habfan

Hi, my first post:

I have a problem; it is a 350 tpi chev with a 350 turbo tran and it is in a 1947 ford coupe, something is taking out the thrust bearing in the engine. It has happen 3 times, on two different blocks.

I had the engine rebuilt at a reliable place. Before I install it again, I would like your opinions about what it might be. This is what has been done so far:

The car has been set up properly at a local hotrod shop for the engine and tran setup.

Your normal rebuilt 350 with vortec heads and comp 256 cam.

Transmission and torque converter has been tested and they say everything is okay.

Any ideas will be appreciated.

Les

sofakingdom

iTrader: (1)

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habfan

2 times on one block, third time on different one

Thanks

Les H

dimented24x7

iTrader: (2)

I assume it was the same trans being used and the side of the bearing facing the trans each time?

Ive heard of thrust bearings being taken out due to excessive pressure or restrictions in the front pump that, due to too much pressure, force the torque converter out, and overload the thrust bearings, destroying them.

habfan

yes, it is with the same trans and it is pushing the crank forward from the trans. The shop were I had the engine built, that I will be putting in, also went through the trans and torque converter, said nothings wrong. any other ideas?

I am thinking that I might replace the trans and converter. Don't want to pull the engine out again.

Thanks

Les

hartman

iTrader: (6)

is it a stock torque converter? or stall? From what ive seen/heard stall converters are the number one cause for thrust bearing failure.

dimented24x7

iTrader: (2)

What kind of line pressure are you seeing in the trans? Can the torque converter be slid back away from the flexplate with the trans installed and TC not bolted up? Its possible that the trans is technically OK, but the load from the converter being too much to bear for the thrust bearing. They can only take a couple hundred pounds or so, much less than the main and rod bearings. If your running too much line pressure, or the FP has a restriction, it will eat the thrust bearing. I did a quick search and heres an example of a trans with a restriction in the FP: http://www.youtube.com/watch?v=YEfqKoilLkI

Also, what kind of bearings where you using? Standard tri-metal lead/copper?

habfan

Thanks for the replies,

It is a 2000 stall

Talked to the engine/trans builder, they are leaning to the tc for the problem. the internals of the trans shows no sign of moving forward.

We will check the pressure in the trans cooler lines.

We will bolt up the engine and trans with the old tc (should be about 1/8" of space between the tc and flexplate?)while it is out of the car. Then replace the tc with a new one, to be on the safe side, maybe trans too.

It will be a couple of weeks before we can work on the car. I will let you know how things turn out.

Thanks again for the replies,

Les

david chambers

sometimes,the trans bell housing wont be "square" you cant tell it by looking use a dial indicator to check.

1969RSSS

Torque Converter moving forward or swelling is the #1 cause of thrust bearing failures in automatic transmission vehicles.

habfan

Hi again, we had some health problems.

Start working on the car again. Engine and tranny is still out of car, we put it together and there is between 1/8 to 1/4' of movement between the TQ and the flex plate (before it is bolted). Will the TQ balloon that much?

sofakingdom

iTrader: (1)

No. That's normal. The flex plate tends to pull the pilot on the front of the TC up into the large part of the crank pilot; the TC is designed NOT to sit all the way up into the trans. In normal operation, everything should have clearance in there.

In fact, that ¼" or whatever of gap in there, is how much the converter would have to "balloon" to cause this, and is designed to be like that SPECIFICALLY to prevent this failure mode. Which is very rare indeed, unless the converter is inherently fornicated somehow.



That disc that's about 1½" dia on the front of the TC is the pilot; the crank part of the pilot setup for an auto trans is the tall ridge around the little hole for the pilot bearing for a manual trans that this crank has installed in it.

habfan

Thanks sofakingdom,

Next questions, can tran fluid pressure move the TQ due to plugged tran line to cooler (have not checked yet) or if a shift kit is not installed right, would it build enough pressure to move TQ.

Thanks,

Les H

sofakingdom

iTrader: (1)

Something along those lines CAN happen; not sure of the details though.

OTOH, to be enough pressure to be more than, for example, the draw pressure of a manual transmission clutch (3000 lbs ± 1000 lbs or so) it would have to be AHELLUVALOT of pressure, since it would be acting only on the hub, which is not many sq in, so to get lots of lbs of thrust, you'd need LOTS of lbs per sq in.

Frankly, I have NEVER in all my days, seen a thrust bearing wiped out for that cause. Now granted, I've only been in this hobby for 30 some-odd years now, and have only worked on a few hundred cars, and I still learn new stuff EVERY DAY, I freely admit I don't "know" "everything" there is to know about them; but still, I'd be looking real carefully for alternatives before I just jumped to that conclusion, all the same.

First thing I'd be looking at, personally, would be the crank; especially if the same one was involved in all of the failures.

The thing about the BH not being square is a potential issue as well, although the actual most common issue there is, the BH dowel pin holes are not centered on the crank CL. It's a block machining QC problem, very common in 70s blocks, almost as common as The Starter Bolt Hole Problem and The Lifter Bore Problem. I have a 454 that has that, can't keep a Turbo 400 for more than a few thousand miles in that car, next time I'll probably finally get motivated and put in some offset dowel pins such as these http://www.summitracing.com/parts/LAK-15930/. But that more usually eats pump bushings (what my 454 does), not thrust bearings.

habfan

Thanks,

Dad has been a mechanic for 55+ years and he never had a thrust bearing failure due to automatic trans.

It was 3 different cranks, the new crank is a scat.

The tranny came from a 77 nova that we owned. It had about 230,000km on it with no problem before. We had it rebuilt and a shift kit installed.We just want to cover all the bases before we install it again. I did order another TC.

This has been a 11 year father and son project.

Thanks for the help,

Les H

Damon

I think I'm with Sofa on this one, to a point. I've heard of auto transmissions chewing up thrust bearings, and I believe they do if pressure in the converter is high enough. I just haven't run into that problem myself. Likewise, I've been around the hobby for a little while (about 25 years). And likewise, maybe I've just been the lucky one all these years.

Now with a bad converter, sure, I can see a problem. A trans that isn't square or concentric with the crank, OK, I can buy that, too.

But my first go-to suspect would be the crank. A crank that's wiped a thrust bearing once is instantly drawing my attention. It's difficult to machine the thrust surface and make it work again if it's even marginally chewed up. Even if you can, there is a very limited selection of rear main bearings that have extra "beef" to make up for the metal lost to remachining the thrust surface (typically only a couple thousands of an inch over stock). How's crank endplay with new bearings installed?

After that would be a balooned converter, but with the clearance you describe, that can't be it.

So I guess I'm back to the crank if it's not a bad converter or crooked parts.

dimented24x7

iTrader: (2)

I had my original auto fail twice due to misalignment. It will show up real quick in the front pump. The bushing will wipe, and the rotor will chew into the front pump covers when the TC is forced to turn at an angle. If its bad enough, you can also see where the bolts eat into the flexplate, as they move around when the misalignment is real bad.

habfan

We checked the trans. lines and there was no blockage, same with the cooler. With the TC having 7/64th" clearence, we decided to go with a new tranny (T350 B&M) to go along with the new TC.

We are planning to install this weekend.

Thanks for all the help, we will let you know how it turns out.

Les H

habfan

Thanks for all the information. The cars is up and running, everything is fine so far.


Les H