The Stovebolt Site Forums The Shop Area Driveline Dream Rear End Ratio and 3D Printing

Additive (3D printing) manufacturing of gears is getting better and better. Some analysis have it on par with traditional forged parts.

So if you could get any ratio your heart desires for a 3600 rear end, what would it be? Our 3100 brethren can still get the 3.57:1 kits I believe but I can't find anything beyond a 4.11 for the 3/4 ton. What would you order up from the 3D printer?

I ran a 3.73:1 ratio from a Ford 3/4 ton in a mid-1970's Dana Type 60 housing for a GMC, and put it in a 59 Burb behind a SM-420 and a 307 V8. It pulled everything I chose to hook up to, including a 22 foot 2-axle camp trailer, or a big Case farm tractor and all the accessories such as a plow, grader box, disc, and a few other implements, and still kept up with traffic on the interstate. Unloaded and carrying the family around, it got pretty decent gas mileage, also. if a ratio like that was available for the Chevy 3/4 ton axles, it would be just about ideal.
Jerry

3.07 or 3.08 in the 1/2 ton is excellent if (and only if) you are careful with the gear ratios in the T5. If you do your homework cleverly, you can have a 5 speed with the first 3 gears matching the original overall ratios in the AD truck. Important? Only if you want to use it like a truck. Then your 4th gear becomes your first "overdrive" and if you have 3.07 will drop your rpms by ~25%. If your 5th gear is .86, then you'll be good to go. If your 5th is .72, your engine will lug and you won't like it a bit.

In a 3/4 ton, my question would be the same. How do you plan to use it? If as a truck, then as Jerry said something in the 3.73 range is what I'd think would be good. But again it depends on the transmission gear ratios to a big degree. A few people told me a 3.07 rear wouldn't work, but with the gear ratios I have no driver would ever know the difference from the stock 3 speed until he hit 4th gear.

The best tool I’ve seen to calculate gear ratios vs RPM vs MPH is the site www.4lo.com check out the gear calculators.

The 3.73 with an NV-3500 5 speed transmission would give you truck capabilities commensurate with the rest of a 3/4 or 1 ton vehicle, plus good highway speed. Then all you'll need is an engine with enough torque to pull an overdrive gear like that- - - - -maybe a 400 small block, a 427, or a 454?
Jerry

No one answer, a lot depends on the terrain. Was running a 3.54:1 (dana) in my '60 w/ 235, was too high geared to pull hills good in direct. Now running 3.73 pulls hills much better.
I've got a K2000 (old body GM400), 5.7 / 4.10 10.5 full floater, NVG4500 , pulls storng. Wouldn't want any higher gears.

Tire height plays a part here also.

Just keep the stock gears and put a BW Overdrive in it then you can pull down the house and then cruise at 70 on the highway 🤙 When its locked out it acts like a normal low gear truck which is perfect to tow or haul anything.

I like the overdrive suggestion. I had a '65 impala with 3-speed and OD and really liked the combinations especially going up and down the Rockies.

I recently built a Muncie/BW R10 overdrive for a guy in New Zealand. I installed the HD close ratio gear set (Corvette/Pontiac) which has better ratios than the standard set up. He is using it in a 65 C-20 with an overhead camper. He upgraded the engine to a 350 and retained the corporate 4.57:1 rear end. It works well with that combination.
Fred

While 3D printing gears that can handle power or torque are still a dream..........powder metal gears are common place in transmissions and driveline parts.

https://www.gknpm.com/globalassets/downloads/sinter-metals/english/drivetrain-products-english2.pdf/

https://atlaspressedmetals.com/stru...Z2rvm6gIVjsDACh3MCA2kEAAYAiAAEgKGS_D_BwE

My '49 3600 is for light work, with no towing. So it's mostly about getting comfortable highway speeds. Prior to me it had the 216 swapped out for a 1955 235, which I prefer to keep. I like the straight sixes a lot. I'd like to re-gear the rear, not change it to something altogether modern. The BW Overdrive is intriguing depending on how it's mounted.

Tires: I ordered up the 16x6 AM20766 Dexstar wheels. With 235/85 R16's the diameter works out to 31.7" which is 1" greater than the optional 17" wheel/tires you could originally order. The fenders look like they could take a bigger diameter still, but as wheel diameters go up, so do widths (and backspaces) which is the killer. 8R 19.5 tires are just 5.25" wide and yield a healthy 33.1" diameter.

I can provide you with all the information you need about BW overdrive transmissions and how to make the conversion.
Send me a PM.
Fred

If you're planning to do real truck stuff with your vehicle, a B/W overdrive trans is sending a boy to do a man's job. Get a 3/4-1 ton truck 5 speed with OD on 5th. gear.
Jerry

Doing a 14 bolt swap or other rearend swap would probably be a better optiin than trying to re-engineer a 70 year old axle design that hasn't been manufactured in 50 years. Just a thought.

There are a number of companies that will build custom axles for one's needs. The off road guys even have full float kits for 9" and 8.8 rears.

Thee are plenty of Dana type 60 axles out there, and all sorts of replacement gears in a wide variety of ratios are available for them. There's no point in reinventing the wheel, especially with a manufacturing process that's marginal at best.
Jerry

Anyone know if there is a CAD file floating around out there for the 3/4 ton rear end?

If you want to get serious about this, these are the people to contact https://ptggear.com/

I've though of this for a while, but the issue is that their are primarily two camps of people that want these rear axles and different ratios.
1, us, the guys that would like some more highway friendly gearing (3.30-3.70ish sets)
2, rock crawler and mud bog guys that want to find the elusive 5.83 sets and would probably want custom 6.17's or something

Getting a custom set made is possible, but I haven't gotten any quotes yet.

The biggest financial issue you will probably run into is that you will probably need a few thousand sets made to get the cost per unit low enough for people to consider buying a set. Then you have to wonder about how many people would actually buy a set.

If I was independently wealthy, I would totally make some 3.50ish sets and sell them for cheap <$500 to whoever was interested and just take the financial hit because I love these old trucks and would like to see more of them used for everyday driving, but I'm not.

There are enough options with modern ratios, OD trans.' Brownies, etc., that one should be able to figure out what would work best, then the true answer would be road habits with and without loads.

Ed

There's most likely a good reason that replacement gears, and/or non-standard ratios aren't being manufactured these days. The old law of supply and demand, plus the likelihood that no manufacturer with any sense at all would tool up to produce parts for such a small, specialized group of customers comes into play. There's probably a bigger market for buggy whips, and whalebone-reinforced corsets than there is demand for those gears!
Jerry

I’d buy a 3.7 - 3.9 gear set priced under $1k
I’m going to end up having that much into a Dana 60 or 14 Bolt swap anyway.

Buggy whips and whale-bone-reinforced corsets. Interesting combination of words right there...
There is definitely a more lucrative market for pairing those two items together in certain circuits of society.
May have to borrow the boy's 3D printer...

I've seen quite a few of one of those items in John's neighborhood- - - - - -if the other is as much in demand there, it's likely to fit the "Don't ask- - - -don't tell!" category!
LOL!
Jerry

Wow $1000 for a 3.90 third member , food for thought !

John

I did follow up with the custom gear company you suggested, out of curiosity.

Ballpark estimate from the PTG guys was $15,000 per R&P, and the RushGear guys were about $10,000. You need to send them a CAD file or an actual R&P set for a more exact quote.