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Final Drive Motor on One Side Bogging Down Engine - Cat 304cr

Howey Matt

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Dec 19, 2021
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128
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Howey in the Hills, FL
I just replaced both final drives on this machine. It solved my issue on one side (caused by a failed final drive) but I'm still having a problem with the other side.

Basically, when I engage the final drive on that side, the engine bogs down and the hydraulic pump whines like it's under strain. The final drive does turn, but not as fast as the other side. It's a brand new final drive, and the old final drive did the same thing, so I'm wondering what to look at to figure this out. I have a parts manual, owner's manual, and service manual - I'm just not sure where to start.

Any troubleshooting steps or help would be greatly appreciated. It's a 2004 Cat 304cr (NAD00987). Thanks!
 

1466IH

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Feb 4, 2014
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613
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prairie du rocher, il
I don't have my computer near me to look up specifics but it sounds like the brake isn't releasing. I would imagine both sides are teed together but have seen them separate in the rotary manifold before
 

uffex

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Good day
A couple of possibilities - binding brake - failing bearing in the transmission, if one side required replacement there is a good chance the remaining drive is not far behind. Drain some lube for evidence of impending failure.
Kind regards
Uffex
 

Howey Matt

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Dec 19, 2021
Messages
128
Location
Howey in the Hills, FL
I don't have my computer near me to look up specifics but it sounds like the brake isn't releasing. I would imagine both sides are teed together but have seen them separate in the rotary manifold before

It looks like they each connect to different ports on the rotary manifold - no tees.

I'm wondering if it's a valve or something since the drive motor is brand new. I'm thinking I can do a pressure test on the hoses at the drive to see if the drive is getting adequate pressure or not. That would tell me if the problem is with the drive or something else.
 

Mobiltech

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Jan 14, 2014
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Sask.
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If there is a brake release hose and a 2 speed hose is there a chance you have them mixed up on the final drive motor?
Did the final drive come with the motor and brake as a unit ?
 

Howey Matt

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Dec 19, 2021
Messages
128
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Howey in the Hills, FL
If there is a brake release hose and a 2 speed hose is there a chance you have them mixed up on the final drive motor?
Did the final drive come with the motor and brake as a unit ?

Everything came as a unit - just bolt on and connect the hoses. I thought maybe I hooked the hoses up incorrectly, but I followed the instructions exactly (I even verified the case drain and two-speed lines). I installed both drives the same way and one of them is working. Also, the old drive had the same issue, so that would mean that one was installed incorrectly as well. I'm pretty sure it was the original drive.
 

1466IH

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Feb 4, 2014
Messages
613
Location
prairie du rocher, il
If there are separate brake ports on the rotary manifold you could have a blockage there. Try to put a gauge on that brake line somewhere and see what kind of pressure you are at.
 

Howey Matt

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Dec 19, 2021
Messages
128
Location
Howey in the Hills, FL
If there are separate brake ports on the rotary manifold you could have a blockage there. Try to put a gauge on that brake line somewhere and see what kind of pressure you are at.

Which line are you referring to when you say brake line? I have two large drive lines and two smaller hoses which are the case drain and the two speed. I thought the brake on these smaller machines was released when the pressure in the drive line increased. So, I'm assuming I need to test the pressure on the drive lines? If the drive is getting pressure and not releasing, it's the drive. If the drive is not getting pressure, it's something further up the line.
 

Howey Matt

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Dec 19, 2021
Messages
128
Location
Howey in the Hills, FL
I ordered a pressure test kit.

I'm leaning towards an issue with the swivel valve since both the drives are new. Any idea how to test the swivel valve? I went through the service manual but I don't see anything. I guess I'll just see if the swivel valve is getting pressure but not sending it to the drive.

Would bad seals in the swivel valve cause this issue?
 

1466IH

Senior Member
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Feb 4, 2014
Messages
613
Location
prairie du rocher, il
I will do my best to remember to grab my computer from the shop tomorrow and can do some more digging. Since it is loading up the engine you have a restriction somewhere. Could be any number of things but does not sound like a rotary manifold issue. Usually that leads to problems with both tracks not just one.
 

Tyler d4c

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Mar 2, 2016
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1,750
Location
Salix Pa
Time for a public service announcement
Final drives have oil
They need it
It's very important
Change regularly
That will be all
 

Nige

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Jun 22, 2011
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28,979
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G..G..G..Granville.........!! Fetch your cloth.
Is it possible to swap the main forward/reverse hydraulic connections of the LH & RH motors somewhere in the upper frame of the machine (before the swivel in other words) and see whether the problem changes sides.?
The 2-speed and case drain lines at the swivel are common.
 

Attachments

  • M0125928-02 - Hydraulic Schematic.pdf
    2.3 MB · Views: 11

Howey Matt

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Dec 19, 2021
Messages
128
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Howey in the Hills, FL
I'm getting around 3,800 psi on each of the large hoses (forward and reverse) at the drive motor. That should be adequate according to the service manual. Must be a problem with the brand new drive... I'm going to call the place I bought it from tomorrow. I really didn't think it would be an issue with the drive since it's brand new, but I would be the guy to get the defective one.
 

uffex

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Good day
Compliments on a sensible approach to troublee shooting.
Kind regards
Uffex
 

Howey Matt

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Dec 19, 2021
Messages
128
Location
Howey in the Hills, FL
UPDATE

The place I bought the drive motor from swears there's nothing wrong with the drive. They're saying they tested it before it was shipped and everything checked out.

I wasn't sure what else to do, so I removed the problem drive and hooked it to the hydraulic lines on the other side of the machine, and it works perfectly fine!

So, the drive is getting 3,800 psi and it works fine on the other side of the machine, but it barely turns and strains the hydraulic pump and engine on the side where it belongs. Any ideas as to what could be causing this?

When I say it strains the engine/pump, I mean it sounds like the hydraulic line is capped and the drive spins very slowly.
 

Vetech63

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Aug 10, 2016
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Oklahoma
Sounds like a main control valve problem. What failed on your original final? The hydraulic or mechanical side?
 

Howey Matt

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Dec 19, 2021
Messages
128
Location
Howey in the Hills, FL
Sounds like a main control valve problem. What failed on your original final? The hydraulic or mechanical side?

The drive on the other side failed mechanically. I decided to replace the drive on this side as well since it was having this problem. So, I guess one side mechanical, the other side hydraulic.

I’ve been going over the service manual and I located the port on the main control valve that controls the right drive motor. Any idea how to go about testing it?
 

uffex

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Good day
I suggest check the brake release pressure at the motor although its strange to release one side and not the other. Be sure that the case drain and brake release lines are not switched over.
Kind regards
Uffex
 

Nige

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G..G..G..Granville.........!! Fetch your cloth.
Be sure that the case drain and brake release lines are not switched over.
Kind regards
Uffex
See the hydraulic schematic I posted above. The two small external lines are for travel motor case drain and two-speed. There is no travel motor brake the way we understand it. Same comment still applies though - are the two lines somehow mixed up.?

I found another thread where the OP was asking about the location of the case drain & 2-speed lines at the swivel. I suggest that before going anywhere near the main hydraulic control valve the connections of those two lines between the swivel and the travel motor that is not performing need to be investigated. Also this comment in Post #2 from the OP above - "Also, two-speed does not seem to be working." It could be that a single cause is at the root of both problems.
https://www.heavyequipmentforums.co...dentifying-drive-motor-hydraulic-lines.95929/
 
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