Looking for advice/opinions on whether 3.55's would work well with a 235 with a T5 (.72 overdrive) or if it would be too much gear? Looking to be able to cruise at 60 mph +/- at a decent RPM.
I cruise all day long at 60mph with a 216, 3spd, 4.11:1 rear end with a torque tube.
One of the keys to that is not to put dinky small diameter tires on the truck. I put original style 16" rims with large diameter tires ~30" . 225/85-R16 is the closest modern size to original bias ply.
Last edited by Otto Skorzeny; 10/30/202411:57 PM.
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I cruise all day long at 60mph with a 216, 3spd, 4.11:1 rear end with a torque tube.
One of the keys to that is not to put dinky small diameter tires on the truck. I put original style 16" rims with large diameter tires ~30" . 225/85-R16 is the closest modern size to original bias ply.
My wheels are the original 17" artillery wheels. 29" diameter according to Coker, so not small. So it sound like with overdrive I wouldn't need more gear.
"Final drive should be between 3.0 and 2.50. If overdrive is .73 and your axle is 3.73, your final drive will be 3.73 X .73 = 2.72 (perfect!)!"
So your 3.55 x .72 overdrive =2.59 (so your in the ballpark)
Excellent. Thanks!
For anyone else who may also be interested, according to Tom's article, the range of gears for my T5 to be ideal in both first gear and overdrive (3.76 and .72) would be 3.90's to 3.55's. 3.90's being as low as you'd probably want to go for a good 1st gear, and 3.55's as tall as you'd want to go for a usable overdrive.
You can use either a fast rear or an over drive, but not both. With a 3.55 overdrive would be worthless. Even a larger engine would struggle. 3.55 is all your 235 can handle. Or a 3.90 or 4.11 with overdrive.
Which 3.55 rear are you looking at? Or was that just a number for discussion purposes?
I have a separate thread where I was asking about swapping a '57 center section into my '36 housing. Turns out that's not possible, but before I knew that, I found a '57 center section with 3.55 gears for sale, as well as one with 3.90's. That's why I was asking for opinions on ratios.
I also have a Ford 9" rear here and a 3.50 center section that I could use. I had that rear end for a different project that was never used. It's a posi and 31 spline. A bit overkill for the 235, plus I'd have to buy new 6 lug axles to use it, so I'm looking into other options instead.
It all depends on the gear ratios in your T5, RB. Let me please give you an example: I have a 1959 235, a T5 and a GM 12 bolt rear end with a 3.07 ratio. It works fine. Here's why...the OEM 3 speed in the 1/2 ton truck had a 2.94 first gear and a 4.11 rear end which gave it a 12.08 final gear ratio. I have a 4.03 first and a 3.07 rear end so as you can see my final gear ratio in first is about the same as the OEM. On through the gears (the first 3 of which feel just like the OEM pickup gears) we go and in fifth my T5 ratio is .86 and so with my 3.07 rear end my overall ratio is 2.64. Now one thing I think is good to keep in mind is that if you had bought an El Camino or a station wagon with a 235 and a 3 speed with overdrive you would have had a 3.90 rear end and in overdrive the reduction would have been 30% making your final ratio 2.73. Awfully close to the same ratio I have. In a notably hilly or windy area I'll drop back to 4th and my overall will be 3.07 (since 4th gear is 1.00). Otherwise I'll zip along in 5th and at 60mph I'll be around 2000 rpm. Maximum torque for my engine occurs at 2000 rpm, by the way. Hope that helps.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
Instead of chasing that elusive "sweet spot" in the performance envelope with all sorts of creative gear changes, why not just build some more torque into the engine, and/or flatten the torque curve where a few RPM's difference doesn't really matter? The old NASCAR adage applies here- - - -"Horsepower is to brag about- - - -torque wins races!" 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!
Instead of chasing that elusive "sweet spot" in the performance envelope with all sorts of creative gear changes, why not just build some more torque into the engine, and/or flatten the torque curve where a few RPM's difference doesn't really matter? The old NASCAR adage applies here- - - -"Horsepower is to brag about- - - -torque wins races!" Jerry
Jerry, I'm not really chasing a sweet spot, and not looking at creative gear changes. I'm just trying to figure out ahead of time a range of gear ratios that would work ahead of my search for an open drive rear end for the truck. I asked about 3.55 specifically only because I found a center section in that ratio. (and it turns out I can't use it anyway as per our discussion in the other thread)
That being said, I'm all for building more torque, but I'm not looking to spend an arm and a leg doing so. I just want to cruise around in my truck!
I think all the members try to help in their own way so take it all in and make your own informed decision. Jerry's comment about needing torque has merit. The old truck has the aerodynamics of a billboard travelling down a highway. At highway speeds (60-65 mph) a 235 with a 3-speed overdrive (4.11 X 0.70 = 2.87 final gear equivalent) can/may use up more gasoline than a 261 with the same transmission at the same speed.
Mr. Google tells me that to "cruise around" means to move or travel slowly around an area, usually without a specific purpose but with the hope of finding something interesting. A lot of people do this quite easily in a stock truck.
Factor in that old, well-used rear axles tend to have worn ring and pinion gears, bearings and seals. This can become a big $$ headache. Since you are going the T5 route you may want to ponder the 4X4 S10 Blazer rear axle.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
Just FYI, RB...In 1959 GM started working to lower smog and increase efficiency. From actual GM correspondence, "Also new is a special economy package consisting of a small throat carburetor and lower ratio rear axle, which further improves the economy of the Thriftmaster on Series 31 and 32 models. All engines continued from the previous year feature improved efficiency, greater durability and more favorable performance characteristics. Major refinements include a lower lift camshaft and modified lubrication system on the Thriftmaster engines. Gray paint is again used on the 235, light duty 283 and 348 and green paint on the 261 and heavy duty 283 units."
The bottom line is the 235 enjoyed a nice torque line which saw near maximum torque around 1600 rpm stretching all the way over to 2800 rpm. So, one way to get more usable torque in a long flat range (without spending an arm and leg) is to use a 1959 camshaft...or one that mimics it. Good luck!
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
The Melling CCS-1 solid lifter cam is available again- - - -a bit scarce, yes, but not "unobtanium" like the Elgin E-293S that is a clone of the 261/Corvette cam in every dimension except the lash settings. The CCS-1 has a longer duration on the exhaust lobe, which improves cylinder scavenging for better volumetric efficiency without creating a choppy idle. That makes the engine much more efficient at low to medium speed, and flattens the torque curve. Bump the compression up with a little bit of cylinder head milling, and the torque gets even better. 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!
I think all the members try to help in their own way so take it all in and make your own informed decision. Jerry's comment about needing torque has merit. The old truck has the aerodynamics of a billboard travelling down a highway. At highway speeds (60-65 mph) a 235 with a 3-speed overdrive (4.11 X 0.70 = 2.87 final gear equivalent) can/may use up more gasoline than a 261 with the same transmission at the same speed.
Oh yes, definitely. I appreciate everyone's help, and Jerry in particular has been very willing to help, including passing along his phone # to me to chat (which I fully intend to do one of these days). Maybe I should have worded my response better, but I certainly wasn't being argumentative if that's how anyone took it. Was just trying to say that I'm just looking to make the truck more drivable, reliable, and safe for enjoyment driving on weekends. I live in the country and want to take the truck further than just into town. The main road to get from here to anywhere is a 55mph speed limit, and I tend to annoy the others who are stacked up behind me when I'm only doing 45. I suppose my definition of "cruising" differs from Mr. Google, as my interpretation includes what many people refer to as "cruising at highway speeds"
The bottom line is the 235 enjoyed a nice torque line which saw near maximum torque around 1600 rpm stretching all the way over to 2800 rpm. So, one way to get more usable torque in a long flat range (without spending an arm and leg) is to use a 1959 camshaft...or one that mimics it. Good luck!
Just so happens my 235 is a '59, but it's out of a car, so not sure if that cam was any different.
As I understand they were the same, RB...although the car engine would have used hydraulic lifters and that cam would have had some design differences as a result. Net performance would be the same.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
What is your tire size, RBs36? That’s a significant factor here. The “torque plateau” characteristics of the later 235, as mentioned by Jon G/ Jerry, gives you quite a bit of leeway in rear end ratio.
But since you’re swapping rears anyway, might as well try to strike a balance between first gear and OD usability.
I’m not familiar with tires for the 17 inch wheels. I’d assume they are pretty tall.
What is your tire size, RBs36? That’s a significant factor here. The “torque plateau” characteristics of the later 235, as mentioned by Jon G/ Jerry, gives you quite a bit of leeway in rear end ratio.
But since you’re swapping rears anyway, might as well try to strike a balance between first gear and OD usability.
I’m not familiar with tires for the 17 inch wheels. I’d assume they are pretty tall.
They are 5.25/5.50-17. Coker shows them at 29.02" diameter.
3.73 rear and a 0.72 OD would have you square in the middle of the torque band rpm at 64ish MPH. And OD would still be usable starting at just a fuzz over 50 mph.
I suppose my definition of "cruising" differs from Mr. Google, as my interpretation includes what many people refer to as "cruising at highway speeds" 