Engine/Transmission (1998.5 - 2002) 98.5 Torque Convertor Stall Speed ?

[John - K5AWO]

I did a search on: torque convertor stall speed



without any relevent hits.



Anyone know what the stall speed is on a stock TC ?



1) If brakes locked, is there an upper RPM limit before things break?



2) What should the rpm drops be for each gear if holding a steady 1700 rpm? 2100 rpm ?



3) Is there a specific test procedure to determine if the stock TC is good vs starting to slip too much?



At 1700 rpm, mine drops about 100 rpm/shift and about 500-600 on OD shift.



At 2100-2200 it seems to drop about 125-150 rpm and then maybe 500 drop on OD shift at which point the first really effective acceleration pull begins.



If I push the rpm to 2600+ it seems to be a needless, ineffective exercise and produces no real advantage to just setting at 2200 rpm and waiting for the truck to catch up with what I want.



On one occasion I locked brakes, pushed rpm to 1700 and launched to compare the result with a normal idle condition, release brakes, and go. The truck did significantly better, but if practiced regularly is it going to kill the TC or break something ? #@$%!



Comments?

 

[mike r]

The advertised stall speed is 1600 rpm and yes you will fry it if you keep doing what you're doing. The actual stall speed in use is much higher when used for towing, hence the need for replaceing it with a good aftermarket unit. When I replaced mine last summer, the lockup clutch was fried.

 

[John - K5AWO]

I forgot to mention that I previously owned a '98 12V 2500 CTD. On that truck, I was thoroughly impressed with the way it pulled in all gears. seemed like the stall speed of the TC was much lower and a lot firmer with each shift.



I'm just a tad bit disappointed in the way this 98. 5 unit works. I haven't pulled anything with it yet. However, when I bought the truck last December with 87k miles on it, it came with a goose neck hitch mounted and a 10k # receiver hitch. So obviously, it has been pulling something. The previous history is an unknown so I have nothing to go by.

 

[Lsfarm]

TC Stall speed

Hi John, the stall speed of a torque converter is hard to nail down. For a given HP and Torque, you can get a given stall speed, but add HP and torque which is so easy with our Cumins engine, then the stall speed is much higher than before.



A stock engine will usually not exceed 2200 rpm in drive with the brakes locked, but add a few hundred ft-lbs of torque and then you will see 2700+ rpm kick up the power some more and you can hit redline on the engine and be at a standstill and boiling your ATF.



The Stock torque converter is designed for gas engines with effective power/rev ranges over 5000 rpm. Not designed for the Cummin's torque and rev range.



You are in AZ, so do a search for Fred Swanson, and look him up, he's in AZ somewhere. Get a ride in his truck, to feel what a real torque converter feels like. You won't believe the difference.



The difference between your old truck and the new one may be just the difference in the power the engine makes, or the TC in the new truck may be sloppier. But all stock TC's are trash behind the Cummins.



Pm me if you wish.



Found a link for you:



http://www.desertdieselparts.com



Hope this helps, Greg L

 

[Big_Daddy_T]

I remember reading some aftermarket companys propaganda and they claimed it stalled at 2400. I was able to hit 2400 with a very heavy load before it began to move. So I assume its over 2000. On top of that the efficiency is crap.

 

[juicedcummins]

Mine was 2000rpm with 275's under the hood. Then I switched to a BD lowstall:-laf and the stall speed went up to 2100rpm. After many calls to BD :-{} I decided to put up with it. . After 15k the lock-up clutch went out Then the Suncoast went in and the stall went way down to around 1700rpm and the Bd replacement went on the shelf to collect dust.



Note: this BD tc was an early model for the 24 valve and from memory it was stamped 215LS.