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Hi, looking for some advice. My 57-3100 has the typical 3 on the tree 235 with a 411 gear. I would like to be able to drive it on the highway without the engine being pushed to its max. From what I've read the most I can get is around 60-62 mph which will not meet my needs. I'm no mechanic but it seems I have a few options without changing out everything. (Engine, tranny , rearend) One would be to put in a 4 speed transmission so I would have more speeds to grind through or the other would be to change out the rearend to a smaller ratio, ( that number I haven't figured out). Does anyone have any experience with this. My goal would be that I could use the truck as a true daily driver. Thanks Kevin

3rd gear in your 3-speed is straight through, same as 4th in a 4-speed (most of them) so, if you are going to change the tranny, you need to go with one that has an overdrive.

Yes, you can change out the rear end (or just ring and pinion if you can find one to fit). Depending on how much faster you want to go, 3.73 may get you there.

Taller tires may also fit and get you a bit more speed (how much more speed depends on how tall).

You can also look at a Ranger overdrive unit. They go in front of your transmission, between the bellhousing and tranny, that is probably a lot more than swapping out the rear end though.

i put a 3.38 R&P in my 56 3100 and it works great. of course I don't really haul anything in it except a couple of bags of mulch now and then so I don't miss the low gearing to launch from a standing start. the RPMs will be about 18% lower for the same road speed than the gears you have now.

"My 57-3100 has the typical 3 on the tree 235 with a 411 gear."

Your standard rear end was 3.90.

As tomctomc posed, a 3.38 Ring&Pinion swap is possible.

That might make your 3-speed transmission's first gear a little high, but it would nicely lower RPMs at higher speeds.

"With great speed comes great responsibility". Make sure your brakes are 100%, then go for more speed. A 3.38 rear gear swap would give you everything you are looking for.

Kevin, with these assumptions; 28" tall tires, 2,600 rpm and 4.11 gears you'd be running 53 mph in high gear.

With everything the same except..... with a T5 transmission with a .72 overdrive (5th gear) transmission you'd be going 73 mph.

Lots of info on the swap, search is your friend.

Good Luck, Ron

I put 3.38 ring and pinion gears in my '59 and then changed out the three speed with a granny 4 speed. I love it now. Second gear in the four speed is a little lower than first in the three speed so it takes off easier and reverse is the same as granny which is great. Reverse on a three speed is always so fast that you always end up just slipping the clutch when backing up unless you need to go backwards really fast. I can cruise easily at 65 mph now too.

I didn't realize that the 2nd gear in a 4 speed was lower (higher ratio) than 1st gear in a 3 speed. That is what makes what you have very usable. Good find!
I had a 3.08 with a 3 speed and it was a total slug in first gear.
Carl

I think he meant that 2nd in the 4 spd is now lower
because the rear end gears were also changed. Jeffrey

No, second gear in the granny four speed is a little bit lower gear than first in the original three speed. It doesn't matter what the rear end ratio is. Every three speed transmission that I ever had, had a first gear that was too high in my opinion. I don't know what the ratios are but I think that third gear in the granny four speed is a little higher than second in a three speed. High gear is 1:1 in either transmission.

According to the 1955 Chevy Truck Shop Manual:
SM420 4 speed: 1st 7.06:1, 2nd 3.58:1, 3rd 1.71:1, 4th 1:1
SM318 3 speed: 1st 2.94:1, 2nd 1.61:1, 3rd 1:1
Fred

I stand corrected. Third gear in the four speed is a little lower than second gear in the three speed. I guess the bigger gap between the two gears threw me off or as my wife likes to remind me, I was just wrong.

Gene, while I am sure your wife would be beside herself with joy when she hears you admit that you were wrong, the insignificance of the 2nd and 3rd comparison does not take away from the significance of the 1st and 2nd comparison.

You can always go with a Borg Warner electric overdrive behind a 3 speed. I cruise 60 mph +/- at 2000 rpm with mine. Should be a straight swap with what you have now, no drive shaft changes either.

I agree with Moonlight and it was mentioned in a previous post.
The factory 3sp OD trans is a proven way for better highway performance. I have rebuilt and installed many of them.
As stated there are a number of ways to attain better highway speeds while getting better mileage and causing less stress on the engine. Do a cost comparison of all options and then come up with the best one to suit your needs.
Fred

First in the 3-speed is 2.94.
Second in the 4-speed is 3.58.
It's a big difference and the main reason I switched from the 3spd to 4spd in my 216 powered truck with 3.55 rear end. It was a dog starting out, made worse by the 30-inch diameter 215-85-16 tires I had on it. Switched tires to something in the 28-inch range (like original 6.00x16 had) also made it better.

Can even tell a difference in the intermediate gear, which is 1.68 in the 3-spd and 1.71 in the 4-spd.

I agree that a 6 cylinder powered vehicle as owned by Skooter and others need a lower gear to start out. Changing the rear end ratio to get more top end can create a situation as described.
This does not necessarily apply to V-8 powered trucks.
My 56 has the stock 3:90 rear end, a garden variety 350 engine, and a 3 speed overdrive transmission. I rarely use 1st gear starting out except on a hill, in fact it has a faster take off using second.
I only have to shift once to get 3 speeds with a good top end.
Another advantage to the 3sp OD is by using 2nd OD on hills or with a load. It is a mid range speed that really pulls well.
There is no one size fits all when it comes to the best
drive-ability.
Fred

Yep, especially the AD trucks were not well tolerant of single changes such as swapping the 4.11 for 3.55. You lose engine braking you always took for granted down the backside of hills. That was the big thing I didn't like. Never did wanna go the disc brake route, but it's the kinda thing that has to be considered when altering the magic 216/4.11 combination.

T-5

I have 1954 235 w/dual carbs and exhaust, and a 1979 T5 and Nova 2.73 gears rear end. Can up to 80 with ease but just got back from HQ and I had to go through the mountains and the gears are too low numerically shifted a lot. I averaged 22 mpg for 1700 miles. I live in flat land Indiana and my trips to KC every year it works fine.

Hey Ron, what size tires are you running?
2.73 gears are definitely highway gears.
Shorter tires would help.
Regardless of all that, the T-5 is a beautiful thing to have so at least you have the option of more gears to choose from to drop into in the hills.
Carl

Rear tires are 235/70/15 radials. Most long hills I just shifted into 4th. IN the Shenandoah National Forest there was a lot of shifting. Short steep hills and curves. I got the nova rear end almost for nothing. My brother-in-law's uncle had the rear end and his father had the transmission.