Re-using Torque converters

JayArr

Original poster
Member
Sep 24, 2018
531
Mission BC Canada
So I've got my transmission rebuilt and nothing in it actually failed. It was removed at high mileage but was completely operational when pulled. No filings in the pan or fluid.

So I want to avoid spending $430Cdn on a rebuilt torque converter by cleaning and reusing the one that came out with it.

When I read my old 1980 factory GM manual for my Olds 350 it says if there is no filings then just clean and replace the TC:

Converter Replacement
A converter should be replaced only if one of the following conditions exist:

1. The front oil cover or body are badly scored.
This results in having cast iron grindings entering the
converter and the oil circuit.
2. "Aluminized" oil in the converter. This comes as a
result of internal converter failure.
3. End play in the converter exceeds .05OW.
4. External leaks
5. A scored or damaged hub which could cause front
seal failure or front pump bushing failure.
6. A broken, damaged or bad fitting converter
crankshaft pilot.
7. The converter is off balance which results in a
vibration that cannot be corrected.

A converter should not be replaced for any of the
following conditions:

1. The oil has an odor, is discolored and there is no
evidence of metal particles.
2. The oil cooler was defective, allowing engine coolant
to enter the transmission. To correct this, refer to converter
flushing procedure in this section.
3. A small amount of wear appears on the hub where
the oil pump drive gear locates. A certain amount of such
wear is normal for both the hub and oil pump gear.
4. The threads in one or more of the three converter
bolt holes are damaged. Correct such conditions with the
use of a Heli-coil or its equivalent.

The manual then goes onto detail how to drill a 1/8" hole and flush the TC and then seal it back up with a closed end pop rivet.

I can go one step further since I have a mig welder.

Has anyone done this? drill a hole, flush it out and then just weld the hole back up?
 

JayArr

Original poster
Member
Sep 24, 2018
531
Mission BC Canada
Scratch the welding part...

A little google searching revealed that the preferred way is to thread and insert a 1/8" grub screw with permatex. That way you can drain again in the future if you want.
 
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Mooseman

Moderator
Dec 4, 2011
25,487
Ottawa, ON
I dunno. I wouldn't reuse the TC, especially if it's a high mileage unit. It would be like reinstalling your summer tires on your rims that just still have a little thread left but are still legal. Not the safest, won't last long and you'll have to pay again to have them dismounted to mount new ones. Or putting an old oil pump in a freshly rebuilt engine.

The clutch inside does wear out. Those manuals are made more for those just needing to send it as quickly and cheaply as possible (think dealers on warranty work).
 

JayArr

Original poster
Member
Sep 24, 2018
531
Mission BC Canada
Have you ever actually had the lockup clutch in a TC wear out?

It only engages in 3 and 4 on the highway so the symptom would be that the lockup engages but then slips. How would that be any different than if it wasn't engaged? Basically you told it to lock up but it didn't. I suppose it's possible but I've never heard of it happening before.

Even if the clutch completely wore out - the TC would still operate in all four gears, it just wouldn't lock up on the highway. It's not going to affect the rest of the car in any way, it's not going to wear out any further and it's not in any way unsafe.

Wouldn't loss of the TC clutch represent only a loss of fuel economy?
 
Dec 5, 2011
577
Central Pennsylvania
Have you ever actually had the lockup clutch in a TC wear out?

It only engages in 3 and 4 on the highway so the symptom would be that the lockup engages but then slips. How would that be any different than if it wasn't engaged? Basically you told it to lock up but it didn't. I suppose it's possible but I've never heard of it happening before.

Even if the clutch completely wore out - the TC would still operate in all four gears, it just wouldn't lock up on the highway. It's not going to affect the rest of the car in any way, it's not going to wear out any further and it's not in any way unsafe.

Wouldn't loss of the TC clutch represent only a loss of fuel economy?
Addressing your specific question.... under the best circumstances, "probably". But what sort of debris will the clutch failure scatter throughout your transmission? No matter how you slice this problem, it's a gamble to reuse a torque converter. You've got a slush box with all brand new internals... the prudent thing is to replace the TC and flush the cooling circuit completely and adequately. Every deviation from best practices raises the chance of failure.
 
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Mooseman

Moderator
Dec 4, 2011
25,487
Ottawa, ON
Have you ever actually had the lockup clutch in a TC wear out?
No because I have had the TCC modified to always engage 100%. Did that on 3 of them, never failed the TCC. However my 02's tranny itself failed internally at 340k km.

Wouldn't loss of the TC clutch represent only a loss of fuel economy?

At that point, like brakes, would rub metal on metal and send that shrapnel through the tranny. Seen that happen A LOT on the 6L80 as well as burned up TCC due to excessive slip. That's why I turn off TCC slip and have it engage 100%. Also reduces heat in the fluid and wear on that valve. The 4L60 doesn't suffer from TCC failures as much however on a used one, like @TequilaWarrior mentioned, it's a gamble.
 

JayArr

Original poster
Member
Sep 24, 2018
531
Mission BC Canada
No because I have had the TCC modified to always engage 100%. Did that on 3 of them, never failed the TCC.

I read one manual on transmissions that said very emphatically that the frictions and discs were not wearing parts. That they weren't expected to wear and need replacement and that the only time that happens is if there is a failure somewhere else that lowers the pressure to a point where they slip. They aren't like brake pads that are expected to sacrifice themselves to get a job done. Maybe it's not the mod you did that kept the clutch from failing, maybe it just that TC clutch failure isn't a problem.

At that point, like brakes, would rub metal on metal and send that shrapnel through the tranny.
Good point! I never thought of that.

My estimate is that I need to rebuild these trans at about 250000km, anything beyond that and it's going to start to slip, burn the 3/4 clutch, and throw P1870 codes.

My gut instinct says that replacing parts out of fear is not a good strategy. I always want to find out if the part is really bad before doing that. Transmission repair seems to have a high fear factor associated with it. "Always replace the steels" is another one - when I talk to guys that do this for a living they say they reuse the steels all the time as long as there are no major burn marks or warpage but ask on a forum and the same answer keeps coming up - "Steels are cheap, why take the chance".

I'm going to roll the dice on this one, I'm betting that the TC is mostly clean but I'll flush it anyway. I'm also betting that the clutch isn't worn out to any great degree and won't fail and take out the transmission.

I'll post up if it causes any problems in the future.
 
Sep 17, 2018
34
Iowa
Saying that the friction disc in a converter doesn't wear out is wholeheartedly false

Tq converters in 4l60e, 4l80e, and 6l80e all have issues with failure.
4l60e converters in factory form have a pwm apply and will have a fair amount of slip on apply and release, and also during any shift where the converter may already be locked.

This got even worse when DOD/AFM was introduced.
With DOD/AFM the tq converter is PROGRAMMED to slip. On purpose. Up to 60 rpm
Even in engines without DOD/AFM...they still share the slip programming (albeit a lower slip #...usually more like 20rpm)

When I say they slip on purpose...they have input shaft rpm sensor and will vary the TCC solenoid duty to get the converter to slip the clutch. If the sensors show that there is 20 rpm of slip, and it is programmed to have 60...it will lower the clutch apply pressure until the slip value reaches 60rpm

Earlier units that didn't have this control, still had a fairly complex pwm table that would vary the duty in the same way, but it's not closed loop where it targets a slip value. It is just based off of load. So they still definitely slip.
You can modify the tune for 100% pwm minimum which you'd think would be no slip...but if there is wear in the valve body at the TCC Regulator valve, you will not have adequate apply pressure and the clutch will STILL slip.
You can modify the valve body for a true On/Off apply with full pressure all the time and that's your best bet...but there will still be wear whenever the clutch applies or releases. Just like any other clutch

When it comes to re-using the 4l60e tq converter...it's a bad play. If it is your personal unit and you want to save some money and gamble...fine. But it's for sure a gamble.
You ask "how often have you seen converter issues" on a 60e...ALOT. Alot alot.
The tq converter is a massive source for debris and when the clutch wears out, you get metal on metal and the debris is very fine and it causes a total mess. It'll also plug a cooler and smoke a pump.

Furthermore, you say "it'll only affect highway mileage" and that's not correct. It can hurt the rest of the unit as mentioned above. But it can also end up hurting itself. If You continue to run it that way long enough, it will wear out the drive cover and piston, allow for enough internal clearance in the converter, and the turbine can move enough that bearings/thrust washers get slammed and ruined and then locks stuff up or breaks a stator or ruins splines etc.

Your notes on th350 converter is totally irrelevant to a lockup converter.
If the trans was OK when you tore it down, not full of debirs, and you assume the converter is healthy...you can modify the valve body for full pressure lockup and you'll likely land on the fortunate side of risk on this deal.

To put it most simply...it's like wearing 3 day old underwear for a date. CAN you? Sure.
Will you even get lucky...possibly.
But if you're going to take the time to shower and put cologne on...I'd put on clean underwear too
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,151
Brighton, CO
I have had 3 Torque Converters wear out. One on my Wifes Pontiac, one on my Envoy, and one on my 1981 Cadi (many years ago).

Its one of those things where you have to take it out, and to just replace a TQ Converter later, you have to go thru the same process.

Just get a new one, fill it up, and slap it in there.
 

JayArr

Original poster
Member
Sep 24, 2018
531
Mission BC Canada
OK, you've convinced me.

It's just that spending $450 on a part that I can't test or prove is bad is disconcerting.
 
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JayArr

Original poster
Member
Sep 24, 2018
531
Mission BC Canada
That's part of why I wanted to re-use the original TC.

For some reason they are double the price up here. The big distributor up here is a place called King O Matic, they sell all the kits and parts for transmissions but they aren't very good to deal with. I've had trouble getting correct parts from them and even when my parts person gives me the very best discount they are still very expensive. Last quote was $485Cdn with taxes.

So last transmission I got a rebuilt from Rock Auto (TC Reman) and it looked like it was going to save me half but after I factored in the return freight to get my core charge back it was still about $265Cdn and I had to spend a Saturday morning driving across the line to get it. Better but still nothing like your price at the counter at NAPA.

It's easy to say "why take the chance" when the part is $125USD ($170Cdn), when it's $360USD ($485Cdn) it's a harder logic to swallow.

Maybe I can get the NAPA in Sumas WA to order in the part and then drive down and do a swap. that would eliminate the $100 in freight it cost me last time to return the core to Rock Auto.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,151
Brighton, CO
What about getting a Reman from Advance Auto Parts, or AutoZone?

Then you could have them ship it to home if ordered online. Which is usually free if you spend over a certain amount.
 

Mooseman

Moderator
Dec 4, 2011
25,487
Ottawa, ON
Not to Canada
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,151
Brighton, CO
You canucks always messing me up LOL
 
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