360 thrust bearing failing at 1000 miles

[mjdriver]

Hi guys i started hearing a weird noise the other day from my bellhousing area, turns out the ring gear was contacting the starter pinion. Inspected crank end play, found around 14 thousandths play, spec is 8 on the loose ends. Pulled the pan and found the thrust bearing worn on the trans side, 5 thousandths less material on that side than the front side. Engine was rebuilt 1000 miles ago,new pistons and rods, crank ground 010. Undersize. Trans is a th400 rebuilt at the same time with b&m shift kit and Hueghs performance converter. I installed the converter per the instructions and has the proper air gap before seating it, as well as the ring installed in the crank. Both engine and trans built by reputable shops. Installed by me. Engine builder is blaming the converter. What do you guys think?

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[fulsizjeep]

I wonder if the collar/shim is installed in the back end of the crank shaft where the torque converter snout fits in it.

See "sizing ring" here:
https://www.novak-adapt.com/catalog/pil ... /j5352374/

[mjdriver]

I wonder if the collar/shim is installed in the back end of the crank shaft where the torque converter snout fits in it.

See "sizing ring" here:
https://www.novak-adapt.com/catalog/pil ... /j5352374/

Yes sir it is, I bought it from Novak.

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[Dr.Bob]

A ballooning converter is about the only thing that would cause that kind of damage in such a short amount of time.

[mjdriver]

A ballooning converter is about the only thing that would cause that kind of damage in such a short amount of time.

That's what the owner of the machine shop told me, I haven't got in touch with the transmission shop yet, I think I'll get it going again and mabey run it by them, I'm thinking possibly excessive line pressure.

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[Dr.Bob]

Even if you had excessive line-pressure, it shouldn't be pushing the converter forward enough to damage the thrust-bearing in that short a time, without there also being other radical problems, like harsh shifts and such. But, you never know.

[mjdriver]

Even if you had excessive line-pressure, it shouldn't be pushing the converter forward enough to damage the thrust-bearing in that short a time, without there also being other radical problems, like harsh shifts and such. But, you never know.

The shifts don't feel excessively hard, I don't have any experience with the th400 so it's kinda hard to judge. Shifts are pretty smooth unless you get on it hard then they harden up. Only thing I wasn't that happy about was the shifts are pretty early, especially 2nd if your driving easy. I don't know if the B&M shift kit could have something to do with it, I told them to install it as the "RV" type set up. Maybe I should go back to stock if possible.

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[sansabarJ]

Ok , this I've seen before with a turbo 400 . Yes it can happen in 20 miles , let alone 1000.miles.
The problem IS torque converter pressure is forcing your crank against the thrust bearing surface.
I would recommend to take that converter out and install a stock original use convertor.
A test is to install a oil pressure gauge into your output trans cooler line . This test will show you the oil pressure in the line . This directly relates to the torque convertor pressure . You'll likely find from 30 psi in gear at idle to 80 psi driving and gauge can peg under acceleration . It's a serious issue and a turbo 400 problem due to its design . Hopefully your crankshaft thrust surface is not damaged . Remember that sheared bearing material has went thru your engine . A bummer situation that must be addressed . I know this problem very well and even your transmission tech will deny it's a problem . Another issue is to make certain your trans cooler is replaced to ensure no restriction which also cause this exact problem . Restriction equals high line pressure in the cooler line . I've seen this issue with the turbo 400 in pickups where an RV or a diesel convertor was used and not the proper stock torque convertor . A gauge install in Any event will give you piece of mind once your truck is back together . Average line pressure driving or accelerating will be right about 30 35 psi maximum . Take heed , get that convertor removed .

[sansabarJ]

Oh as an aside on early shifts , adjust your vacuum modulator . A tiny flat blade screw driver fits into the vacuum hose tube on the modulator. Turn clockwise to give later upshifts . Make about 1 to 2 turns and drive it . See how it then shifts . The turbo 400 transmissions are great heavy duty units . The hard shifting however will not cause a engine bearing problem . Might get annoying is all to the operator .

[sansabarJ]

I'm sorry , I did not address the shifts being harsh or not . The shift kits and subsequent valve body modifications provide hard manual shifts ( drag racing using your shifter to change gears )
The shifts results you are experiencing in the turbo 400 is to be expected . Harder acceleration off the line may or may not produce a hard shift in automatic mode . You really do not want a harsh aggressive shift , only a nice firm shift . Turbo 400 tranny are built for heavy duty use and provide just that .

[mjdriver]

Ok , this I've seen before with a turbo 400 . Yes it can happen in 20 miles , let alone 1000.miles.
The problem IS torque converter pressure is forcing your crank against the thrust bearing surface.
I would recommend to take that converter out and install a stock original use convertor.
A test is to install a oil pressure gauge into your output trans cooler line . This test will show you the oil pressure in the line . This directly relates to the torque convertor pressure . You'll likely find from 30 psi in gear at idle to 80 psi driving and gauge can peg under acceleration . It's a serious issue and a turbo 400 problem due to its design . Hopefully your crankshaft thrust surface is not damaged . Remember that sheared bearing material has went thru your engine . A bummer situation that must be addressed . I know this problem very well and even your transmission tech will deny it's a problem . Another issue is to make certain your trans cooler is replaced to ensure no restriction which also cause this exact problem . Restriction equals high line pressure in the cooler line . I've seen this issue with the turbo 400 in pickups where an RV or a diesel convertor was used and not the proper stock torque convertor . A gauge install in Any event will give you piece of mind once your truck is back together . Average line pressure driving or accelerating will be right about 30 35 psi maximum . Take heed , get that convertor removed .

Hmm, I have an eBay aluminum radiator and a "summit" brand heat sink style cooler, the cooler is plumbed in series with the radiators heat exchanger, I'm thinking it may be too much restriction having two coolers plumbed together? Really wishing I had a manual trans at this point...

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[sansabarJ]

What I found in my 45 years of mechanics work is trans coolers get restricted if you have some transmission failure as debris plugs the cooler . I once had a customer with a 72 Chevy truck with a 350 and turbo 400 trans using an old Freon refrigerator cooler for his tranny cooler .
While it might seem it can work at first glance ,it caused the exact restriction I've discussed and wiped out his crankshaft thrust including the crank itself . I'm sure your new cooler and radiator cooler are fine.
They are designed for proper flow . It's a common recommended setup to have the radiator cooler flow into the trans cooler and back to the transmission . But yeah a 4 speed or 5 would be a nice thing , shifting gets old though . As stressful as this is , I bet your old trans and engine had no thrust bearing destruction . Do not let the cooler restriction problem cause you stress.
My 400 and 360 are totally fine and no issues as most all are . You got bit by somthing most have no idea can occur in a turbo 400 transmission.

[letank]

Hmm, I have an eBay aluminum radiator and a "summit" brand heat sink style cooler, the cooler is plumbed in series with the radiators heat exchanger, I'm thinking it may be too much restriction having two coolers plumbed together? Really wishing I had a manual trans at this point...

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Most of us have the dual cooler set up, radiator and external cooler. my 74 has about 350K on original TH400 trans, owned since 1983... but parked for the last 3 years until I deal with the rust. It still shifts fine.

Thank you sansabarj for the tips on the modulator adjustment

[SJTD]

So why do they sell this torque converter if it kills thrust bearings? Or why is mj"s the only one? What vehicle does it work ok in?

[mjdriver]

Hmm, I have an eBay aluminum radiator and a "summit" brand heat sink style cooler, the cooler is plumbed in series with the radiators heat exchanger, I'm thinking it may be too much restriction having two coolers plumbed together? Really wishing I had a manual trans at this point...

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Most of us have the dual cooler set up, radiator and external cooler. my 74 has about 350K on original TH400 trans, owned since 1983... but parked for the last 3 years until I deal with the rust. It still shifts fine.

Thank you sansabarj for the tips on the modulator adjustment

Good to hear I didn't mess up the cooler setup

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[mjdriver]

So why do they sell this torque converter if it kills thrust bearings? Or why is mj"s the only one? What vehicle does it work ok in?

This is what's bugging me, swapping to a higher stall converter is nothing new, and it's not like some no- name brand. I did install spacers between the converter and the flex plate, according to my measurements there was too much space between the two, I'm going to double check once the new bearing is in.

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[Stuka]

So why do they sell this torque converter if it kills thrust bearings? Or why is mj"s the only one? What vehicle does it work ok in?

It most likely has multiple applications. Not all V8's are as picky with thrust pressures as AMCs are.

[sansabarJ]

I have seen 5 or 6 turbo 400 torque converter thrust fails . It's not somthing that happens only to AMC as I pointed out with the 72 Chevy C20 . But it does happen . I had a Chevy C30 with a 350 and a turbo 400 . Heavy duty torque converter ,nothing race and no high stall . In 50 miles the crank thrust surface and of course the bearing were destroyed., oil pressure went from 40 psi to 10 psi at idle . Its this internal pressure was TOO HIGH . You need to look at how the hydraulic circuits direct ATF flow in a turbo 400 and this really helps to see what is going on . Early Buick 400s with the switch pitch convertor did not do this. The front pump has a pressure relief valve in that transmission . All other 400s do not . There is no way to bleed off the pressure as is normal in other transmissions . I.E. Turbo 350 700r4. 4l60E Torqueflites and so on . The transmission coolers , if they have , or give any restriction to fluid flow can cause this same problem to be sure .
Install a pressure gauge in your trans cooler line is the surest way to know if your issue is solved
Read the pressure " BEFORE " fluid enters the transmission cooler/ coolers. Think of a manual trans in our trucks or any vehical for that matter , and the pressure the thrust bearing has on it when you have your clutch pedal pressed down at a stop light for example.
No unusual abnormal thrust wear normally occurs in this situation . There is however. High thrust bearing loading going on as the crank /clutch flywheel assembly is forced forward on the thrust surfaces . In my hotrod days of high stall race convertor uses , never had a thrust issue, but we had converter issues off and on . A word of caution is to remember higher stall speed converters produce more heat in the ATF fluid by nature of how they SLIP to create the higher stall. Have a very good cooler installed to. Keep things cool . Hope the thrust bearing replacement goes well .

[mjdriver]

I have seen 5 or 6 turbo 400 torque converter thrust fails . It's not somthing that happens only to AMC as I pointed out with the 72 Chevy C20 . But it does happen . I had a Chevy C30 with a 350 and a turbo 400 . Heavy duty torque converter ,nothing race and no high stall . In 50 miles the crank thrust surface and of course the bearing were destroyed., oil pressure went from 40 psi to 10 psi at idle . Its this internal pressure was TOO HIGH . You need to look at how the hydraulic circuits direct ATF flow in a turbo 400 and this really helps to see what is going on . Early Buick 400s with the switch pitch convertor did not do this. The front pump has a pressure relief valve in that transmission . All other 400s do not . There is no way to bleed off the pressure as is normal in other transmissions . I.E. Turbo 350 700r4. 4l60E Torqueflites and so on . The transmission coolers , if they have , or give any restriction to fluid flow can cause this same problem to be sure .
Install a pressure gauge in your trans cooler line is the surest way to know if your issue is solved
Read the pressure " BEFORE " fluid enters the transmission cooler/ coolers. Think of a manual trans in our trucks or any vehical for that matter , and the pressure the thrust bearing has on it when you have your clutch pedal pressed down at a stop light for example.
No unusual abnormal thrust wear normally occurs in this situation . There is however. High thrust bearing loading going on as the crank /clutch flywheel assembly is forced forward on the thrust surfaces . In my hotrod days of high stall race convertor uses , never had a thrust issue, but we had converter issues off and on . A word of caution is to remember higher stall speed converters produce more heat in the ATF fluid by nature of how they SLIP to create the higher stall. Have a very good cooler installed to. Keep things cool . Hope the thrust bearing replacement goes well .

Thanks for the info, one question I have is which cooler line is the outlet, and which is the return? Bearing replacement went ok , crank thrust is back to .003" , still need to re install the pan. So I removed the converter bolts and spacers, I have about 1/4" of gap between the converter and flexplate, should I use any shim/washer, or just bolt it up?

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[sansabarJ]

The correct convertor gap is about 1/4 maximum and no more " . You do not need it tightly shimmed , as it needs clearance . The convertor will slide forward into crank hub upon bolting it up to the flexplate . So yes that is normal and you want that clearance . A flexplate does just that it flexes as the convertor moves forward and back under operation . You do not want it tightly shimmed up.
The lower cooling line on the case is the pressure out . Upper fitting is your return .So check that pressure before any testing it out on the road though . Thrust on crank is good . Happy you had no crank damage .