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| | | | Joined: Oct 2009 Posts: 127 'Bolter | | 'Bolter Joined: Oct 2009 Posts: 127 | Hi All,
I am putting a 235 in my 1952 3100, and would like to get higher ratios for highway.
So I may have a chance to get the rear end from a 1954. I read that they are 3.90 gear ratio, while the 47-53 are 4.11. Is this the case? Would the difference be perceptible and worthwhile?
52 3100 project
54 3100 / 3112 ice cream truck, next project
| | | | | Joined: Oct 2010 Posts: 1,232 'Bolter | | 'Bolter Joined: Oct 2010 Posts: 1,232 | Yes - 1954 3100's had a 3.90 rear end.
Someone check my math ...
A 3.90 rear end will push your truck about 5% faster than a 4.11 at the same engine RPM.
@ 1:1 Top gear:
1 RPM at engine with a 4.11 = 1 / 4.11 RPM at wheels
1 RPM at engine with a 3.90 = 1 / 3.90 RPM at wheels
Rear wheels spin 1.0538 times faster at same engine RPM with 3.90 than with 4.11.
(4.11 / 3.90 = 1.0538)
At same engine RPM -
> 50mph with 4.11 = 52.7mph with 3.90 = (50mph X 1.0538)
> 60mph with 4.11 = 63.2mph with 3.90 = (60mph X 1.0538)
Replacing the rear end is your call.
A previous owner replaced the 3.90 in my '54 3104 with a 1950 4.11. I don't feel that I would gain enough to justify changing back to a 3.90 other knowing that I have the correct rear end. My ol' truck is no speed demon, so it's a moot point.
- Lonnie
- Lonnie My '54 3104Photos that I have shared on Stovebolt via PhotoBucket are no longer available. Please contact me if you want a photo from an old post. lonniecook [at] aol [dot] com. I sold my '54 3104 12/12/2017, but I still visit Stovebolt. OLD STUFF ... houses, furniture, cars, wine ... I love it all | | | | | Joined: Oct 2009 Posts: 127 'Bolter | | 'Bolter Joined: Oct 2009 Posts: 127 | thanks for the detailed answer. At 5% it sounds like a marginal improvement.
On the other hand the 54 rear end is a lot cheaper (i.e. free) than the Patricks gear set, and it should be a much simpler bolt-in, right? Could it be worth a try?
Last edited by wurlitzer46; 10/30/2013 5:43 PM.
52 3100 project
54 3100 / 3112 ice cream truck, next project
| | | | | Joined: Oct 2009 Posts: 127 'Bolter | | 'Bolter Joined: Oct 2009 Posts: 127 | Well, I now have that 3.90 rear end sitting in the garage - torque tube axles drums and all. Which would be the better way to go:
a) swap the 3.90 gears into the current (4.11) housing. How complicated is this?
b) swap the entire setup -- torque tube through axles to drum?
Last edited by wurlitzer46; 11/02/2013 6:38 AM.
52 3100 project
54 3100 / 3112 ice cream truck, next project
| | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | I would just put the torque tube with the 3.9 gear set, as an assembly, in your axle housing. That is unless there is something wrong with the 52 axle housing.
See the USA in your vintage Chevrolet! My Blog | | | | | Joined: Oct 2009 Posts: 127 'Bolter | | 'Bolter Joined: Oct 2009 Posts: 127 | Thanks. So, it would work to just disconnect and swap whatever unbolts from the front pumpkin cover forward?
No can of worms pressing bushings or rivets to swap gears? That sounds a lot simpler than descriptions of the Patricks conversion.
Last edited by wurlitzer46; 11/02/2013 4:47 PM.
52 3100 project
54 3100 / 3112 ice cream truck, next project
| | | | | Joined: Jan 2001 Posts: 5,337 'Bolter | | 'Bolter Joined: Jan 2001 Posts: 5,337 | If you change the torque tube as an assembly you will not need to touch the gears or adjust anything, as long as it is in good condition.
See the USA in your vintage Chevrolet! My Blog | | |
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