anybody know why a 727 would tear up the back of the thrust bearing!!??? don't think the coverter is balloning ??

Just the back.. the conv is balloning and pushing forward on
the crank

Line pressure possibly too high pushing the converter forward.

Most of these boil down to the pilot on the converter being bigger than the crank register.

Some more info would help. How much engine, what converter and what crank.

Kevin

Jim, was a cam button used? A cam, walking out the block could pull the crank with it.

When I got my short block (Mopar Mega block, 4.5 Mopar crank from Indy) it only had 18 passes on it since freshened. I tore it down anyway and found the thrust torn up. Crank even showed a little heat. After talking to the previous owner he said he had a converter issue. I polished the crank and put it back in. It had the tightest crank end play I've ever measured, .003". It's been in the car for 200 passes. Just pulled the pan to check the bearings. Thrust looks like it came out of the box. My bet is converter.
Doug

Who's converter?

its a ati convertor i have never had this problem before seemed to do it in one pass at the track on motor no no2 ?? same convertor and combo for 7 years i fresend the trans and motor 1 1/2 years ago rick it ahs a geardrive on it witha cam button all looked good there, i will send the covertor back ive had it for 10 yrs its a ATI blown fuel convertor and i will take the trans apart again to ck it thanks for all the in put

Being that its a older conv and has many cycles on it, its possible
that the walls of the conv are getting weaker from flexing and is
actually starting to flex more... just a guess
EDIT
Didnt you use spray on that engine in the past.. if you did you
might have stretched the front wall and it has less distance to
move when it heats up

its a 606 cuin hemi calles crank and a ati convertor like i said before its all been together since 2007 , never a problem ive ssen turbo 400s ruin crank thrust bearings from the covertor charge hole size on the pump puts pressure on the convertor never heard of this on a 727 anybody else ??

I've seen it on a Hemi my builder did. His customer swapped the 440 in his 70 RR for the Hemi and used the trans and converter that was in the car. It wiped out the thrust on the Hemi in short order. The 440 thrust was OK.

The Hemi was built with the stock crank and just basically warmed up a little.

According to my trans shop you can run a Hemi core converter behind a wedge but you can't run a wedge converter core behind a Hemi. He said the register sizes are different. Hemi is smaller.

I have never measured to confirm this.

In any case a new converter and thrust bearing in the Hemi and all is well.

Kevin

I've seen 3 where the thrust was wiped out on the rear.. all
3 were from the conv expanding... and I have heard of more
but I only seen the 3
EDIT
All 3 I seen were 727

gonna send the convertor back to ATI this week ill ck it in the back of the crank 1st, im gonna pull the trans out and check the end play and pull the pump out of it take a peek before putting it behind the new bullet , thanks for all replies , gonna call john at CRT also pick his brain !!! since all the trans parts are from him !!!!

I was thinking about this last night... when you get a new
conv you might want to measure the thickness of the conv so
you have a reference later on... granted I have never done
it but maybe we all should

If you can't seem to find anything wrong and certain the converter is not ballooning, add oil groves to that main. I had the same issue of wiping the thrust and couldn't find any evidence of the converter and was advised to add groves for extra oiling from my transmission builder who builds/races sprint cars. Have not had a problem since.

When you mated the trans to the motor did you check the end play of the converter between the flex plate and the aft most position of the vert before you bolted it to the flexplate? I have read that 0.125 gap is good. My latest build has about 0.100.

can you explain more on grooving.

I didn't actually to the work to the bearing, but my understanding is that he added an extra grove to the thrust side of the bearing face to allow for better oiling. From what the tranny builder said, Fords are bad about wiping out the thrust due to poor oiling.

An automatic trans is ALWAYS trying to push the converter out the front, when the line pressure gets up, that's just a fact. Now, if you are pushing more fluid in the converter than it can exhaust, it will burn the thrust out of the motor. So what can cause that? If the converter has a sprag, it could be going out. Otherwise something in the trans is not allowing the converter to exhaust fluid properly.

Guys talk about "ballooning" all the time. You would need virtually zero snout clearance and an incredible amount of core expansion for that to actually hurt a thrust. Its normally always a fluid issue

Monte

Doesn't it go from converter to cooler? ie; cooler's plugged? I always wondered what the symptons of a pinched line would be.

Jim we had a similar problem and after following a lot of the aforementioned causes we found the converter snout and crank register was not fitting correctly.It was only after we trued up these two mating surfaces did we eliminiated the problem.For what it's worth it was a 605" hemi with Callies crank and ATI converter.There was a flat ridge on the converter snout and the witness marks on that area and in the crank showed it was tight on a small area.After truing up the snout on the lathe cleaning up the crank register we never had the issue again.

Dealing with this issue in my cousin's 67 Firebird with a stroker 400. It now has wiped the thrust bearing twice. First time blamed the pressure in the tranny as the tranny had been rebuilt. This was a new build with the new stroker crank - old stock crank was fine.

In 125 street miles lost 0.010 inches in the thrust with the rebuilt motor. We are trying to cover all bases this time.

We want to know for sure if the tranny is causing excessive thrust on the crank so I believe we will measure the thrust force on the crank before we tear it apart. We have a plan...........

mark i know for a fact that a turbo 400 will wipe out the thrust bearing in the engine it is behind, if the convertor charger hole in the pump is not taken car of go to yellow bullet hutch trans section !!!!!

thanks for the input BOB i will check that before i reinstall it i sent it back to ati it hasn't been freshened since 2008 [i found paper work on it] cant hut to have it checked ?? its just weird that it happend so fast ?? one pass NO NO2 !! i noticed it lost about 20 psi of oil pressure so i put it on the trailer, took it apart 2 days later and i found metal in the oil pan only thing wrong was the back of the thrust bearing was destroyed all the other bearings were near perfect

Same crank, same trans, same converter that you have ALWAYS run, with no issues. So look at it logically. Did the converter to crank hub fitment suddenly change? Highly unlikely.......So what else was changed? You freshened motor and trans. So looking at it from that standpoint, you either set the thrust up WAY tight or something in the trans is not letting the converter exhaust the fluid fast enough............Or, like I said, the element in converter COULD be going away, but I am still betting something in trans. Ten year old converter though, so it sure wouldn't hurt to have it looked at and freshened

Monte

yeah , monte im going to take the trans a apart , check my trans cooler and lines and i sent the convertor back to ati , i checked my my records the thrust was .006 , ill post back what i find !!!!

Thanks! I did not know Yellow Bullet had a tranny forum. Did find some interesting info.