Thrust problems with two step in Stock

[GTX JOHN]

My son and I have both have lost thrusts on our Stocker
that run two steps.

Our SS cars have never lost the thrust. Many of our engines
have the same crankshaft builder.

Is there something about how the works on a brake petal
that is different than the way it effects the engine on a brake.

That does not make any sense to me, that there would be any difference
as both ways they operate under similar load.

It seems to happen about the 100 to 125 run point on the stockers.

Do I need to find a new crank man, I have been using the same guy
for last 30 to 40 years?

Does anyone else have this issue?

Appreciate any Feedback!

[1legjerry]

Have you checked your tranmission pump pressure?

[GTX JOHN]

We will check that.
Thanks!

All our transmissions for 30 years have been bought
from our friends at Pro Trans. (Waco, Texas). We seldom
(Maybe Never) have had and issue with them.

However, anything is possible.

[Tom Goldman]

Pump pressure is usually the number one culprit .
also check to make sure the converter pilot is not bottomed in the crank .
I've seen that problem on several SCAT small block Mopar cranks that caused thrust issues.

[GTX JOHN]

What should line pressure be?

110 PSI?

Just guessing as I have not done my own transmission
for 30+ years.

[Henrys Toy]

Originally Posted by GTX JOHN

What should line pressure be?

110 PSI?

Good morning John and to all,
Now what I'm about to say is not a recommendation for the line pressure in your transmission. In the past I ran 165 to 175 line pressure in my Glides and it didn't smear the frictions, and they lived a long life without thrust bearing problems. More recently I'm running 180 lbs. in my metrics, without smearing the frictions or any thrust bearing problems. I've known some racers to have less line pressure and a few to have more, what I'll say is - what line pressure works for you without destroying parts is best.
My past experience tells me that torque converters and/or front pump clearance's will more than likely be the root cause. If the thrust bearing is worn excessively on the converter side that would be my first clue as to where to look next. I'm going to say - if the gentleman that's been doing your cranks for you all these years without failure , and you've recently started having problems in that area , then he's not the problem.
Have a good day.

Respectfully,
Henry Kunz 1534 H/SA

[Steve Stasko]

Originally Posted by Henrys Toy

Good morning John and to all,
Now what I'm about to say is not a recommendation for the line pressure in your transmission. In the past I ran 165 to 175 line pressure in my Glides and it didn't smear the frictions, and they lived a long life without thrust bearing problems. More recently I'm running 180 lbs. in my metrics, without smearing the frictions or any thrust bearing problems. I've known some racers to have less line pressure and a few to have more, what I'll say is - what line pressure works for you without destroying parts is best.

While the info you provided is good, I don't know if a Torqueflite can be compared to a Glide or TH. I've never run more than 140 psi in a 'footbrake' 727. A transbrake 727 usually needs 150+ depending on who's brake is being used...then I've heard of people running as much as 200-220 with a brake. I was always under the belief that you should run as little line pressure as you can get away with.

[GTX JOHN]

Thank you Gentleman for the replies.
I appreciate the help

We removed and welded up the crank in the
Superstock which is cast to get through the year

I have been told that the welded thrust will not hold up
very well. Not by the place that did it. However, told that
by my regular crankshaft guy (Castillo) who would not touch it.

I am debating running on a foot brake rather than using any
starting line two step at all.

[Cglrcng]

Originally Posted by GTX JOHN

Thank you Gentleman for the replies.
I appreciate the help

We removed and welded up the crank in the
Superstock which is cast to get through the year

I have been told that the welded thrust will not hold up
very well. Not by the place that did it. However, told that
by my regular crankshaft guy (Castillo) who would not touch it.

I am debating running on a foot brake rather than using any
starting line two step at all.

John, I am no expert on a 2 step by any means as have always so far been a foot brakes. But I watch a whole lot of no prep and drag and drive action on super prepped tracks also and though most of them use a trans-brake they also are almost all boosted applications and use the cut of spark or fuel and many, many...beyond belief also suffer damage from loss of crankshaft thrust bearings.

Logic just tells me that the constant pressure of coming up smoothly against the crank at a constant rpm and Trans pressure has to be kinder on forward thrust and pressure on that crank and thrust bearing, than any jack hammer type action no matter what you do using either spark or fuel cut in a T.B. or a 2 step (no matter how they may brand it as soft touch).

Many engine builders (including Steve Morris on his own and Cleetus McFarland's high dollar superb built SMX which are a fast fortune each), in the no prep world in the last few years have gone on to devise and install special bearings that we cannot add that are added to the front of the crank between the block and the timing chain covers to combat just the issue that you are seeing.

And some of them have been successful so far, many of them have yet to get enough passes on the redesigned engines yet to make a clear judgment and as said much has been blamed on and worked on transmission pressures to lessen the push pressure which is all forward, never the opposite.

I can also say that at 93K miles on my little always foot braked 4 banger of an engine, every bearing both rod and crank showed no wear whatsoever except the thrust bearing shells. And only on the outsides (no crank damage).

I have seen no prep boosted guys tear up a lot of cranks and even split and blow up the timing chain/belt covers. So we need to take a hint from the extremists that when they are popping and banging away up on the Rev limiter they have to be jack hammering that crank a bunch with on/off forward thrust. They do not have as many passes as very few do much qualifying just some testing.

It is not the old days...Newer tech always brings newer issues. It just takes a while to take its toll. Some of those guys are tearing their freshly rebuilt stuff up really fast, so rolling out and back in a new thrust bearing at maybe 75 passes to 100 might just be the new preventative maint. to avert damage.

[Cglrcng]

Lots though have looked at it from a Trans pressure perspective too, and have applied a ton of attempted fixes, bypasses, and tricks to reduce the pressure on the hit. I have not seen much so far that solves the issue as it seems like a band-aid IMHO, then it rears its head again later.

We all just wanna go faster and faster. Even us really slow guys. Here I sit doing my Holley ECU wiring diagram and deciding on my future 2 step install.

And second guessing. (Who am I kidding, I don't make enough horsepower to tear anything up!) Or do I?