school me on torque converters...

[jekbrown]

Ok, I'm getting ready to build a th400. Question is, what TC should I run? I'll have a mild 350 in front of it and a doubler behind it. Reverse Manual valve body from Redneck Trans, deep AL pan, high quality rebuild parts etc.

I've seen TCs everywhere from $80 to $375 (super blingin custom Art Carr...). What stall would be best? Right now I have a 1800rpm stall in my 700R4... and it seems like it takes a little bit to much RPMs to get my truck rolling in the rocks. I don't have a doubler yet, would a super low rpm stall be a problem when in double low? Do I want something closer to stock (15-1600?) or something over 2000 (seems more comon)...? What do you guys run? Are the $375 TCs really worth it for someone not competing in drag racing? Whats the advantage?

j

 

[sled_dog]

I got a 1900 stall convert from Summit. Reasoning was easier stopping. With the doubler and 5.13s I was worried about having the fight it with the brakes all the time. Of course I haven't run the setup yet to say how I like it. Problem of being below stall is it builds heat more. Gonna need to run a good sized cooler on mine. Don't think the Summit one cost more than $100, I forget now.

 

[55Willy]

I think a stall convertor is almost useless in a 4x4 unless you are running mud and need to be in the power ban, but then your running a huge cam that needs it. my room mates a 1972 k5 with a nice mild 350 but the PO put in a 2800 stall and it's just a waste, we're swapping in a stocker.


I'm swapping mine over to a manual becuase I didn't want to run a huge stall. be easier on the u joints.

 

[jekbrown]

cool. I'll have 5.13s and the doubler too. I figured lower stall would = more heat... not sure how big of a problem overcoming the brakes would be.. Ive heard it can be a problem... but anyone experience it? I'll have the big B&M stacked plate cooler on mine plus a remote oil filter...

j

 

[55Willy]

run a fan just for the tranny cooler and a tranny temp gauge, no worries.

 

[jekbrown]

bump. I'd like to hear from other people who have doublers with autos in front of them...

j

 

[ntsqd]

Can't help you on that application, but a suggestion: try to find an ORIGINAL converter from one of the GMC motorhomes. They had the highest torque multiplication of any TH400 converter offered by GM. The reason was a 12k lbs MH on 16's with the only R&P avilable for the TH425, a 3.08:1

 

[jekbrown]

not a bad idea there... tranny shops can rebuild used converters for you for not tooo much coin right?
any other doubler people wanna chime in?

j

 

[ryan22re]

i paid around $100 for my 700r4 converter from a local converter rebuilder. was like a $20 core (i had one). got a 1800 rpm stall too.

most rebuilders (good ones at least) can build it with most any stall you ask for.

ryan

 

[BadDog]

As long as you have regeared to match your tires, and you've not built a high rpm motor or mud/sand truck, I think the stock stalls are pretty much right on. I've run a diesel converter (gets tight below or around 1000 rpms) and stalls up somewhere in the 2k+ range, and the approximately 1800 (rated, actually "stalls" a bit lower in my TBI truggy) I've got now seems pretty close to my ideal.

BTW, be carefull when dealing with "stall" ratings, you need to know what it's "rated" for if you want to actually be able to predict how it's going to work. A converter that stalls around 1800 with 250 ft/lbs will stall (guessing) around 2200 or so with 350 ft/lbs. So "stall" rating is directly proportional to torque input, but not quite linear it seems...

 

[smalltruckbigcid]

Here's a couple of terms to keep in mind:
stall- the highest engine rpm that is allowed when the driveline is locked, (stepping on the brakes and throttle at the same time)
flash- the rpm the engine jumps to immediately after you release the brakes. If this is to high it makes the truck jumpy under power, but you want some flash built into the converter.
slip- this is what makes converters so expensive, make the 'verter stall to a certain rpm usually means some slip at higher rpm's. To much slip eats fuel, raises heat and is a general PITA. The more torque your engine has the more the slip problem shows up at higher rpm's.
For my 500 caddy I have an 1800 stall that flashes to 2400 and has less than 5% slip (I haven't installed it so we'll see) from ATI for $250. iirc.
George