The Stovebolt Site Forums The Shop Area Driveline 46 3/4 ton rear end swap

I'm apparently a very bad at composing search criteria. I'm trying to find threads related to rear end swaps for 3/4 ton 8 bolt rear ends. I'm pretty sure I'm going to go with a full pressure 235 but want to change the rear so I can get up to freeway speeds. I found a thread discussing pumpkin rear ends, and a brief statement about 14 bolt rears fitting right into the '46. I've found a 14 bolt, 8 lug rear but it has a 3.73 ratio, which I'm thinking is too tall.

Will any 14 bolt rear fit the '46? is the 3.73 to high? HELP!!

Joe

I think 3.73 ratio would be fine, unless you have tall tires. All 14 bolt rears are not the same. Since you have a 3/4 ton truck, you need to mount singles. Wheel mounting surface(wms) to wms is what to measure. May not need to be same, just so tires fit in the wheel well. May have to relocate spring perches, both width and to get correct pinion angle.

There are many posts on here about doing this, may have to get dually axle from C and C to fit, for example. Grigg on here will probably update this.

Look up and read past posts to educate yourself.

Ed

Here's some info about 14 bolt swaps.
It's mostly geared to 48-54 models but most all of it applies to earlier and later models too.
Just measure your spring center width and original axle width at wheel mounting surface, compare to notes in this discussion.
https://www.stovebolt.com/ubbthread.../14-bolt-axle-swap-info.html#Post1249600

Ed and Grigg,

Thanks for the quick replies. I'll check out that post and look at the others.

Joe

the reason I asked if the 3.73 was too tall was because of a thread I was reading that indicated that going from the stock to a 4.10 was "too much" and recommended going to the 4.53 gearing. I've located a 14 bolt for $200 but the owner doesn't know what the ratio is. I'm thinking about taking a look and removing the cover and counting the teeth. It looks to be in good shape. It's a single wheel unit. The one with the 3.73 is a dually and is pretty close to me so I may take a look at that too since it sounds like it will work based on the link that Grigg sent.

thanks again,
Joe

You can do the math and see what RPM you'll be running at what speed with which gears.
http://www.onlineconversion.com/bigger_tires.htm

I have run 5.14, 4.56, and 4.10 in my 1 tons (different times) all with tires 32-33" tall and direct drive transmission, and either 235 or 228 engines.
5.14 is just slow, plenty of power but not much road speed.
4.56 is better, still wish for a faster gear, only occasionally wish for more power.
4.10 is pretty good all around, usually fast enough, usually have enough power for high gear on most hills, but not much extra. Down shifting is always an option.

3.73 I have not used, but will try it next. I suspect it's geared to fast for the little 228 in a truck that weighs 4,500 lb or so. With more power 3.73 might be a likable gear ratio on a 3/4 or 1 ton, but stock I bet it's a stretch unless your truck is light and you live in the flat land.
With increased speed stopping becomes even more important, the old brakes might not do well enough, and otherwise your suspension and steering need to be in great shape.

Your situation will vary if any of the following are different than mine; road conditions (hills), driving style, engine, transmission ratio, tire diameter, and vehicle weight.
Use the gear calculator and adjust your expectations and plan to suit your situation.

Grigg

Hi Grigg,

I'm probably going to switch out the stock 216 for a rebuilt 235 so there should be a little more power. It's also a stake bed so I can take off the stakes and metal corners to make it a little lighter. Right now it has the stock transmission in it but I've also located a T5 transmission that I may purchase.


Joe

Anyone know what the stamped number on this rear end mean? I've tried to look it up on several sites but haven't found anything.

JoeR
I swapped my pumpkin from 5.14 to 4.10 on a 49 Advanced Design. This gave 6 mph more at 50 mph. So my top end gained 6 mph. There was no noticed loss of power. Just sayin.

Don