743 u-joint again

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kap258

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Does anyone know why a 743 would throw a new u-joint? I replaced it and in the first half hour of operation it threw it into the radiator. I torque it and used loctitie like ya'll reccomended last time. Any ideas I would appreciate it. This is starting to get very expensive.
 

sterlclan

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Are the pump mounts all good? How about the motor mounts? Sounds like an alignment issue to me Jeff
 

Tazza

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Are the pump mounts all good? How about the motor mounts? Sounds like an alignment issue to me Jeff
My thoughts too.
They must be in almost perfect alignment, i think the manual shows that they can be out about 1/4” no more.
 

WebbCo

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My thoughts too.
They must be in almost perfect alignment, i think the manual shows that they can be out about 1/4” no more.
Taz is right, alignment issue. Check it all out when you pull it, the shafts and splines could be suspect too.
 

kap258

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My thoughts too.
They must be in almost perfect alignment, i think the manual shows that they can be out about 1/4” no more.
The motor mounts are brand new. Replaced them and the engine 4.5 hours ago. How can you check the alignment? There is no room to see it to determine the alignment that I can tell. Please advise if there is a way. I pulled the engine and looked over the ujoint. It broke at the coupling. Where I attached it to the plate on the engine and where I attached it to the spleen was intact. Is it possible to have part failure? When it broke, pieces were blown into the radiator and also cracked alot of fins off the blower. Will the blower need to be replaced and or balanced? Thanks
 

skidboy

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The motor mounts are brand new. Replaced them and the engine 4.5 hours ago. How can you check the alignment? There is no room to see it to determine the alignment that I can tell. Please advise if there is a way. I pulled the engine and looked over the ujoint. It broke at the coupling. Where I attached it to the plate on the engine and where I attached it to the spleen was intact. Is it possible to have part failure? When it broke, pieces were blown into the radiator and also cracked alot of fins off the blower. Will the blower need to be replaced and or balanced? Thanks
Did the bolts break ?,Iwould like to see some pics. of the broken bits
 

Tazza

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Yes, they did. I will try to post some pics.
I would get it balanced for sure if you lost fins. You don't need extra vibration back there. I would hate to think what a new fly wheel would cost.....
My manual shows what the height to the centre of the spline on the pump should be off the bottom of the engine bay. I can check this out for you if needed. If you have new engine mounts, the engine should be sitting at the rite height.
I hope you get it all sorted out.
 

Tazza

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I would get it balanced for sure if you lost fins. You don't need extra vibration back there. I would hate to think what a new fly wheel would cost.....
My manual shows what the height to the centre of the spline on the pump should be off the bottom of the engine bay. I can check this out for you if needed. If you have new engine mounts, the engine should be sitting at the rite height.
I hope you get it all sorted out.
OOH, as mentioned in other threads, make sure you remove all traces of dirt and grease to ensure the U-jounts fit snug against the mounting plates. From memory i got into mine with a wire buff to remove rust and grease.
 

Fishfiles

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Did you replace just the 2 joints or did you replace the velocity ring and the center yoke ( is what I call it ) the piece that is in the middle of the two u-joints , you may be out of balance on the velicity ring or maybe the splined yoke's splines are worn and it's a loose fit there , , did you grease the new joints after installing them , did you notice any vibration during the 1/2 hour or so you say it ran , I think new bolts and straps would also be in my parts list for round 3
 

kap258

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Did you replace just the 2 joints or did you replace the velocity ring and the center yoke ( is what I call it ) the piece that is in the middle of the two u-joints , you may be out of balance on the velicity ring or maybe the splined yoke's splines are worn and it's a loose fit there , , did you grease the new joints after installing them , did you notice any vibration during the 1/2 hour or so you say it ran , I think new bolts and straps would also be in my parts list for round 3
I replaced both u-joints and the center between them. According to the parts manual they call it a coupling. The new joints were attached to the coupling. I replaced the bolts that attach to the yoke and the the bolts that attach it to the plate on the engine. I greased all the zerk fittings and spline. There was no vibration. It was actually running really well. Looking over the pieces it looks like a bolt broke that connected the two u-joints to the coupling.
 

skidsteer.ca

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I replaced both u-joints and the center between them. According to the parts manual they call it a coupling. The new joints were attached to the coupling. I replaced the bolts that attach to the yoke and the the bolts that attach it to the plate on the engine. I greased all the zerk fittings and spline. There was no vibration. It was actually running really well. Looking over the pieces it looks like a bolt broke that connected the two u-joints to the coupling.
May have been a fluke, poor bolt, ujoint etc but not as likely as its trying hard to tell you something, check and recheck everything closely. I know that not much help.
I do feel for you, have been in simular situation many times and there is usually a reason the parts flew.
Ken
 

A.G.

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After you get done checking other causes, consider this there is a right way to install a u joint. Most guys say, "Hell yes there is, you have to able to grease it!" I found out while farting around with lifted 4x4s with big tires and high torque, the grease fitting needs to be under compression. The grease fitting is a hole in the u joint, and if the driving yoke compresses that hole into the driven yoke they will suffer less failure. If the hole for the grease fitting is being pulled apart by the two yokes they bite the dust more often. Seems far fetched for your application, more like mud boggin with big tires. .02 A.G.
 

farmboy55

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After you get done checking other causes, consider this there is a right way to install a u joint. Most guys say, "Hell yes there is, you have to able to grease it!" I found out while farting around with lifted 4x4s with big tires and high torque, the grease fitting needs to be under compression. The grease fitting is a hole in the u joint, and if the driving yoke compresses that hole into the driven yoke they will suffer less failure. If the hole for the grease fitting is being pulled apart by the two yokes they bite the dust more often. Seems far fetched for your application, more like mud boggin with big tires. .02 A.G.
I don't know if anyone has mentioned it, but the U joints need to be in time with each other.
 

farmboy55

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Can you explain that please?
when you take a shaft apart such as a PTO shaft or drive shaft with U joints on each end. It has to be put back together so both U joints wrk together and not against each other. Try to explain better. They would in the same position on each end of the shaft. This pertains to a 2 peice shaft that slides in the middle. I've not wrked on your type of machine, so not sure of the type of shaft. dennis
 
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