Pump gear broke

Went to test n tune this past friday, and going into the burnout, all systems were normal. After completing my burnout, I let off the line lock and throttle and hit the brakes to roll up and as I shifted into neutral, the motor suddenly died and wouldn't spin.
After major surgery to remove the transmission, I found the cause of the problem as a broken pump gear. Anyone have an idea as to what would cause the gear to break like this? I was able get the broken gear out, but haven't been able to remove the outter gear.

I don't see any blue on them, so I guess you can rule out Heat and likely lack of oil.

I would think it is likely abuse/stress/metal fatigue from a hard life beyond it design capacity.

What's with the hole, it appears on the blow up, of the picture, in the outer gear in the first picture at 10 to 11 O'Clock?

Looks like they have the chamfer to the front, so they are in, in the right direction.

Put it in the freezer and see if the other gear will come out. If that don't work put it in the oven.

On the C6 aluminum valve bodies the freezer trick was used to check for sticking valves. On a cast iron oil pump it will be less dramatic but, it may shrink or swell something enough to loosen it.

Also Your Torque Convertor flats look a lot shorter then the inner gear slots.

Glue that center gear back together and see how much Slop it has on the Convertor.

supervel45 wrote:I don't see any blue on them, so I guess you can rule out Heat and likely lack of oil.

What's with the hole, it appears on the blow up, of the picture, in the outer gear in the first picture at 10 to 11 O'Clock? I hadn't noticed the hole until you mentioned it lol.

Looks like they have the chamfer to the front, so they are in, in the right direction.

Put it in the freezer and see if the other gear will come out. If that don't work put it in the oven.

On the C6 aluminum valve bodies the freezer trick was used to check for sticking valves. On a cast iron oil pump it will be less dramatic but, it may shrink or swell something enough to loosen it.

Also Your Torque Convertor flats look a lot shorter then the inner gear slots.

Glue that center gear back together and see how much Slop it has on the Convertor.

I am not sure about the hole. I had a local transmission shop freshen the trans up last year and when I went to put it in, the converter wouldn't turn at all. I tried a stock converter and same thing. I took it back to the shop and a couple days later he called and said it was ready and didn't really say what the cause was. So now I am really wondering because it wasnt like that before it dropped it off.
I am not taking chances this time, I ponied up and ordered a reman'd pump assembly.

You have to be careful with those C6 oil pump bushings. My Dad an I did one 12-15 years ago on his old truck that did not get driven anymore. We go by the Old Ford Shop Manual on Aligning the notch on the Bushing with the Oil Hole. Other Builders sometimes do it Differently. Like Piston Ring Gaps it seems to Change over the Years. We always double check things and all seemed fine when we test drove it. Needless to say fast forward to 2019 or 20 I ended up with the truck. The Torque Convertor seal started leaking when it got hot. The Bushing also would spin as evidenced by the inner wear marks.  Pulled the pump and checked the bushing on the torque convertor. It was snug. Went and got a new bushing and checked it and it was somewhat looser.

Now as to you getting a New/Rebuilt C6 pump that is good, Have Fun. You might call Mike Kurtz at Century Transmission in the Houston area at 281-633-8155 and tell him it is for a Race Truck and to ship you one. It's not fool proof but, he does excellent work and is a Racer will offer support after the sale.

These rebuilt pumps can be hit or miss. I see they have oversized gears for the rebuilt pumps for after they are machined, so the quality of the builder really comes into play. They are also Likely Chine/a Gears!

Also the snout of the Torque converter and the flat dimensions can vary also, you can't check the Fit Feel over the phone very well but You can give dimensions and get some Idea.

PS:1 I thought that Hole was Surely a grease spot or I was seeing "Things". Never have I seen something like that before. Only thing I could think of was some kind of Crazy Oiling Mod, I have not heard of.

PS:2 Measure the Thickness of the Gear you got out. I believe the stock Thickness is .660".

Have Fun.

Thanks for the information. The new pump is supposed to arrive tomorrow so I will pull the stator and check the gears. I will also check fit with the converter drive hub.

^You're Welcome.

^That's a good plan.  Be sure and mike/measure the Clearance of the gears across the face of the pump housing, with a straight edge and feeler gauge. Also make sure the gear chamfer is facing the front. Note the position of the bushing drain notch, to the pump oil hole, for reference, if you get a bushing problem, later.

Also if there is any grove on the convertor hub from seal wear, smooth it out with some 280/320 ect.

I feel a little loose of a fit of the bushing to the convertor is better than snug. There was quite the difference in my bushing fit on the problem child, that we have never had before.

I hate to say it but, since the trans is out, and Partially Apart, and after THIS KIND of PROBLEM, as well as not making a full pass on it, I would likely tear the whole damn thing apart for a Re-Check. At LEAST to CHECK CLUTCH CLEARANCES and DEFFENTLY CHECK YOUR END PLAY!!! If you drove it around on the Street and all was Well I might Skip some of that. NOT THE END PLAY THOUGH, AT the INPUT SHAFT!  That's just me though.

supervel45 wrote:^

I hate to say it but, since the trans is out, and Partially Apart, and after THIS KIND of PROBLEM, as well as not making a full pass on it, I would likely tear the whole damn thing apart for a Re-Check. At LEAST to CHECK CLUTCH CLEARANCES and DEFFENTLY CHECK YOUR END PLAY!!! If you drove it around on the Street and all was Well I might Skip some of that. NOT THE END PLAY THOUGH, AT the INPUT SHAFT!  That's just me though.

Yea, I am going to.

Can you check the surface clearance of the broken gear in the old pump also? Measure the Thickness of Both Gears, if you get the stuck one out?

Post the Thickness of the New pump gears along with the Old Ones, for Future Reference Also, Please.

It looks like the broken gear was making contact by the score marks on it. Sometimes trash in the system can cause that. The outer gear is not scored, so that is a tell tail that the Broken Gear may have been tighter and contacting the Stator Support. The Lack of Blue on it is Puzzling. It could have also been rebuilt that way and was already scored on assembly, who knows.

I have been around these C6's for about 4 decades, and don't recall ever seeing or hearing about this happening.

I imagine it has but, it seems to be a very rare deal.

As far as the hole on the outer gear, I just shake my head at that one. I am surprised it did not crack too. That just seams like a really bad idea.

And another thing don't forget your Air Checks after you go through it. Do Not Hit the Low/Reverse Piston, the one in the Bottom of the Case, with High Air Pressure, without the Clutch's and Snapring in, or you can/will bend the Spring Retainer Ring.

I would also put that Old Pump back together and in the Transmission, and see what kind of Endplay it had, First, Just so you will Know!

I hope you don't find anything else wrong but, now's the time to catch it, if they screwed something else up.



Did you damage the outer gear, female tooth top, at about 9:15 O'Clock in the First picture, trying to remove it?

HorsinAround wrote:

supervel45 wrote:^

I hate to say it but, since the trans is out, and Partially Apart, and after THIS KIND of PROBLEM, as well as not making a full pass on it, I would likely tear the whole damn thing apart for a Re-Check. At LEAST to CHECK CLUTCH CLEARANCES and DEFFENTLY CHECK YOUR END PLAY!!! If you drove it around on the Street and all was Well I might Skip some of that. NOT THE END PLAY THOUGH, AT the INPUT SHAFT!  That's just me though.

Yea, I am going to.

I would try to get a hold of Frank Merkl who is a member here.
I don't know of anyone who knows more about the workings of a C6 transmission.

I was hoping he would see this and chime in, but I will send him a pm.

Thought I would share Frank's reply here in case someone else has the issue.

"seen it a couple times , pump gears put in backwards or not enough coverter pull out
Frank"

Here is a followup on the pump gears.

I took the converter to a local shop to get checked over. He said it have ALOT of run out and that is probably what took out the gears. And this is a new converter.
https://photos.app.goo.gl/vmWCaDSS39ucL4427


He also said there is no way it would hold the power I have and it was supposed to have been built to handle over 900 with up to a 300 shot. So this makes 2 converters that came from a company that were supposedly built for my application that I have had trouble with. Time to find another converter company.

That sucks. I had a TCI that had a problem and when we went to cut it open on the lathe you could see the run out. They did not have everything centered up when they welded it.

I would be pissed but, that's the breaks with this kind of stuff. Hope they make it right.

WOW !! That could well be what caused the damage . That's very average

Gregaust wrote:WOW !! That could well be what caused the damage . That's very average

thats average?

Should have put a Dial Indicator on it. I watched the rectangular fixture behind it at the end of the hub. It moves up and down quite a bit.

I'd bet an easy .030" or more run out.

Mine did not take out the other brand pump and I had completely forgotten about it on your deal, until you posted the Video. It may have been part of my Flex Plate Problems Though.

This Thread will be Excellent for anyone in the Future Now that has this Problem.

You gonna Pony up for a Two Piece Coan?

supervel45 wrote:Should have put a Dial Indicator on it. I watched the rectangular fixture behind it at the end of the hub. It moves up and down quite a bit.

I'd bet an easy .030" or more run out.

Mine did not take out the other brand pump and I had completely forgotten about it on your deal, until you posted the Video. It may have been part of my Flex Plate Problems Though.

This Thread will be Excellent for anyone in the Future Now that has this Problem.

You gonna Pony up for a Two Piece Coan?

They quoted me an 8" deal at $1400. I'd love to got to a 2 piece, but, not yet. Still trying to recover from the bill on the engine, and now this.. Trying to remember why I do this racing crap.. lol.