flyingd

I was talking to a transmission guy about a TC and he thought, for towing, that I would want a high stall tc. I thought I had read, for our cummins, that we would want a low torque TC.

Help me tell the guy why.

Thanks

joem

To put simply, the Cummins runs happy at crazy low rpm- the cummins starts to defuel and hit redline where my F250 gasser warms up at on a cold engine so gasser auto tranny knowledge is thrown out the window with the cummins. 400 RPM lower than stock is about ideal and dont forget to get a tripple disk converter lke a goerend or ATS plus a new valve body to stiffen up the shifts as when the trans does a shift the cummins doesnt really want to change RPM and the massive torque is rough on these 47RE's
Joe

j-fox

It sounds like he races or builds trans for racers.

Tell him the cummins make peak torque before 2000 rpm and when you add fuel/power the peak stays there. It isn't like a big cam gas motor where the torque peak is at 5,000 rpm.
if you motor is close to stock it doesn't even fuel past 3000.

If he still doesn't see it, find a truck with, say, an 1600-1800 stall converter. Take him for a ride.Then then again with a stock converter that slips to 2200.
Both with trailer on them too.

When I had my 95 I went thru this with my trans guy. He laughed and argued. I let him at his expense play with 3 converters.

Guess what, his converter builder and himself said the tighter they made it the more it liked it.
He said he had no idea that motor was such an OX!!! And he thought his navistar was very powerful, but the dodge would pull it anytime.

Don T

A LOW stall was what I bought and a single disk all billet .I don`t think triples are needed for under 400 hp.My truck pulls my fiver way faster off the line than it did with the stock TC. I could slip the tc on the 3rd locked shift real easy and now it goes ahead with not heat or slipping. I pull 10500 fiver and I`am real happy with my TC.

toms73novass

I put a lower stall in mine and it did NOT like it as much as the stock stall. I went back to a stall that is closer to stock.

I did not like the way mine wanted to "take off/ fight the break" with a higher idle, or would want to lugg if the idle was lowered.

However I would definitely not do a high stall....

greendodge

I have a Goerend converter, 300 rpm lower than stock in a 1st gen w/727. (non lockup). I love it. no excess idle creep. Lower rpm on highway. I'll use the low stall converter behind a mild Cummins every time.
Don't even think about a high stall.Your tranny guy is thinking gasser logic.
Ray

dieseldemon

You want the stall speed between 1400 and 1600 on the 12v engine

95ram

I personally like the low stall in mine. I do have to stand on the brake a stop light, but it gets my trailers going without the RPM's getting out of the TQ range like stock did. On flat ground it does 12 mph at idle.

Turbo2gnx

I used a modified tq with the stal at 800rpms single disk. The truck was a beast! 1st -3rd was sideways. I bombed my tranny and now I can't find anther company to build me a tq that low of a stall... now I'm using a 1100 stall, its garbage.. the reason I posted this was, I didn't see anybody that experienced a very low tq... I pull a 20ft trailer with a welding machine and steel beams all day, the weekends, the track.... well not anymore, in need of a 600-800 stall tq...i bought it from DTT years ago, they don't deal with the same builder... I'm at about 550 up and around 1,600 ft lbs of tq. Stage 5 injectors, 77/14sledpuller turbo, comp edge drag, and all billet tranny with flywheel upgrade..

patdaly

Call Dave Goerend, I am sure he will build you exactly what you want. Sounds like you have your old converter still?

AlpineRAM

Well, depends on what you want to do- and if smoke is a concern for you.

If you go low stall, too low stall to be precise, your truck will want to push you through each intersection, will either smoke while taking off or be about as agile as a glacier when trying to accelerate.

If you go to a higher stall than stock... you will need an engine built for that, meaning different pump, twin turbo, camshaft, conrods, and a lot of other things, to move max torque up in the rpm band. (And to be able to put out serious hp above 5k rpm.. rather extreme build for a daily driver.)

About stall speed- the stall speed describes the rpm achieved with the truck at standstill and the accelerator pedal on the floor.
Even for the same converter the speed will vary wildly with any tuning, bombing or modifying the engine.
With my truck, for example, the same torque converter had a stall about 1500 rpm stock, and about 2900 rpm after the engine rebuild.. some parts may now not conform to the strict specs of Cummins Co.

So I needed a TC with a stall matched to the torque curve of my built engine, something that Daimler-Chrysler did not supply with the stock vehicle.

In my opinion the best course of action is to talk to some companies that have experience with these vehicles, especially with the Cummins diesel, and to be completely honest about the intended use of the truck.

texasprd

I considered a lower-stall converter myself. When my truck was down last summer for a transmission rebuild (caused by a cooler-line rub-through). I asked my transmission guy about the low-stall converters, as they claim to make better use of the Cummins' torque. He replied that a few of his other customers with Dodge CTDs had tried the low-stall converters from the rebuilder he uses - they worked fine until everything warmed up, at which point they would get too tight and cause stalling when stopped in gear. That was a deal-killer for me. YMMV

AlpineRAM

Idon't really understand the fascination with stall speed- the interesting part is the curve described over delta rpm and torque.

There are a lot of less than satisfactory converters that have a very low stall, but no torque multiplication to speak of.

Then there are converters that do have a good torque multiplication number at reasonable delta rpm, and a good efficiency at low delta rpm.

These converters will stall a lot higher than the bad ones, but- they will multiply torque at a factor of more than 2.2, so if you get on it the truck will rev to max torque rpm and the converter will give you more than double of your engine torque, put it into the transmission and in 1st gear it will put your eyeballs onto the headrest regardless of what you may have hooked up.

On the other (bad) hand you have converters that are plainly inefficient, that will stall low, and will actually do a torque reduction. So, with the converter taking a lot of torque at low rpm it will not let the engine develop torque, and then it will "multiply" it by 0.8, effectively giving the "good" TC about 4 times more pulling power from the line.

In my opinion there is so much to TC design, to adapting shift points, and to tuning an engine to make a good package for the intended use that reducing the discussion to a number like stall speed is at least problematic, or even dumb.

saggonwaggon91

And this is why i prefer to have the varible stall unit in my pick-up, adjustable with my left leg.........lol

AlpineRAM

Yep, variable stall, but no torque multiplication...

(And, thinking of teaching a teenager to drive a stick shift, it seems to be a lot easier to build an AT with a fitting TC- at least the AT will not confront you with internet memes )