T-14 vs T15

Swaping in 304 into my CJ-6. I have the t 14 / dana 20 that was in it with the 258 AND the t 15 / dana 20 that came with the donor Jeep. What makes the t 15 better/stronger than the t 14? It looks like just different gear ratios....am I missing anything? Yes, I know 14s where used with 6s and 15s with 8s, but what about the unit is stronger? The input shaft? gear sizes, bearings.....
Thanks

 

Well, you have an example of each - why not put them side by side and tell us? The T-15 is clearly stronger, easily surviving behind the Buick 350 and AMC 360 in both J-trucks and Wagoneers.

The T-15 has better ratios IMO - 2nd is too low in the T-14, making it less useful as a passing gear - but that shouldn't affect the durability. All the oterh ratios are about the same.

 

I've had them both, but had an overdrive with my T-14, Dana 18 combo.
I lost some syncro gears in my T-14 with the V6, but have had no problems with my V8 and T-15.
I'm not sure the exact gearing between the Dana 18 and the Dana 20, but the Tera-low kit is actually cheaper for the 18.
Dana 20's are much more common though, and can be found from 72-86.
If I had the choice, I'd ditch them both and go with a proven strong T-18 and a Dana 20 case.

 

The T-15 uses larger gears, bearings, synchro assemblies, and counter gear shaft. They also have more contact area between the synchro sleeve and the dog teeth on the gear so less prone to jumping out of gear under load. Nickmil.

 

Yesterday and today, I drained the liter or so of water from the donor T-15, completely took it apart and used brake cleaner and compressed air to clean each part before I put it all back together and paired it with the best of the 2 bellhousings, dana 20s, clutches, etc of the 2 engine/drivetrain combos. So after indepth study and having the other trans open as well, heres what I found:
The T14 has a case length of 8.75 inches while the T15 is an even 10 inches. The cover on the 14 has 6 screws while the 15 has 8. That extra length is because (as said) the gears and such are BIGGER. The shift forks are 3 inch and 3.5 inches. The width of the gears are 3/4 on 14 and 1 inch on the 15. Based on what I saw, I'd say every bit of 25 % bigger and stronger. The throwout bearing collor has only 3 screws on the 14 and 4 on the 15. The Dana 20 bullgear is the same size, but there is a difference in the shaft size and spline count. Seeing this also confirms what I saw in the catalogs...that they share almost none of the same parts. They remind me of when I saw the difference in the diff/ring and pinion sets of the Dana 30 vs the Dana 44 axles. They look the same in parts and construction. It's clear that they are made by the same company, but wow, one sure is bigger and stronger. So thaks for the replies. They were correct.

 

thanx for starting this thread.........went over a side by side comparison yesterday with a T14 and my T15........and you guys are right, as always