Line bore = cracked convertor??

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stroker_valiant

stroker_valiant

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I think I cracked the hub on my convertor again, this will be the second time I have done so. When I stand on the throttle, and bring the car up through the gears, it starts dumping trans fluid out of the bell housing. The car did this a few months ago, and cracked the hub on the convertor, where the hub meets the convertor body (the side that goes into the trans pump). Before this happened, I could drive the car all day around town with light throttle, so it happened when went full throttle. I have not had the trans out yet to verify this is what happend again, but i'm pretty sure thats the case. The only thing I can think of is that the block was line bored at one point in its life. When I built this motor, I did not check crank runout, basically first motor build ever and did not know to do so. I think I have a good idea of how to check it now, but are there any other ideas as to why I keep cracking convertor hubs??? If I didn’t make this clear enough to understand the problem, ask and I will clarify.

360 block 4 inch stroke
Internal balance
904 reverse manual valve body
9 inch 3500 stall convertor
 
maybe an issue with the thrust bearing in your engine allowing the crank to walk back towards the trans. at high RPM ??
 
I will be pulling the trans this weekend hopefully, can endplay be checked on an assembeld running motor without to much intrusion of the block??
 
when you line bore the block it still SHOULD be centered...

i would look at the thrust of the crank...

you could throw a manual bell on it and just use that to measure to see if it "wobbles"...

could the flex plate be on backwards causing it to shove the converter into the pump?
 
Flex plate is on correct, that I know for sure. It is an SFI Mopar Perf. Plate FYI. When putting the unit together, the convertor is pulled back toward the motor what, like 3/8 inch or so? So it isn’t pushing into the pump, unless it is flexing THAT much…What would be the point of the manual bell? I’m confused by that. I understand that the crank is centered left right during line bore, but it would be physically raised in the block .004 or .006 or whatever was cut out, correct yes? I believe thats where my problem lies.
 
I would check to see if the trans is centered with the crank center line you may have a situation that requires the use of offset dowels.
 
Purple Haze said:
I would check to see if the trans is centered with the crank center line you may have a situation that requires the use of offset dowels.
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And that is exactly what I was thinking! I have a few different kinds of magnetic base indicators I can use to get an accurate reading.
 
I have seen this sort of thing often enough to check it before I put a transmission together.

Manufacturing tolerances can stack up. Across decades of manufacturing, and rebuilding you can wind up with a block / bellhousing / transmission that does not line up.

It can be checked. It should be checked when you start dealing with 40 year old parts. I have seen a brand new scattershield that was bad too... Here is how I check that:

With the flywheel removed, secure a dial indicator to the end of the crankshaft. Mount the bellhousing to the block, and check the runout of the locating bore on the bellhousing with the dial indicator.

Obviously this is much easier to do when you build the engine. I always check a bellhousing or transmission case on the block with only a crank in it. This is a real pain with a C6 transmission, and very easy with a separate transmission bellhousing.

Hope you find the problem, whatever it maybe.

B.
 
Thank to all for the replies, this just confirms what I was allready thinking.

Bohica, you make a good point, thanks.

Ill have it tore apart in about a week and let you know what the measurments are...
 
What year of engine and transmission you running? If you have a 1967 back transmission and a 1968 up crankshaft in the engine the hub on the convertor may be too small and causing problems with your convertor. It would be causing run out.
 
clock the transmissions bell housing to the block, offset dowl pins=runout check....afterthat...check the convertor shell's construction/dimensions .

also make sure the hub fits the register and is not too small.
 
Oklacarcollecto said:
What year of engine and transmission you running? If you have a 1967 back transmission and a 1968 up crankshaft in the engine the hub on the convertor may be too small and causing problems with your convertor. It would be causing run out.
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1980 Model block, Eagle crank Trans is 70's or newer, I dont remember exactly, but its not the older one like you speak of.
 
It could be just a poor quality hub on the converter too. Or a mismatch with the pump lugs. To check the crank centering, you'll need to pull your trans completely apart to where you just have the case bolted onto the block. Have fun!
 
I had the same problem with a cracked snout(8 inch Coan 4500 stall)with my stroked 410.I had my tranny builder put a dial indicator on the back of my block(1977 360)He told me it was within tolerance(I think .005 or .05)replaced the snout,put all back together and haven,t had a problem since(another 100 passes,1/4 mile).Have you had your driveshaft balanced ever?Just a thought,good luck.
 
cudamark said:
It could be just a poor quality hub on the converter too. Or a mismatch with the pump lugs. To check the crank centering, you'll need to pull your trans completely apart to where you just have the case bolted onto the block. Have fun!
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To get away from doing what you are saying, isn’t the end result the same this way: Magnetic base dial indicator magnetized to the crank / flex plate, convertor removed but trans reinstalled. Set the dial arm at a zero lash to trans input shaft, and rotate the crank by hand from the front of the motor and measure the variance. I understand this does not check alignment of the block to the bell housing, but it would check the alignment of the crank to the trans input correct??
 
pettybludart said:
I had the same problem with a cracked snout(8 inch Coan 4500 stall)with my stroked 410.I had my tranny builder put a dial indicator on the back of my block(1977 360)He told me it was within tolerance(I think .005 or .05)replaced the snout,put all back together and haven,t had a problem since(another 100 passes,1/4 mile).Have you had your driveshaft balanced ever?Just a thought,good luck.
Click to expand...

Driveshaft was cut down when the 8 3/4 went in and rebalanced, to what speed it was balanced I do not know though.
 
stroker_valiant said:
To get away from doing what you are saying, isn’t the end result the same this way: Magnetic base dial indicator magnetized to the crank / flex plate, convertor removed but trans reinstalled. Set the dial arm at a zero lash to trans input shaft, and rotate the crank by hand from the front of the motor and measure the variance. I understand this does not check alignment of the block to the bell housing, but it would check the alignment of the crank to the trans input correct??
Click to expand...
Maybe if you ran the dial indicator against the machined section of the reaction shaft you could get an accurate reading but how would you see the gauge to read the runout? I'm not even sure you have enough room to get the gauge in there. You can't do it against the imput shaft as it's fully splined and the shaft will move side to side anyway. Maybe if someone made a machined sleeve that fit tight over the imput shaft and tight against the reaction shaft so everything stays centered......hmmmm.......
 
cudamark said:
Maybe if you ran the dial indicator against the machined section of the reaction shaft you could get an accurate reading but how would you see the gauge to read the runout? I'm not even sure you have enough room to get the gauge in there. You can't do it against the imput shaft as it's fully splined and the shaft will move side to side anyway. Maybe if someone made a machined sleeve that fit tight over the imput shaft and tight against the reaction shaft so everything stays centered......hmmmm.......
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agreed. I don't think there is any way possible you could do it without disassembling the trans.
 
When you shut the car off, have you ever experience engine "run on",
where i whheezes and turns backwards?
 
I am not a Torqueflite expert.

Having said that, I know on other brands you can yank the pump out & indicate the bore it was in.

Hope you can find a way to get this done without gutting the transmission.

B.
 
..................Yup, totally dissambley..............ur in 4 a very long day..........get a good , name brand verter, the cheap 1s crack alot of times....I'll bet ur pump bushing is too loose, letting the verter wobble.....1 reason not 2 use a 904..........kim........
 
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