Torque converter tech.

[broncoman6524]

So I was trying to find a lock-up kit for my TH400...not going to happen.

I thought about whether the torque converter could help my mileage, and part throttle response. As far as I know the converter is stock, but the tranny has a shift kit, and HD clutches/bands.

The way stall speeds were explained to me were at the "advertised RPM" the converter flashes and kicks in more. I found a converter on summit with the flash RPM at 2K which is where the truck cruises at.

Would this be something that would help at all? I know in the mud it would help me, but I'm not 100% about the street.

http://store.summitracing.com/partd...865426+4294889568+4294739905+115&autoview=sku

I know the truck has alot to do with how the converter perfomrs... It's a 84 blazer with a GM 290hp crate, air-gap intake demon carb, MSD. 208 with 10bs lockright rear, and 33 BFG A/T.

 

[odin]

I would not recommend a stall speed converter for your truck.

A 2K stall summit converter would probably stall at about 3K in your rig, unless youre running 4.88s. The stock converters stall at about 1200 rpm and when you ad larger tires and not enough gear that stall speed increases.

 

[Mike D]

I have a 1981 Chev 3/4 ton truck. When I converted my truck from Sm465 to Turbo 400 the shop who rebuilt the T 400 gave me a torque converter that had 1200 stamped on it. The truck would pull at 1200rpm. It ran OK but a little doggy behind my rebuilt and modified 350. The engine came alive at 60 mph and above. I replaced the torque converter with one manufactured by Jet Engineering ( they use HD torrington bearings ). The stall speed is 2400rpm. The engine comes alive almost from a dead stop. When I stab the gas from a dead stop I am pushed back into the seat (feels like a jet taking off). There is no wheel spin (33" tires and positraction) just acceleration. I am very satisfied with this torque converter. You discussed fuel economy. With the SM465 I got 10 mpg, with the stock converter (1200) I got 10mpg, with the 2400 converter I get 10mpg. Apparantly when you let the engine run in its sweet spot the improved efficiency offsets the increased rpm required to move the truck. By the way the 2400 torque converter has been on for 4 years.

 

[dyeager535]

There are "switch pitch" converters that change the stall speed, but I'm not sure how easy and cheap they are to get ahold of. Also not completely sure if they require a specific TH400 case or not.

For clarification...the switch pitch converters actually change the angle of the blades in the converter for good characteristics for cruise, and good low end power. With more thinking, that may be a bad thing in a truck if used at low RPM, since high stall equals high heat, which equals problems.

 

[BILTIT]

Torque convertors are a touchy issue.

The stall is the rpm where the convertor begins to couple, prior to the stall rpm it is multiplying torque. You want a convertor to flash (correct word for stall) to a rpm which your engine is producing most of its power. The cruising characteristics of the convertor depend on the efficiency of it and not so much about the stall rating.

You can get ''tight'' convertors which act like a stock peice until you give the skinny pedal then they flash to their rated rpm, but it is usually a custom piece=$$$.

I have one in my 74 ventura with a 455 pontiac. I drive around the street like its a normal convertor, even wants to push the brakes pretty good when stopped at a light. When i want to givver i put it down and the convertor flashes to 3200rpm (getting a restall to ~4000 this winter).

It has very good coupling up top too, only 5% slip at 110MPH which is as low as you can find anywhere.

Efficiency is much more important then stall speed.


I am thinking on this aswell as i am putting a torquey 400 pontiac in my truck and not sure what to do for convertor.

http://www.autogeek.com/news/Transmission1.pdf
http://www.tciauto.com/Products/TechInfo/torque_converters_explained.asp

 

[broncoman6524]

I guess I should have mentioned it has 3.73s.

I had read somewhere about the "Switch Pitch" converters, As you said I got lost and it seemed way to complicated and too much money.