Don Terrill’s Speed-Talk

Hey guys
Looking for something that would point to a worn thrust on a sm jorunal 327.
This was a resto job months ago and when it was 1st here it had a smoked thrust like someone road the clutch all its life.
Now I find out its a power glide trans and they do not usually do this.

Anyone have any ideas where to look in the trans. There was lots of clearance between the flexplate and the converter and the pilot was no bound up in anyway.
The complaint was a slight knock going up hill from a stop which is the reason its back but now I see the thrust done not sure which direction to go in now with the trans.
Suggestions welcome
Dave

I don't see how it could be the trans if the converter nose is definitely not binding or bottoming in the crank.
My guess would be an installation tolerance problem with the thrust bearing during the reconditioning.
Someone may have failed to check the crank end float, and it may have been assembled pretty tight.

Look for a slightly tweaked rod. It will impart an axial thrust.

Warpspeed wrote:I don't see how it could be the trans if the converter nose is definitely not binding or bottoming in the crank.
My guess would be an installation tolerance problem with the thrust bearing during the reconditioning.
Someone may have failed to check the crank end float, and it may have been assembled pretty tight.

Block was bored square and crank is square in block. End play was .006 when fresh.
The thrust faces of rear cap were cut 90deg to centerline and turned free when originally built. The thrust bearing was coated and checked for square contact as well.
Crank was badly worn tto start with like a clutch pedal rider drove it. This guy is also a DIYer and has been in the trans since it was built so there may be an issue internally. Trans has gone back to shop that built it for a check up after finding it has had the VB apart.

Kevin Johnson wrote:Look for a slightly tweaked rod. It will impart an axial thrust.

Rods were checked for straight after resizing on TA machine as well as Sunnen rod aligner. There was 3 rods replaced during the build because they were twisted and bolt holes were stretched and would not hold a ARP bolt. The engine had been done at some point and the rods that were replaced had loc-tite holding the rod bolts in place.
New bolts would slide in with your finger pressure.

The one item that may have slipped by is the belhousing flange squareness to the crank.
Thats tonites mission to check the flywheel to block runout.

I have been told that too high of line pressure will force the converter forward and wear the thrust as well.
The trans guy is going to dyno the trans and see if there is an issue in that area.

thrust is wearing on the back side because the torq converter is ballooning i been threw this before many times

If it is the converter nose pressing into the crank, then there should be some wear or markings visible if it has been pushing hard enough to destroy the thrust bearing.

This does seem the most likely cause, as everything else has been pretty much eliminated.
If the whole thing has been running tight, chances are the oil pump in the trans will also show some damage.

cbeng wrote:thrust is wearing on the back side because the torq converter is ballooning i been threw this before many times

That will be seen when on the dyno I am sure but I did inquire about the converter and it is just a stock unit. I relize that it could be an issue but the guy that owns the car is like 85yrs old and never goes on the hiway so its not a hot rod deal just a plain resto deal as the old guy has had the car since new.The engine has been done several times in its life from complete rebuilds to re-ring jobs over the years.
When I got it it was re-rung and the tops of the bores were over 4.045 while the pistons were .030 and had been re-rung 3 times and rebored one time before I did it.
The block is .060 now fortunately is sonic tested thick enough as it was a numbers matching block but all that aside the trans was the original and has been redone and after a short time of running it wore out the thrust bearing before I seen it and the only thing thats common is after the trans was repaired both times the thrust bearings had an issue.

He only drives it to local shows and other gatherings so its not a daily driver but as mentioned after the trans has had work both times the thrust bearing gats worn out. Coinsidience??

If it hasn't been pulled yet check pressure before and after the cooler.
Had a local shop not believe that. The first two engines didn't make it off the lift. After the 3rd gratis NAPA rebuild he finally got to checking it. Shore nuff!. He didn't believe me the first time because a tranny shop told him that was impossible due to the pump relief in the tranny. Guess what? It can't dump off that much.

I went thru this a few years back when I put a 400 trans in my car.I changed everything in the motor including the block,crank,rods and pistins.When I checked the cooler line pressure,it was over 90 psi.It is supposed to be below 40psi. I put my 350 trans back in and never had a issue since.Get the cooler line pressure checked.

Thanks Dave
Thats my thought as well I have the rad out to the rad shop to check the cooler for flow and the trans is going on the dyno tomorrow and the line pressures will be tested as well as the cooler for blockage.
I have had the other trans guy tell me its impossible for it to be a trans issue but there have been tooooo many tech bulletins out over the years just for this same issue and a couple others where they are prone to thrusting the converter forward.
Hopefully the trans will show something as well as the cooler.

always putten in neutral at traffic lights ,then wen light turns green droppen in D

Take a real close look at the thrust surface of the crank. If it has ANY scratches that you can see on it, it needs to be polished. The scratches will come from the radius of the journal on run on an angle across the thrust surface (I hop this makes sense). Kind of a starburst pattern. This is cause by poor polishing and the side of the stone riding along the thrust surface when polished. This isn't something you can't fix in your shop. If you see any scratches even tiny ones, they need to come out. They act like a windshield wiper while the crank is turning and they wipe the oil from the thrust surface. I ran into this with an Eagle crank I have. I polished it with 1000 up to 2500 grit. Shines like chrome and haven't had a problem since. Good luck.

If the converter ballooned enough to wipe the thrust bearing, the trans pump will also show damage.

Excess converter pressure will cause the converter to slide forward on the splines, and can apply enough pressure to the thrust bearing to damage it. Primary cause here, as previously stated, is a restricted cooler circuit.

http://www.enginebuildermag.com/Article ... ilure.aspx

Schurkey wrote:If the converter ballooned enough to wipe the thrust bearing, the trans pump will also show damage.

Excess converter pressure will cause the converter to slide forward on the splines, and can apply enough pressure to the thrust bearing to damage it. Primary cause here, as previously stated, is a restricted cooler circuit.

http://www.enginebuildermag.com/Article ... ilure.aspx

Seen that article good info should be in other publuications.
I believe its the issue with the line pressure too high and forcing the converter forward as mentioned in the article.
The internal cooler in the rad was never replaced but the dyno results will tell the story tomorrow.

I will keep you all posted with pressure results from the test.
Dave