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621 Cat Scraper

621 Cat Scraper

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Travis D
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I have a 621 cat scraper with a slipping transmission. It pulls fine in all gears until in is used for an hour or two, then the transmission gets hot and if it is shifted will only engage in first and reverse gears. After it is shut off and cools (overnight) it pulls fine until it again gets hot. I have changed the transmission fluid and filter, oil and filter looked good. I think the transmission is over heating, does anyone know how the transmission is cooled and what I need to do to fix it?
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Wed, Jan 20, 2016 7:35 AM
Old Magnet
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What's the s/n of the machine? We don't get much traffic here on 621's but there are the basic things to be checked before it gets complicated. I don't know very much about them but I do have the information for testing and adjusting the power shift transmission.Maybe we can team up with some one that can provide more knowledge.
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Wed, Jan 20, 2016 8:26 AM
Travis D
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Reply to Old Magnet:
What's the s/n of the machine? We don't get much traffic here on 621's but there are the basic things to be checked before it gets complicated. I don't know very much about them but I do have the information for testing and adjusting the power shift transmission.Maybe we can team up with some one that can provide more knowledge.
thanks, I will get it and let you know
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Wed, Jan 20, 2016 8:43 AM
Rome K/G
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Reply to Old Magnet:
What's the s/n of the machine? We don't get much traffic here on 621's but there are the basic things to be checked before it gets complicated. I don't know very much about them but I do have the information for testing and adjusting the power shift transmission.Maybe we can team up with some one that can provide more knowledge.
Go through and check all the simple things first, oil (is it really dark or black), filters(cut open n inspect for metal), screens, pump pressure, transmission valve control spool (broken springs), before tearing down trans.
Gary
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Wed, Jan 20, 2016 8:46 AM
Rome K/G
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Reply to Rome K/G:
Go through and check all the simple things first, oil (is it really dark or black), filters(cut open n inspect for metal), screens, pump pressure, transmission valve control spool (broken springs), before tearing down trans.
Gary
May be the modulating relief valve spring, but not sure on the overheating problem.
Gary
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Wed, Jan 20, 2016 8:48 AM
Hillbillybjopkr
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Reply to Rome K/G:
May be the modulating relief valve spring, but not sure on the overheating problem.
Gary
its funny....I ran 621b for a few yrs when I was younger.....ran a lot of different scrapers in my younger yrs......sounds like something is slipping and producing a lot of heat.....worthless info I'm sure...but just a thought...
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Wed, Jan 20, 2016 11:42 AM
rmyram
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you need to check transmission pressures, something is leaking causing the oil to heat, after the oil warms up you are losing pressure which is causing the slippage an the gear restrictions and or losses.

stop running the unit before you cause uneccessary damage, the symptoms are indicating that you are having a failure, continued use will make the repairs much more costly.
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Wed, Jan 20, 2016 11:12 PM
Old Magnet
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Reply to rmyram:
you need to check transmission pressures, something is leaking causing the oil to heat, after the oil warms up you are losing pressure which is causing the slippage an the gear restrictions and or losses.

stop running the unit before you cause uneccessary damage, the symptoms are indicating that you are having a failure, continued use will make the repairs much more costly.
Until I can have the model s/n it appears they have a transmission and retarder oil cooler. First order would be to check the cooling system, radiator, air flow, thermostats, piping, oil cooler by-pass valve, cooler inlet/outlet temperatures, flow, etc. One of those cheap infra-red hand held thermometers is going to be a necessity.
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Thu, Jan 21, 2016 12:31 AM
Rome K/G
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Reply to Old Magnet:
Until I can have the model s/n it appears they have a transmission and retarder oil cooler. First order would be to check the cooling system, radiator, air flow, thermostats, piping, oil cooler by-pass valve, cooler inlet/outlet temperatures, flow, etc. One of those cheap infra-red hand held thermometers is going to be a necessity.
With ya there to Mag.
Gary
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Thu, Jan 21, 2016 1:11 AM
old-iron-habit
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Reply to Rome K/G:
With ya there to Mag.
Gary
I read this post on another forum and one of the comments from the poster said that after a while they could not load in higher gears. Is it normal to load in anything higher than low? I would think a higher gear would cause converter slippage and heat. Comments?
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Thu, Jan 21, 2016 1:27 AM
catsilver
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Reply to old-iron-habit:
I read this post on another forum and one of the comments from the poster said that after a while they could not load in higher gears. Is it normal to load in anything higher than low? I would think a higher gear would cause converter slippage and heat. Comments?
The first thing to do on this semi-auto transmission is to carry out a full pressure check, first gear is torque drive, 2nd is torque to start off with then locks into direct as speed increases, if clutch pressure is being lost, it will not lock up and change up to higher gears.
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Thu, Jan 21, 2016 3:39 AM
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