Drivetrain HP limits

[lazyguy]

I am building a 400+ HP AMC 401 and am asking myself will the stock drive train handle it. I have 2 J-10s and I am wondering which one if any is strong enough for the 401. #1 has the TH400 with the QT-1339 t-case and #2 has a T-18 with a Dana 20 t-case. I have read up and both setups, as far as I have read, are strong but no one seems to give a limit for what they can take. Anyone have any suggestions and possible experience with this?

[Ryan]

205 and 300 are two gear driven, cast iron case tcases that are known as the strongest in the OEM realm. After that, you are looking at Atlas, Stak, etc. You can buy a used Atlas for a decent price though.

[chief1ton]

If you want brute strength, without the brutal price. your best bet is an np205. unfortunately the 205 has a poor reduction of only 2-1 (same as the d20) there is a 3-1 kit for it, but its not much less than an atlas.

[lazyguy]

Th400 will easily handle it, but you should consider a basic rebuild with a shift kit at a minimum. The QT "CAN" handle that power, but if it's not in top shape, you really need to rebuild it and install a new chain. Personally, I ditched my QT and am going with an Atlas & 700r4 combo. My hp is around 450, tq is around 525 or so on my 401.

Is there another t-case that is close to the Atlas strength but less money?

[lazyguy]

nevermind, I figured it out

[lazyguy]

This is probably a stupid question but does the Th400 to Dana 20 adapter work with a dana 20 out of a FSJ with the T-18? I only ask because when I separated my t-18/dana 20 combo a gear that is attached to the output of the t-18 came out of the t-case. I'm just wondering how does that work when you convert to a TH-400. Does the new output of the TH400 have that gear?

[lazyguy]

i know that I need to change the TH400 output and most likely will rebuild and shift kit it while apart. As for the D20 it will probably get the twin stick, a rebuild with a deeper low range and the upgraded output. Thanks for all the input and suggestions.

[chief1ton]

I run the th400 d20 combo. imo the d20 is stronger. however i have little experience with the qt. i'm running 39.5 with 4.88 gears in d70 axles F and R. on my third year with the d20. i have a twin stick in mine and regularly use it for front digs. (on my 5300 lbs rig) and have had no pro with it, thus far the d20s biggest weakness is the rear output shaft. there is an upgrade for it.

http://www.jeepfan.com/products/drvsus/aa-d20shaft.htm


So you know the d20 will not bolt to your th400 without installing a new output shaft. this will require tearing down the entire trans. might as well have it rebuilt while it's apart. (install a shift kit in your th400)

the d20 will also give you the option of a twin stick if you should decide to go that route in the future.

[fulsizjeep]

My vote is T400/D20. If fun means getting on it once in a while, I can hear brake cones getting the spline ripped out on a QT.

[Ryan]

The QT's weakness is from typical lack of maintenance, chain stretch and an aluminum case....but they were also used behind big motors in race trucks.

The D20 does have a cast iron case and is gear driven, but tends to fail from work bearings / adapters. When I was looking for a replacement case for my chero, I talked to several builders about keeping the qt, going with a d20, or going with something else due to the 450hp / 525 tq with 35's. The one common thing I heard was that the D20 wouldn't last too long behind that unless I dumped a lot of money into it. The qt was the same, plus it is an aluminum case and not gear driven (which I didn't like). For the amount that I was going to spend, I wanted strong case, gear driven and could handle lots of power (in case I added hair dryers down the line).

[lazyguy]

So a TH400 with the D20 would be the best all around combo? My QT is not in good shape.

[Brent]

I believe the Dana 20 is far stronger than a QT, I am not saying that a properly maintained QT isn't strong but a Dana 20 is cast iron and gear driven, I think it would be sufficiently strong.

[Ryan]

don't have as much experience with them, but from the various tcase builders I've talked to, the D20 is not as strong as the QT is. I've only had one D20 rig, and I drove it a total of 400'

[lazyguy]

Th400 will easily handle it, but you should consider a basic rebuild with a shift kit at a minimum. The QT "CAN" handle that power, but if it's not in top shape, you really need to rebuild it and install a new chain. Personally, I ditched my QT and am going with an Atlas & 700r4 combo. My hp is around 450, tq is around 525 or so on my 401.

What do you think about the T-18 and the Dana 20?

[Ryan]

Th400 will easily handle it, but you should consider a basic rebuild with a shift kit at a minimum. The QT "CAN" handle that power, but if it's not in top shape, you really need to rebuild it and install a new chain. Personally, I ditched my QT and am going with an Atlas & 700r4 combo. My hp is around 450, tq is around 525 or so on my 401.