Spragless Convereter Pros and Cons

April 10, 2008, TCRA Email Forum

I would like opinions on the advantages & disadvantages of using a spragless converter in drag racing applications.

Rob Hans

Consistency Mark Mustard

The upside is that they CAN’T break LOL

They are consistent

Some of the fastest equipped cars in the world are spragless.

There are applications when a sprag is a must and applications where
spragless is best. Depends on the vehicle combination

I think Ken Kelly needs to jump in here 🙂

Joe Rivera

I’m sure that Ken can explain it better than I can but there is a two sided statement that follows the spragless stator converter. “They aren’t as fast, but THEY ARE QUICKER”. Therefore the lower ET and consistant runs with BIG horsepower makes the spragless stator converter the overall winner.Don Randolph


I stand corrected….they(spragless) are usually quicker (ET) than faster
(MPH)but it is usually ET that wins races.

And in the right combination they are also faster (MPH) in certain
applications …usually very high horsepower 1800 hp & UP. And in those
applications we have tested back to back and no discernable difference in

In lower horsepower combinations….that is a different story

Come on now Ken ….fill us in.

Joe Rivera

My experience with Spragless has been……Drag Racing if the sprag did not slip before than the 60 ft. times are the same but MPH is hurt by 1-3 mph. In a endurance application were the sprag in the converter would normally overrun, we see about 10-15 degrees more heat on average, but man it gives us great piece of mind because in high horsepower stuff the sprag eventually starts to slip.

Dean Kuhn


First off ….welcome to the TCRA. I am glad to see you have joined. I
hope it is everything you hoped it would be. The forum is new and is just
starting to get rolling. Thanks for the response

When you say Endurance ….are you talking Off Road Racing like Baja stuff?
We don’t get to see a lot of that stuff. Can you use a spragless in
something like that? 15 degrees doesn’t seem like much and is probably
worth the trade off. Ii thought it would be much more than that.

Joe Rivera

Spragless converters have their place as do ones with sprags or one way over
running clutches. Yes, sprgless do make more heat and under sum condition
will slow down the MPH. If your car makes in excess of 1200 ft lbs of torque
most sprags will slip. If the car weighs over 3500 lbs with 3000 + HP and
performs 6.17 in the quarter on ten wides and wins every event posssible using a
sprag type converter and running cool for 2 years every week end, I guess you
cannot argue with that. It all depends on applications and the lubricant.,

Dennis Sneath, Midwest Converters Inc / Midco Lubrricants.

Dennis what is the Best Lubricant you have found? We have tried many different types and have found the Mobil 1 synthetic to best of off the shelf stuff, Redline was pretty good in our endurance stuff also. I have one customer that runs Swepco and I have not seen a difference in the converter but he says he sees a big difference in the gear train.

All other synthetics and crude oils we have tried have just “skunked” on us when the above have worked.

Curious what works for others.

Dean Kuhn

Hello Rob,
Sprag type converters vs. spragless type converters has been a highly debated subject since it’s development in the early 1980’s, and will not be answered in one or two sentences. The fact that GM put a sprag in an OEM converter back in 1967 and before has confused many builders for the last 25 years.Transmission Specialties invented and patent the original designed spragless converter,After the patent expired many torque converter companies now offer a spragless torque converter for good reason ,They work! What we need to remember what the torque converter goes thru in a race car…

A converter sprag was designed for an OEM type vehicle
With advent of automatic transmission in the 1960s, it was necessary to engineer a converter with a sprag to increase gas mileage,reduce heat,and keep the converter from”loading”the engine at low RPMs.Inevitably, OEM converter builders were asked to build a high performance converter and they simply kept the sprag in the racing converter. These sprags were designed for OEM converters not for Drag Racing. Some OEM sprags have a maximum rating of 685 ft/lbs of torque and the best racing sprags manufactured today have a maximum rating of 985 ft/lbs of torque.That is the equivalent of 700-1100 HP. Even at these maximum ratings,NO sprag is designed to withstand the lock and unlocking that occurs during tire shake.
The first symptom of sprag problems is the intermittent sprag slippage.This occurs when the sprag locks and unlocks repeatedly causing internal skidding or chattering.This is the most frustrating symptom of a failing sprag as it will affect vehicle reaction time and will often do it on an inconsistent basis.Intermittent sprag slippage is the #1 cause of unexplainable reaction time loss or E.T loss in a race car. Most racers know,these are subtle changes that are not easily detected.Unless the racer is familiar with intermittent sprag slippage,They normally blame the track,the weather,bad button or all the other factors that make drag racing so difficult.Unfortunately,sprag slippage can go on for months before total sprag failure occurs

I hope this small bit of information helps in your search for information.

Ken Kelly