Carraro TLB1 4WD noise and hard to shift

[Ivan Adiego]

Hi, I'm a new member on the forum. I've been reading some of the related threads, searched online and downloaded some manuals but still not really sure what is going on. I bought a used 2012 TEREX 760b backhoe with 2300 hours a couple of months ago, It came with a synchro shuttle transmission (manual shifter, 4 forward and 4 reverse). After a long journey to my little ranch in the middle of nowhere I started testing the machine. First, I noticed some sort of metallic slipping noise that gets louder as you rev up the engine, this occurs in neutral and all forward and reverse gears regardless if the clutch is engaged or not. And second, its hard to shift into gear or even between gears, sometimes really hard to the point that I'm worried that I might beak something if I don't wobble the shift lever a bit to persuade it to go into gear. At first I thought it might be a worn clutch but the sound does not change at all when it's in or out of gear or if I'm driving or not, so this might not be the case (I'm guessing). I was thinking that it could be something related to the gear synchronizer assembly but I'm not sure. I don't have internet access where the machine is sitting at right now, so I recorded a video that picks up the noise that it makes when I rev it up. any advise on what might be causing this will be really appreciated!

 

[JL Sargent]

Maybe somebody will come along that is familiar with that machine. I would start by getting the service manual and look for any good ideas there in sections that cover your transmission. Another idea would be to change the transmission/synchronizer oil and inspect the old oil for anything suspicious.

 

[Ivan Adiego]

Maybe somebody will come along that is familiar with that machine. I would start by getting the service manual and look for any good ideas there in sections that cover your transmission. Another idea would be to change the transmission/synchronizer oil and inspect the old oil for anything suspicious.

Changing the transmission oil is definitely on my list, I doubt the previous owner had changed it more than once. I'm also going to change the engine oil, hydraulic fluid and filters the next time I have time to work on the machine.

 

[Tinkerer]

Welcome to HEF, Ivan !
Does the tractor have a mechanical clutch and a shuttle shift ?
Hard shifting into and between gears is a classic example of a clutch not fully releasing.
That whining noise may not be related to the hard shifting.

 

[Ivan Adiego]

Welcome to HEF, Ivan !
Does the tractor have a mechanical clutch and a shuttle shift ?
Hard shifting into and between gears is a classic example of a clutch not fully releasing.
That whining noise may not be related to the hard shifting.

The forward and reverse clutches on this machine can be engaged with a lever (its electronic), neutral is in the middle (both disengaged). There are also electric disengage buttons that you can press either on the shift lever or the front loader joystick. As far as I know they are engaged by hydraulic pressure (attached pic). The clutch is disengaged by spring force when any of the previous buttons are pressed or the lever set to neutral. If the clutch was the problem it could be related to some plate broken or worn out. The hydraulic control unit above the transmission that controls the clutches could be missing oil something that would cause it not fully disengaging, testing the machine the sound does not change engaging or disengaging any of the clutches. I was thinking that if the machine is set to neutral and non of the other shafts/gears rotate (other than the primary shaft containing the clutch assembly), this would mean that the synchronizer unit is not the problem since it could not cause any noise because it actuates on other shaft that wouldn't be moving. If this is the case whatever is causing the problem would be between the torque converter and the clutch assembly, bearings don't seem a probable cause unless the transmission oil was trash (haven't checked it yet).

 

[Tinkerer]

I wish I could help you. Ivan.
But I don't know anything about your Terex.
I don't remember ever seeing a Terex T/L/B.

 

[alrman]

With the wheels raised off the ground, parkbrake off, engine running with FNR lever in neutral & 2nd gear engaged with manual shift - is there any drive being transferred to the rear wheels?

 

[Ivan Adiego]

As far as I can remenber the wheels did not spin while they where off the ground, but I never really payed atention to see if they moved or not. Probably havn't tested what you suggest since most of the times when the wheels whrere lifted was when I was trenching and probably had the manual shifter set to neutral. Next time I use the machine I'll test that and report the results back here!

 

[Ivan Adiego]

With the wheels raised off the ground, parkbrake off, engine running with FNR lever in neutral & 2nd gear engaged with manual shift - is there any drive being transferred to the rear wheels?

I think I found what could be causing all the problems, this machine has all the symptoms of a worn out transmission oil pump, and It' exactly between the clutch assembly and the torque converter. I'm sure that if I drain the transmission oil it would be black and the oil filter must be very clogged. The oil pump is driven by a different shaft, this would explain why the whining noise did not change regardless of the clutches being engaged or not. I remember that the noisiest place was near the torque converter, but at the time I didn't know the pump was there. I'll drain the oil, clean/replace the filters and pour new oil and see if the noise level decreases or if I'm able to shift into gear with less force, If that is the case the cause of the problems is certainly the oil pump. It was even stated in the manual!

 

[Ivan Adiego]

I wish I could help you. Ivan.
But I don't know anything about your Terex.
I don't remember ever seeing a Terex T/L/B.

I think I found the problem! I suspect is a bad oil pump caused by poorly maintained oil and transmission filters

 

[Tinkerer]

That is good news !
Keep us posted on your results.
Your experience will help others looking for help.

 

[Shay71]

Hello Ivan, how did you make out?
I just joined the group, I too have a Terex 760B (2009), my shifter is stiff, but no sounds like that, thank god.
I'm in Panama, parts are tough to find for this beast! But I love my old hoe, most days.

 

[Ivan Adiego]

Hello Ivan, how did you make out?
I just joined the group, I too have a Terex 760B (2009), my shifter is stiff, but no sounds like that, thank god.
I'm in Panama, parts are tough to find for this beast! But I love my old hoe, most days.

Welcome to the forum!
I created this thread 3 months ago but didn't have time to make the transmission oil and filter change in all this time! In fact I haven't even used the machine at all .So I can't tell you if my fix will work yet.
If you don't hear any noise, but the shifter is getting hard to shift, I think it could be related to the selector assembly not getting enough lubrication, this is what I think is happening in my case too. My suggestion would be to check the filters and change the transmission oil. The Carraro TLB1 transmissions that this machines use have a regular cartridge filter that you must replace with every oil change, but they also have a hidden mesh filter! This mesh filter is user serviceable so you don't need to replace it, but you do have to clean it every time the oil is changed. It is located at the very bottom of the transmission housing, look for a small oval shaped hatch that is held by two bolts (number 12 on the attached picture). After draining the transmission oil through the magnetic plug (number 13 on the attached picture), remove the bolts and the mesh filter should come out. check the magnetic plug to see if there's any metal shavings accumulated, hopefully there's none. This in my opinion this would be the easiest "fix" because it doesn't involve disassembling anything and if it works its also the cheap and fast to test out.
hopefully this can help you out!

 

[Shay71]

Hi Ivan, thanks for the detailed reply, yeah I did the transmission service a few months ago. The strainer was surprisingly clean, I didn't cut open the cartridge filter though. I have a feeling that the dowel pin in the short shaft is broken. The gear shift lever seems to rotate a bit. I'll get to tearing into one of these days.

 

[Ivan Adiego]

Update on the transmission oil condition:
I removed all the oil from the transmission and it looked really good, almost no metal dust or shavings at all. Even the filter was really clean. This confirms that the pump was not clogged at all, but instead it run dry at some point causing it to be damaged. Inspecting the filter mount revealed that it was rewelded to the chassis, indicating that it probably got nocked out at some point. This would explain why the gear pump of the transmission would have worn out that fast. About the hard shifting, it is probably due to the shift assembly is not receiving as much oil as it needs because of the worn out pump, or some damage when it run dry, but can't confirm that without taking apart the transmission.
Overall, the the transmission oil pump needs to be replaced, which is comparatively cheaper than fixing anything on the gearbox. But I still got to take apart the thole transmission unit to replace it, but I'll need to buy appropriate tools before taking on that job.

 

[Shay71]

Update on the transmission oil condition:
I removed all the oil from the transmission and it looked really good, almost no metal dust or shavings at all. Even the filter was really clean. This confirms that the pump was not clogged at all, but instead it run dry at some point causing it to be damaged. Inspecting the filter mount revealed that it was rewelded to the chassis, indicating that it probably got nocked out at some point. This would explain why the gear pump of the transmission would have worn out that fast. About the hard shifting, it is probably due to the shift assembly is not receiving as much oil as it needs because of the worn out pump, or some damage when it run dry, but can't confirm that without taking apart the transmission.
Overall, the the transmission oil pump needs to be replaced, which is comparatively cheaper than fixing anything on the gearbox. But I still got to take apart the thole transmission unit to replace it, but I'll need to buy appropriate tools before taking on that job.

Mine has had problems climbing hills in 3rd and 4th. It doesn't load down the engine as it should, so I've known it's slipping somewhere for a while. Although it still pushed good in 1st.
Today I put some gauges on it, almost 0 pressure on a 3000 psi gauge, should be around 1500psi.
I took apart the pressure regulator valve hoping to find some crap keeping it from building pressure. There are several pressure relief valves built into the valve assembly, but the others aren't accessible without pulling off the whole control valve assembly. I found a pump in Turkey; with the o ring and seal it's $350 US. I've ordered from them before, no problem.

I found a place in Latvia with all the pins and bushings. $850 for all of the bushings for the loader and hoe.

 

[Ivan Adiego]

Mine has had problems climbing hills in 3rd and 4th. It doesn't load down the engine as it should, so I've known it's slipping somewhere for a while. Although it still pushed good in 1st.
Today I put some gauges on it, almost 0 pressure on a 3000 psi gauge, should be around 1500psi.
I took apart the pressure regulator valve hoping to find some crap keeping it from building pressure. There are several pressure relief valves built into the valve assembly, but the others aren't accessible without pulling off the whole control valve assembly. I found a pump in Turkey; with the o ring and seal it's $350 US. I've ordered from them before, no problem.

I found a place in Latvia with all the pins and bushings. $850 for all of the bushings for the loader and hoe.

Where you testing the hydraulic pump pressure? I think that the clutches in the transmission use hydraulic pressure to engage and disengage. Mine also does not pull that much in 3rd and even less in 4rt gear, but once it gets going and the torque converter stops slipping it runs just fine. Here I found in one service manual how to test the transmission oil pump pressure too. Based on the location of the oil filter I might have the other model that is secured to the chassis instead of this one:

 

[Shay71]

Hi Ivan, once I used a 0-400psi gauge I got good readings. Clutch pressures are 175psi. Which is good. I checked all pressures and they are within range.
When I changed oil last time I made a mistake. I saw the Allison C-4 on ATF fluid and used it. I found the grade should be sae 30 oil. So I checked and found the viscosity of sae 30 is 9.3 at 100deg C. ATF is around 7.
So I drained the transmission, only about 11 liters came out. 22 liter capacity.
I refilled with Universal Tractor Fluid which has the same viscosity of SAE 30.
I ran the engine for a few minutes,
Then I drained it again (11 litres) and discarded that. Then filled with UTF and 2 litres of SAE 50. That was based on a calculation I did in Excel.
I should be pretty close to the correct viscosity.
When I drained it, I cleaned the suction strainer. I found fibers in it, I assume that’s clutch material.

It climbs better in 3rd gear now, but I haven’t road tested it yet.

Carraro has some great videos on how to rebuild. Worth a watch. They show a procedure for the install of the shaft seals for the clutch pressure porting.
They heat the seals and have a special tool, a collar, to pre shape them to seal in the housing.
I saw a YouTube mechanic rebuild one, didn’t use the tool. And figured that the housing was worn and needed machining. I’m guessing he found out about the collar, but didn’t mention it in his video.

I have ordered a new filter, I’ll drain and check the suction strainer for fiber. I hope the clutches are ok in the end.
I’m guessing the ATF low viscosity allowed the torque converter to slip more than designed. Carraro torque ratio is 2.6:1, but Terex changed it to at 3:1 in their design. The torque converter does not have a lock up clutch,FYI.
The ATF low viscosity may have resulted in lower clutch pressure, hence the fiber in the suction strainer.
Time will tell.

There is a good source of Carraro parts out of Turkey. About 1/3 the price.
And I found a place in Latvia that sells pins and bushings for the boom and bucket pivots. About 1/3 of the price as well.
She’s an old hoe, but I love her.

 

[Ivan Adiego]

Hi Ivan, once I used a 0-400psi gauge I got good readings. Clutch pressures are 175psi. Which is good. I checked all pressures and they are within range.
When I changed oil last time I made a mistake. I saw the Allison C-4 on ATF fluid and used it. I found the grade should be sae 30 oil. So I checked and found the viscosity of sae 30 is 9.3 at 100deg C. ATF is around 7.
So I drained the transmission, only about 11 liters came out. 22 liter capacity.
I refilled with Universal Tractor Fluid which has the same viscosity of SAE 30.
I ran the engine for a few minutes,
Then I drained it again (11 litres) and discarded that. Then filled with UTF and 2 litres of SAE 50. That was based on a calculation I did in Excel.
I should be pretty close to the correct viscosity.
When I drained it, I cleaned the suction strainer. I found fibers in it, I assume that’s clutch material.

It climbs better in 3rd gear now, but I haven’t road tested it yet.

Carraro has some great videos on how to rebuild. Worth a watch. They show a procedure for the install of the shaft seals for the clutch pressure porting.
They heat the seals and have a special tool, a collar, to pre shape them to seal in the housing.
I saw a YouTube mechanic rebuild one, didn’t use the tool. And figured that the housing was worn and needed machining. I’m guessing he found out about the collar, but didn’t mention it in his video.

I have ordered a new filter, I’ll drain and check the suction strainer for fiber. I hope the clutches are ok in the end.
I’m guessing the ATF low viscosity allowed the torque converter to slip more than designed. Carraro torque ratio is 2.6:1, but Terex changed it to at 3:1 in their design. The torque converter does not have a lock up clutch,FYI.
The ATF low viscosity may have resulted in lower clutch pressure, hence the fiber in the suction strainer.
Time will tell.

There is a good source of Carraro parts out of Turkey. About 1/3 the price.
And I found a place in Latvia that sells pins and bushings for the boom and bucket pivots. About 1/3 of the price as well.
She’s an old hoe, but I love her.

For the transmission oil i bought Shell Spirax S1 ATF TASA because I saw that its Suffix "A" type (like one of the suggested in the manual) , in the specification it's stated that is meant for "use as transmission oil in offroad machinery". I Didn't really check what the viscosity and density was before buying it. I haven't changed it yet since I know that the pump is already damaged and the oil it came with is almost new, but now i have the doubt if the previous owner might have used an incorrect transmission oil. So i might change it next time and see if it makes any difference.

 

[Shay71]

I too have noise from the transmission, but it’s from one of the the pressure regulators in the valve body on top. I took apart the main regulator and cleaned. The other is on the front side of the valve body and I can’t get a wrench on it. The floor frame is in the way.
Pumps seem to be a common failure, but might not be the case if the oil is too light.