4L60e front pump failure
4L60e front pump failure 
Hey guys, I wanted to share a few pictures from a front pump failure I had. I bought this transmission new and drove it for about 800 miles before the front pump failed. The place I bought the transmission from never gave me a good reason why the pump failed and I’m not sure you can tell much from the pics. Just looking for some expert advice on what may have caused this. Thanks
TECH Junkie
Joined: Jun 2008
Posts: 3,203
Likes: 1,391
From: Nitro Alley
I did not want to be the one who said anything, but...
Excluding the cylindrical filter-element; the parts in that pump do NOT look new.
This is not 100% certain, but It looks as if someone threw a used/ worn pump into the transmission.
Excluding the cylindrical filter-element; the parts in that pump do NOT look new.
This is not 100% certain, but It looks as if someone threw a used/ worn pump into the transmission.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
When you say "new" do you mean really new from GM? Or a rebuild? I suspect the later.
The failure point is not obvious to me, but the wear on the rotor and surfaces on the pump halves is excessive. Many rebuilders will re-use marginal rotors and pump halves. Very good rebuilders will re-machine the pump halves and use a new rotor.
Actually, the failure point could be below the pump slide where the ring and o-ring should be in good condition; else pressure will leak out of there.
The failure point is not obvious to me, but the wear on the rotor and surfaces on the pump halves is excessive. Many rebuilders will re-use marginal rotors and pump halves. Very good rebuilders will re-machine the pump halves and use a new rotor.
Actually, the failure point could be below the pump slide where the ring and o-ring should be in good condition; else pressure will leak out of there.
When you say "new" do you mean really new from GM? Or a rebuild? I suspect the later.
The failure point is not obvious to me, but the wear on the rotor and surfaces on the pump halves is excessive. Many rebuilders will re-use marginal rotors and pump halves. Very good rebuilders will re-machine the pump halves and use a new rotor.
Actually, the failure point could be below the pump slide where the ring and o-ring should be in good condition; else pressure will leak out of there.
The failure point is not obvious to me, but the wear on the rotor and surfaces on the pump halves is excessive. Many rebuilders will re-use marginal rotors and pump halves. Very good rebuilders will re-machine the pump halves and use a new rotor.
Actually, the failure point could be below the pump slide where the ring and o-ring should be in good condition; else pressure will leak out of there.
The company that built the transmission said that was a possible cause of the failure but I had an 1/8” between the converter and flexplate when I put the transmission in and Yank said the SS3600 has an anti-ballooning plate. I didn’t do anything different when I put the transmission back in so I’ll hope it doesn’t happen again. I originally thought when I saw the pics that the pump may have been starved of trans fluid and caused the damage. The transmission never slipped before this happened.
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TECH Junkie
Joined: Jun 2008
Posts: 3,203
Likes: 1,391
From: Nitro Alley
I can not say for sure what happened, but...
In the mechanical world (or any industry involving assembly within close tolerances) there is the possibility of "Stacked tolerances" or "Tolerance Stack-Up".
Lets say 4 equally sized parts need to fit together inside of a 1.5" tall space with a 0.5" gap of clearance left over.
In a perfect world... each part would be 0.25" tall.
However in reality these parts may actually be 0.23" with a 0.01" to 0.03" variance in either direction.
The part could be anywhere from 0.20" to 0.26".
The 4 parts will fit in the 1 inch tall space most of the time...
However, for example if we have 2 parts that are 0.25" tall and 2 parts that are 0.26" tall.
This would mean that we have a 1.02" tall assembly of the 4 parts.
This does not give us 0.5" clearance in a 1.5" tall space... we have 0.48" of clearance.
This makes for an unacceptable amount of clearance.
Yes the 1.02" tall parts will fit in the 1.5" space... what I did not tell you is the purpose of the 0.5" required clearance.
The 0.5" clearance is for the parts to grow when temperatures increase.
We need 0.5" of clearance for our 4 parts to grow and not crush each other.
Lets just say that the 0.48" clearance is not enough and our 4 parts do crush each other and fail.
This can actually happen between the pump rotor, pump halves, torque-converter ETC...
Normally the stock rotor will break apart or crack in 2 pieces...
You do not have a broken rotor... but could the excessive wear be from not blue-printing the pump clearances, and not setting the torque-converter depth properly?
Yes possibly... but the plastic rotor guide is not new (discolored from being in old oil), the stator-support tube is rusty, and there is a high amount of wear and tear in the pump...
In the mechanical world (or any industry involving assembly within close tolerances) there is the possibility of "Stacked tolerances" or "Tolerance Stack-Up".
Lets say 4 equally sized parts need to fit together inside of a 1.5" tall space with a 0.5" gap of clearance left over.
In a perfect world... each part would be 0.25" tall.
However in reality these parts may actually be 0.23" with a 0.01" to 0.03" variance in either direction.
The part could be anywhere from 0.20" to 0.26".
The 4 parts will fit in the 1 inch tall space most of the time...
However, for example if we have 2 parts that are 0.25" tall and 2 parts that are 0.26" tall.
This would mean that we have a 1.02" tall assembly of the 4 parts.
This does not give us 0.5" clearance in a 1.5" tall space... we have 0.48" of clearance.
This makes for an unacceptable amount of clearance.
Yes the 1.02" tall parts will fit in the 1.5" space... what I did not tell you is the purpose of the 0.5" required clearance.
The 0.5" clearance is for the parts to grow when temperatures increase.
We need 0.5" of clearance for our 4 parts to grow and not crush each other.
Lets just say that the 0.48" clearance is not enough and our 4 parts do crush each other and fail.
This can actually happen between the pump rotor, pump halves, torque-converter ETC...
Normally the stock rotor will break apart or crack in 2 pieces...
You do not have a broken rotor... but could the excessive wear be from not blue-printing the pump clearances, and not setting the torque-converter depth properly?
Yes possibly... but the plastic rotor guide is not new (discolored from being in old oil), the stator-support tube is rusty, and there is a high amount of wear and tear in the pump...
Last edited by vorteciroc; Feb 20, 2021 at 06:03 PM.
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Verdad Gallardo TECH Junkie
Joined: Jun 2008
Posts: 3,203
Likes: 1,391
From: Nitro Alley
The company that built the transmission said that was a possible cause of the failure but I had an 1/8” between the converter and flexplate when I put the transmission in and Yank said the SS3600 has an anti-ballooning plate. I didn’t do anything different when I put the transmission back in so I’ll hope it doesn’t happen again. I originally thought when I saw the pics that the pump may have been starved of trans fluid and caused the damage. The transmission never slipped before this happened.
or the seal that goes into the pump for the filter is: wrong, or not replaced with the filter and is old/ leaking, installed incorrectly (crooked or double-stacked), ETC...
TECH Junkie
Joined: Dec 2012
Posts: 3,618
Likes: 1,328
From: Iowa
Sorry but...what do you say the failure is?
I don't see a broken rotor or slide or vanes
What made you stop and take it apart?
It is clearly scarred but I'd be looking at that bushing and I'd be worried about that.
Anywho...none of that looks good by any means...but why did it stop you from driving it? Did line pressure fade, did it start to puke fluid out the front, etc
I don't see a broken rotor or slide or vanes
What made you stop and take it apart?
It is clearly scarred but I'd be looking at that bushing and I'd be worried about that.
Anywho...none of that looks good by any means...but why did it stop you from driving it? Did line pressure fade, did it start to puke fluid out the front, etc
Staging Lane
Joined: Nov 2007
Posts: 79
Likes: 7
I'll step into this and Play the chicken or the egg game.
With the caveat,it is impossible to ascertain what happened with 100% accuracy.
But one can make some assumptions.
The worst damage is on the back side of the pump. Suggesting a axial thrust issue.
One can also identify marks on the drive gear of the pump that suggest the same axial thrust issue.
Some marking on the internal diameter of the pump drive gear indicating more wear that I would expect for 800 miles.
This suggests the vane pump may have not been replaced but isn't prof.
Not every rebuilder replaces the pump parts if they pass inspection.
A picture of the converter hub might also be helpful. As you know it was new.
Inspect the lower recess of the pump drive notch. It it has marking from the pump drive lugs I would assume its a thrust issue.
What was the flex plate to converter clearance?
Rick
With the caveat,it is impossible to ascertain what happened with 100% accuracy.
But one can make some assumptions.
The worst damage is on the back side of the pump. Suggesting a axial thrust issue.
One can also identify marks on the drive gear of the pump that suggest the same axial thrust issue.
Some marking on the internal diameter of the pump drive gear indicating more wear that I would expect for 800 miles.
This suggests the vane pump may have not been replaced but isn't prof.
Not every rebuilder replaces the pump parts if they pass inspection.
A picture of the converter hub might also be helpful. As you know it was new.
Inspect the lower recess of the pump drive notch. It it has marking from the pump drive lugs I would assume its a thrust issue.
What was the flex plate to converter clearance?
Rick
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
Rick: That's great insight and a very plausible explanation, especially for a failure after just 800 miles.
Considering your obvious knowledge and insight, why only 49 posts in 14 years? Loose the password or something?
Like MaroonMonster, I'm also curious what the symptoms of the failure were.
Considering your obvious knowledge and insight, why only 49 posts in 14 years? Loose the password or something?
Like MaroonMonster, I'm also curious what the symptoms of the failure were.
Sorry but...what do you say the failure is?
I don't see a broken rotor or slide or vanes
What made you stop and take it apart?
It is clearly scarred but I'd be looking at that bushing and I'd be worried about that.
Anywho...none of that looks good by any means...but why did it stop you from driving it? Did line pressure fade, did it start to puke fluid out the front, etc
I don't see a broken rotor or slide or vanes
What made you stop and take it apart?
It is clearly scarred but I'd be looking at that bushing and I'd be worried about that.
Anywho...none of that looks good by any means...but why did it stop you from driving it? Did line pressure fade, did it start to puke fluid out the front, etc
I'll step into this and Play the chicken or the egg game.
With the caveat,it is impossible to ascertain what happened with 100% accuracy.
But one can make some assumptions.
The worst damage is on the back side of the pump. Suggesting a axial thrust issue.
One can also identify marks on the drive gear of the pump that suggest the same axial thrust issue.
Some marking on the internal diameter of the pump drive gear indicating more wear that I would expect for 800 miles.
This suggests the vane pump may have not been replaced but isn't prof.
Not every rebuilder replaces the pump parts if they pass inspection.
A picture of the converter hub might also be helpful. As you know it was new.
Inspect the lower recess of the pump drive notch. It it has marking from the pump drive lugs I would assume its a thrust issue.
What was the flex plate to converter clearance?
Rick
With the caveat,it is impossible to ascertain what happened with 100% accuracy.
But one can make some assumptions.
The worst damage is on the back side of the pump. Suggesting a axial thrust issue.
One can also identify marks on the drive gear of the pump that suggest the same axial thrust issue.
Some marking on the internal diameter of the pump drive gear indicating more wear that I would expect for 800 miles.
This suggests the vane pump may have not been replaced but isn't prof.
Not every rebuilder replaces the pump parts if they pass inspection.
A picture of the converter hub might also be helpful. As you know it was new.
Inspect the lower recess of the pump drive notch. It it has marking from the pump drive lugs I would assume its a thrust issue.
What was the flex plate to converter clearance?
Rick
Staging Lane
Joined: Nov 2007
Posts: 79
Likes: 7
Originally Posted by mrvedit
Considering your obvious knowledge and insight, why only 49 posts in 14 years? Loose the password or something?
Every mechanic should have to rebuild transmissions and suffer the consequences when something goes wrong.
It will make you a better mechanic than 90% of them.
Last edited by mrvedit; Feb 24, 2021 at 10:45 AM. Reason: Moved post from another thread
TECH Junkie
Joined: Dec 2012
Posts: 3,618
Likes: 1,328
From: Iowa
Converter ballooning is an issue few and far between.
A stock 4l60e converter can and does regularly see line or near line pressure when under lockup.
Basically any decent performance converter now a days is incredibly unlikely to balloon.
The front pump bushing looks freaking smoked. What's the story there?
The pump does look very scarred but no real evidence of chicken vs egg. Looks like spacing issue somewhere in the pump stackup.
A stock 4l60e converter can and does regularly see line or near line pressure when under lockup.
Basically any decent performance converter now a days is incredibly unlikely to balloon.
The front pump bushing looks freaking smoked. What's the story there?
The pump does look very scarred but no real evidence of chicken vs egg. Looks like spacing issue somewhere in the pump stackup.
Converter ballooning is an issue few and far between.
A stock 4l60e converter can and does regularly see line or near line pressure when under lockup.
Basically any decent performance converter now a days is incredibly unlikely to balloon.
The front pump bushing looks freaking smoked. What's the story there?
The pump does look very scarred but no real evidence of chicken vs egg. Looks like spacing issue somewhere in the pump stackup.
A stock 4l60e converter can and does regularly see line or near line pressure when under lockup.
Basically any decent performance converter now a days is incredibly unlikely to balloon.
The front pump bushing looks freaking smoked. What's the story there?
The pump does look very scarred but no real evidence of chicken vs egg. Looks like spacing issue somewhere in the pump stackup.
Last edited by td1168; Feb 24, 2021 at 03:40 PM.