TH350 Torque Converter Stall behind Dauntless

A question for all you guys running an automatic in your early CJ.

I'm trying to determine if the T-converter I selected for my swap is going to be adeqaute for off-roading. Here's why:

I came across an interesting article on the Pirate Board regarding the torque converter stall speed for an off-road buggy with a V-tech 4.3 and a 1.82 first gear automatic tranny. They started with an 1800 stall but with this low stall they couldn't even climb up a 60 deg slope. They ended up with a 3500 stall and said they would actually like 3000. The higher stall enabled them to launch much better and use their 4.3's 220-hp to its fullest.

This got me thinking about my soon to be set-up (Buick 225/th350/d18 w/ Terra's). The th350 has a 2.52 first gear. I opted for a roughly stock stall torque converter probably somewhere around 1600-2000rpm. Now, I know that my little dauntless doesn't have the near the power of the 4.3 (maybe 180-hp) so am I just asking for trouble w/ such a low stall?

Also, with the removal of the 225's heavy flywheel, are these engines worthy of making enough torque for off-roading?

Thanks again,
Ty

 

It seems to me that alot of the 225's torque is created by that heavy flywheel. Plenty of people use the 350 tranny with the V6 though. Someone who actually has one running will have to chime in here and give you the straight scoop.

 

I've always understood that a higher stall speed let the engine rev higher before the converter "locked" up, so with a 300 stall you would have to rev the engine like crazy to get anywhere. I personally went with the stock stall on my CJ, havent driven it yet to know how it acts, however I have driven an automatic Commando and with a stock converter it had plenty of pwer to climb things, actually suprised me how much get up and go it had with the 3.23 gears and being heavier than the CJ-5 I've driven for ages.

I would say the people that cant climb a 60 degree incline have other problems than stall speed on their converter.


All the heavy flywheel did was allow the 225 to maintain the torque when you placed a sudden load, call it inertia. The flywheel wasn't directly responsible for all the torque, it just let you dump the clutch at idle and the inertia from that 50 lbs would keep the engine from dying, by resisting a change in rpm.

 

Converter stall speed works kind of like this: Hold your foot on the brake with the vehicle in drive and hit the gas pedal. What speed does the engine RPM's rise to? The stall speed is related to where your particular engine actually makes torque. Pretend you are sitting in your stick shift jeep on a steep hill, or with a trailer with a load on it behind you. You wouldn't just slip the clutch out to get rolling. You'd also rev the engine up as you dumped the clutch to generate enough torque to keep from stalling. In an automatic used in a performance situation, you want the stall speed to relate to your torque curve in a similar fashion. Now, I have no clue how a Dauntless torque curve looks, and how you are actually going to be using your rig. Bumping up the stall speed isn't going to make it more fun to drive on the road.
Banks has a good page on converters that includes a link off from it regarding stall speed. It's kind of geared towards diesel trucks, but the theory still applies.
http://www.bankspower.com/Tech_understandtorqueconver.cfm

 

Thanks for info and the link. Very interesting article. What stall are you guys with TH350 behind your V6 running?
Ty

 

I used a T400 converter on mine w/5.38's had lots of low end grunt. might use a lighter one out of the 350 if I drove it on the hyway, might have better top end I didn't have overdrive.

 

Right on. Sounds like I should be in pretty good shape with the stall I've got. Thanks for all the replies.
Ty

 

Another thing to look at, is most hi stall converters are smaller diameter (read lighter) which also takes away from torque. Also stall converters generate a lot more heat due to slippage, so if your running the trails you better have a really good cooler.