fmx breaking front pumps

fmx breaking front pumps

Joined: May 9th, 2010, 5:23 pm

July 4th, 2010, 10:33 pm #1

I've got a 351c built up and balanced. Anyway when i put the engine and trans in the car it would move for a short time then stopped pumping fluid. changed the pump put back in car and it worked again short time stopped pumping fluid. took back out of car changed pump and converter still no fluid. Put in a used trans today it went into reverse and when wouldn't go into any gears. pulled the lines and started car no fluid. Why? could my converter piolt be to small for the crank. I tried to measure them with a tape and they appear the crank is a hair bigger then the converter. Very frustrated. motor hasn't made it around the block and has been 2 yrs since it ws built. Please help me get this to move lol.
Last edited by showtime71 on July 4th, 2010, 10:34 pm, edited 1 time in total.
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truckdoctor
truckdoctor

July 5th, 2010, 1:05 am #2

hi you may have a problem with the flywheel/ringear ether putting presure on the pump lugs or not engaging into the lugs proper ether way you will have major problems.
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Joined: May 9th, 2010, 5:23 pm

July 5th, 2010, 12:06 pm #3

pump lugs or do you mean converter studs? how can the flywheel put pressure on the pump? just asking cause i'm not fallowing and the frustration level is clowding my brain lol. I'm taking the trans out this morning and going to get a caliper to measure the converter hub and my crank hole do you know what the tolerance is suppose to be or as long as the converter is small and fits inside the crank its ok? I've never run into this type of problem before and have changed alot of trans. I was going to put a c4 on that i know is good but the flywheel was to big for the bell housing so went with another fmx. Ok just got the trans back out couldnt get the pump off to check so going to take to trans shop tomarrow. I just noticed that the dust plate that goes on th engine in front of the flywheel is missing. so in other words the bell housing is being bolted directly to the block. could that be the problem? I dont think so were only talking about a 1/16 -1/8 thick. What you guys think?
Last edited by showtime71 on July 5th, 2010, 2:24 pm, edited 1 time in total.
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Joined: November 18th, 2004, 4:20 am

July 5th, 2010, 3:16 pm #4

I've got a 351c built up and balanced. Anyway when i put the engine and trans in the car it would move for a short time then stopped pumping fluid. changed the pump put back in car and it worked again short time stopped pumping fluid. took back out of car changed pump and converter still no fluid. Put in a used trans today it went into reverse and when wouldn't go into any gears. pulled the lines and started car no fluid. Why? could my converter piolt be to small for the crank. I tried to measure them with a tape and they appear the crank is a hair bigger then the converter. Very frustrated. motor hasn't made it around the block and has been 2 yrs since it ws built. Please help me get this to move lol.
How are you installing the transmission?
In one piece or convertor separate?

It must be installed as a complete assembly.


When the transmission is installed the convertor should be able to be wiggled before the nuts are tightened.

If there is no wiggle the pump can be toasted in a very short time.

Test fit the convertor in the crank/flex plate.

The convertor pilot must fit into the crank while the studs must fit into the flex plate without any conflict.

There are no "lugs" on an FMX convertor, rather they are flat areas that drive the pump.

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Joined: May 9th, 2010, 5:23 pm

July 5th, 2010, 3:47 pm #5

I'm installing as one piece w/converter on the trans. When i took the trans out this morning i looked and the converter was tight up to the back of the flywheel so I'm assuming the hub is fitting into the crank but will measure with a calipers tomarrow. This motor was rebuilt and balanced by very good shop (professional) but the crank used was in a motor that had rod failure. Starting to wonder if my crank isnt bent causing a wabble. I would assume they would have caught that in the balancing or assembly stages though. Thanks and I'll keep you informed. P.s. what kind of problems do you think i'd come accross if I went to a manual?
Last edited by showtime71 on July 5th, 2010, 3:49 pm, edited 1 time in total.
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***no login***
***no login***

July 5th, 2010, 5:51 pm #6

If the problem is in your motor, going to a different transmission will only cause a whole new slough of problems.

You did not define what you mean by "breaking front pumps" so it is kind of hard to determine exactly what is going wrong here. You do state that it quits pumping fluid, but you do not tell us why. All we know is that something is causing loss of pumping, but no idea exactly what. Could you tell us exactly what you mean when you say "breaking front pumps?"
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Joined: May 9th, 2010, 5:23 pm

July 5th, 2010, 6:10 pm #7

I've had 3 pumps in one trans and 2 converters. 1 pump had the gear inside broke in half and the most recent one had score markings and grey (metal) in it. The tranny I put in yesterday and took out today i cant get the pump out to inspect but the converter spun fine until i put it back in it spun hard and actually stopped and i couldnt turn it at all. I pulled it back off and tried again and got it all the way on but it turns hard. I'm going to talk to my engine builder to see what he thinks and I'll also be dropping the latest trans at the shop for inspection and rebuild. All i know is they all work for short time or in one case just a few minutes and the end result is no fluid flow in the lines. this doesn't make sence to me. If i dont have a fit or alignment problem what else would be taking out the pumps? Thanks for the help.
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truck.doc
truck.doc

July 5th, 2010, 9:28 pm #8

it is very important that when you install the trany that when the studs are aligned and the trans is tight to the bell that you have foward and back movement of the torque (kinda floating back and forth ) otherwise you will damage the pump gear as you indicated scored or cracked and the tras sheild is a good idea otherwise you may have the wrong fliweel ring gear combo. always doubble check this as it can ruin a perfectly good trans.
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Joined: May 9th, 2010, 5:23 pm

July 5th, 2010, 11:10 pm #9

How do you get forward and backward movement on the torque converter after its bolted tight to the flywheel?
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Joined: November 18th, 2004, 4:20 am

July 5th, 2010, 11:51 pm #10

The convertor must wiggle before the nuts are tightened.

There must be some movement or it is too tight.
I'd almost suspect a flex plate problem if it's that tight.

Is the drive pump gear in correct?
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