Grenaded Pump
Thread Starter
Teching In
Joined: Feb 2014
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Grenaded Pump I have a 2000 Silverado 1500 with a 5.3 and 4l60e. The trans was rebuilt by a reputable shop about 40K ago. We've had no issues with it until a few months ago. It drove home just fine, and then wouldn't go into any gear the next morning. we tore it down and found a shattered pump rotor. we put in a good pump and new rotor and put it back together. Drove it for about 50 miles and started up a small hill and lost all gears again. tore it down again and found another shattered rotor. Ideas?
TECH Junkie
Joined: May 2012
Posts: 3,050
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From: Poplarville, MS
Is the converter pilot fitting into the back of the crankshaft? Is the area in the crankshaft where the converter pilot fits in good condition? Is the oil pump drive hub on the converter bent? Was the fluid level low or were you driving up a steep grade?
Moderator
Joined: Aug 2010
Posts: 7,323
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From: Ann Arbor, MI
I don't think I'm going too far out on a limb to say most grenaded pump rotors are caused by improper torque converter installation.
Be sure the converter is fully seated in the trans before bolting up the trans. The converter's mounting pads must be at least 1" behind the plane of the bell housing; 1-1/4" is typical. Then, to be absolutely safe, at first barely tighten the trans to block bolts and then use a 1/8" drill bit to make sure you still have clearance between the flexplate and converter mounting pads. (If the bell housing is flush with the block and you only have 1/16" clearance, this is still OK; they just has to be some clearance.)
And of course everything that Mr Bond said above. A grenaded rotor is probably requires a new/rebuild pump as it likely put groves into the pump halves and/or you might have a bent stator shaft, very loose bushings or other pump misalignment.
Be sure the converter is fully seated in the trans before bolting up the trans. The converter's mounting pads must be at least 1" behind the plane of the bell housing; 1-1/4" is typical. Then, to be absolutely safe, at first barely tighten the trans to block bolts and then use a 1/8" drill bit to make sure you still have clearance between the flexplate and converter mounting pads. (If the bell housing is flush with the block and you only have 1/16" clearance, this is still OK; they just has to be some clearance.)
And of course everything that Mr Bond said above. A grenaded rotor is probably requires a new/rebuild pump as it likely put groves into the pump halves and/or you might have a bent stator shaft, very loose bushings or other pump misalignment.
TECH Junkie
Joined: Dec 2012
Posts: 3,615
Likes: 1,327
From: Iowa
there's a long list of things that can cause pump rotor failure
After breaking multiple rotors in personal test vehicles experimenting, here's a short list of the most common factors
1. improper install. it's comical and sad how often people screw this up
2. torque converter runout. I won't make a list of who's good and who's bad...but I've seen hubs as much as .020+ out and it may take a week or a month...but eventually the rotor breaks
3. cavitation. especially during high demand
4. pump slide travel over-activity. This is easily remedied but many don't pay it enough attention
5. pump vane directionality. I know guys that just toss the rotor vanes in ***** nilly and that is not right. If you're reusing the rotor vanes (which is fine or even preferrable to new vanes every time) they have a proper directionality to install
6. rotor design. 13 vane is weakest. 10 is my typical go-to. 7 I reserve for only extreme high rpm applications
After breaking multiple rotors in personal test vehicles experimenting, here's a short list of the most common factors
1. improper install. it's comical and sad how often people screw this up
2. torque converter runout. I won't make a list of who's good and who's bad...but I've seen hubs as much as .020+ out and it may take a week or a month...but eventually the rotor breaks
3. cavitation. especially during high demand
4. pump slide travel over-activity. This is easily remedied but many don't pay it enough attention
5. pump vane directionality. I know guys that just toss the rotor vanes in ***** nilly and that is not right. If you're reusing the rotor vanes (which is fine or even preferrable to new vanes every time) they have a proper directionality to install
6. rotor design. 13 vane is weakest. 10 is my typical go-to. 7 I reserve for only extreme high rpm applications
Thread Starter
Teching In
Joined: Feb 2014
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Thanks for the answers. The weird thing about it though, is that it took 4 years to break the first one, then a week for the second one. We're not sure at this point if it's worth dumping money in. The truck has 200k or so and has several other things to fix. If we could fix it for $5-600 I would. But $1000+ it's not worth that much. I'll pull the 5.3 and part the rest.
