Real-world advice needed


Yard Art
Yard Art

Posts: 55

Joined: Sat Aug 30, 2014 9:52 pm

Location: Denton, Texas

Post Sat Nov 25, 2017 4:35 pm

Real-world advice needed

I am mechanically refurbishing a 1960 B-112, SV266, T15 4-speed trans. According to the line setting ticket and the numbers on the rear end, it has a Power Lock 3.73. My question is whether this a high enough (numerically low enough) ratio to run 60 or 65 mph without being deafened? Or do I need a ratio nearer 3? Experience tells me that calculations can get you close to an answer but real-world experience is needed too. Thanks -- Mike
    1960 B112 V8 stepside
    1966 Triumph TR4A IRS
    1993 Miata LE -- daily driver

Golden Jubilee
Golden Jubilee

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Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Sat Nov 25, 2017 5:20 pm

Re: Real-world advice needed

If your tire size is 6:50/16 the chart on the 'net suggests the tire will be about 31 inches tall. Multiply that by 3.1415 to get 97.38 inches circumference or just short of 8 feet. 8 feet will go into 5280 feet 660 times.
Now, multiply 660 by your axle ratio of 3.73 to get 2461.8 engine revolutions per mile. I you drive a mile in one minute the engine RPM should be 2461 rpm. A ratio of 3:54 will lower the engine rpm to 2336. This is about 155 rpm reduction.
I hope this is correct. CB will certainly correct me.
Last edited by nikkinutshop on Sat Nov 25, 2017 7:57 pm, edited 1 time in total.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Golden Jubilee
Golden Jubilee

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Location: Lyman, IA

Post Sat Nov 25, 2017 6:33 pm

Re: Real-world advice needed

What is the RPM (rev's per mile) of your tires? You need to know that before deciding on a gear ratio. If you plan on changing tires than do the calculation for the new tires RPM. RPM is often in the tire makers data for the tires in question.

Yard Art
Yard Art

Posts: 55

Joined: Sat Aug 30, 2014 9:52 pm

Location: Denton, Texas

Post Sat Nov 25, 2017 9:51 pm

Re: Real-world advice needed

Thanks for the replies and the effort put into them. I'm afraid I didn't phrase my question right. I need to know if it is too noisy In these pickups to run the engine at 2500 to 2800 rpm for long periods of time.
    1960 B112 V8 stepside
    1966 Triumph TR4A IRS
    1993 Miata LE -- daily driver

Golden Jubilee
Golden Jubilee

Posts: 8938

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Sat Nov 25, 2017 9:58 pm

Re: Real-world advice needed

Yes. Buy and wear ear protection or install sound insulation.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Rusty Driver
Rusty Driver

Posts: 115

Joined: Sun Dec 16, 2012 9:12 pm

Location: Western North Carolina

Post Sun Nov 26, 2017 6:10 pm

Re: Real-world advice needed

Most of the noise is from the direct drive fan.
Install a clutch fan and the noise will be much less.
Also be sure you have a fan shroud installed properly fitted.
Installing Dynamat or similar product to the firewall and cab floor & roof will also be effective.
My Junk --> 1975 IH Model 200HD, 1 ton 4x4 truck, 392, 4 speed, etc.
My cave location --> Western North Carolina

Golden Jubilee
Golden Jubilee

Posts: 1289

Joined: Sun Dec 02, 2012 7:54 am

Location: Richland, WA

Post Sun Dec 03, 2017 1:31 am

Re: Real-world advice needed

Might consider putting in an overdrive unit-
or driving at the speed the truck was designed for. Take a little more time and the back road. You might enjoy it.

(My last column in Cornbinder Connection ws about this very subject. :whistling2: )
"How the heck did that happen?"

Golden Jubilee
Golden Jubilee

Posts: 8938

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Sun Dec 03, 2017 10:59 am

Re: Real-world advice needed

Two questions come to mind. 1) on the overdrive proposal, what do you suggest for this application? 2) what do you think is the "design speed?"
I am going to try and find that Cornbinder Connection article.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Golden Jubilee
Golden Jubilee

Posts: 525

Joined: Mon Dec 17, 2012 10:50 am

Location: Fletcher, OK

Post Mon Dec 18, 2017 11:11 am

Re: Real-world advice needed

Driving at any speed in most of these pickups is loud. It is like being in a tin can being rolled down the road.
46 K3
52 L110
68 Cadillac Coupe DeVille

Golden Jubilee
Golden Jubilee

Posts: 8938

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Mon Dec 18, 2017 11:54 am

Re: Real-world advice needed

I bought a Gear Vendors overdrive for our R120 4X4. The axle ratio was 3:73. At 60 mph the Diesel engine was over 3000 rpm and too close to the governor top rpm of 4000 rpm. The interior noise was only reduced a little, but I could drive much faster. Mechanical advantage to the engine has been lost by about 23%. ( 3:73 X .78 = 2:90 )
New and better sound insulation made the biggest difference and is much less expensive than the $3000 plus for overdrive.
I installed a GVOD in ur 1940 Ford. I want 4:10 gearing in the Ford 8.8 differential to improve from a standing start acceleration. I want better gearing for the highway and a GV turns 4:10 into 3:19.
This is where an old engine may not have the torque to push your truck to the higher speed you would like.
One little thingee I should add to this speed with an OLD IHC is. high speed instability. These trucks are less aerodynamic than a Roman Brick. Around 70 MPH, I could feel the few road manners I imagined this truck to have wave goodbye and it became a theme park ride. Our R120 had a 1150 pound 6.9 Diesel for power. The extra 500 pounds of engine delayed the high speed float until about 90 mph.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive
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