 2002
Posts: 1,975
Shop Shark
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Took my truck out for a spin yesterday. With 3.55 gears in back behind a SM420, my RPM's are 2200 at 55 MPH, 2600 at 60 MPH.
Craig's '50 Chevy 3100 5 window My truck If I'm not working on my truck or VW camper, I'm fishing with the wife or smoking Salmon.
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