AX-15 Sticky Gearbox

[MuchRespect]

Hi everyone,

 

Just got my 90 Renix 4.0 4x4 back from the mechanic yesterday after putting in a new ECM, master cylinder, crank sensor and fuel pressure regulator.

Was running and shifting great for about a day or so but this morning it began to give me issues placing in 1st and 2nd gear. I first noticed it going from neutral back into 1st when stopped and then it became more and more "sticky" shifting between 1st and 2nd. Eventually it became quite hard to push it into gear at all. When I finally parked, it wouldn't shift into reverse and began a light grind when I tried to force it. I restarted the motor which allowed me to force it into reverse.

 

Any ideas of what this could indicate or how to fix?
 

Appreciate the help

[Knucklehead97]

I say he didn't bleed the clutch MC good enough. I always gravity bleed mine, where you just let the fluid drip from the bleeder valve for about half an hour (watch the fluidlevel in the reservoir though)

[johnj92131]

Check the fluid level in your clutch master cylinder.  Bet it is low and you have air in the clutch line.  Solution is to bleed the clutch master and slave cylinder.  As Knucklehead said: watch the fluid level in the reservoir.  Top it off every couple of pumps on the clutch so you don't let more air in the clutch system.

[cruiser54]

Did he replace the brake master cylinder or clutch master cylinder?

 

Either way, with the vehicle off and stationary, AFTER checking and topping off the clutch master cylinder as needed, pump the clutch pedal about 30 times and leave it sit for 10 minutes. 

 

 

[MuchRespect]

Thanks guys! He replaced the clutch master cylinder. Is there another post with a step-by-step on how to do this?

Again, thanks for your patience on my noobery.

[MuchRespect]

On 5/4/2018 at 4:39 AM, cruiser54 said:

Did he replace the brake master cylinder or clutch master cylinder?

 

Either way, with the vehicle off and stationary, AFTER checking and topping off the clutch master cylinder as needed, pump the clutch pedal about 30 times and leave it sit for 10 minutes. 

 

 

So to clarify, the clutch master was the one replaced. I checked the reservoir and it remains between the min and max lines. Pumped the clutch 30 times and let sit for 10. Didn't seem to mitigate the issue. Still sticky. I'm very new to the truck so not sure if I misunderstood the suggestion. Noob questions:

 

Was I meant to bleed it first? Can I bleed it while it's in the truck or do I have to bench bleed?

 

Thanks for all the help

[DirtyComanche]

Did your mechanic do anything with the clutch?  I'm assuming he changed the brake master cylinder, not the clutch master cylinder?

 

You can (and basically have to) bleed the clutch with it installed.  There's a line with a bleeder screw on it coming out of the bellhousing where the pressure line goes in.  The procedure is to top up the master (you can even leave a fresh bottle of brake fluid upside down in it, just make sure it doesn't spill), then with a helper have them crack the bleed screw AS the clutch pedal is depressed, closing it when the pedal reaches the floor.  No, I have no idea why a clutch is bled that way, although I've had good luck doing it the incorrect way like one would bleed brakes (push pedal down, jam it in place, scoot under truck and crack the bleed screw, close it after the fluid squirts out).

 

Another thing to check is that the bushings in the clutch pedal are tight, and that the carpet and underlay isn't stopping you from getting full pedal travel.  You really do need nearly full travel to disengage the clutch on these trucks.

[MuchRespect]

Thanks for the info! And the step-by-step, he definitely replaced the clutch master, not the brake master. Will try this method for bleeding this week. Checked the bushings and the carpet, all seems to be in order.

 

Thanks again

[MuchRespect]

 

On 5/7/2018 at 11:45 PM, DirtyComanche said:

Did your mechanic do anything with the clutch?  I'm assuming he changed the brake master cylinder, not the clutch master cylinder?

 

You can (and basically have to) bleed the clutch with it installed.  There's a line with a bleeder screw on it coming out of the bellhousing where the pressure line goes in.  The procedure is to top up the master (you can even leave a fresh bottle of brake fluid upside down in it, just make sure it doesn't spill), then with a helper have them crack the bleed screw AS the clutch pedal is depressed, closing it when the pedal reaches the floor.  No, I have no idea why a clutch is bled that way, although I've had good luck doing it the incorrect way like one would bleed brakes (push pedal down, jam it in place, scoot under truck and crack the bleed screw, close it after the fluid squirts out).

 

Another thing to check is that the bushings in the clutch pedal are tight, and that the carpet and underlay isn't stopping you from getting full pedal travel.  You really do need nearly full travel to disengage the clutch on these trucks.

 

So I made an attempt at this today and didn't have a partner. I tried your solo hack using my club and found that when I opened the valve only a tiny bit of fluid/air came out. When took the club off and let the clutch out -- the fluid ran freely through the system air/fluid so I kind of assumed I had misunderstood your instructions and went along with it. I checked the reservoir and made sure it was stayed topped off. When no more air was coming out of the system, I closed the bleeder screw. Waited about thirty minutes and around the block and it was doing well if not better than before. Then on a second drive, the clutch sort of died on me. I lost almost entire pressure. I had to pump it at every stop light to even get it into gear. Barely made it home.

 

Just about everyone I've spoken to and every tutorial I've read suggests that fluid should only flow when the clutch is depressed and not when it's left out. Is that correct? And if so, what does it mean if my system drains freely when the clutch is let out?

 

Thanks again

[Eagle]

2 hours ago, MuchRespect said:

 

Just about everyone I've spoken to and every tutorial I've read suggests that fluid should only flow when the clutch is depressed and not when it's left out. Is that correct? And if so, what does it mean if my system drains freely when the clutch is let out?

 

Thanks again

 

I think you are still misunderstanding.

 

The clutch system, like the brake system, is a hydraulic system. It works by pushing fluid from the master cylinder to the slave cylinder under pressure. Once the moving column of fluid gets to the slave cylinder, it then pushes the pistol inside the slave, and that's what pushes on the clutch to disengage it.

 

Fluid does not compress under pressure -- so stepping on the peddle pushes a column of fluid through the clutch line. Air compresses, so if you have ANY air bubbles trapped in the line -- anywhere -- stepping on the clutch peddle only compresses the air bubble(s), it doesn't move the pistol in the slave cylinder. So ... we need to bleed the system to get the air out.

 

If you just open the bleeder screw without moving the peddle, fluid will drip out. This is called gravity bleeding. Some people have decent results gravity bleeding brakes -- I've never had good luck with it. The hydraulic clutch seems to be more difficult to get bled well, so it's important to do it right. And to do it right, you need an assistant. Your assistant sits in the driver's seat to work the peddle. You get underneath to work the bleeder screw. It doesn't mean to depress the peddle with a stick and leave it down while you open the bleeder screw.

 

When you are ready, have your helper SLOWLY pump the peddle up and down about three strokes while the bleeder is CLOSED. Did I say SLOWLY? Do it fast and any air in the system gets frothy -- if that happens, you'll never get it out. SLOWLY up and down for three strokes. Them, with the peddle up, you open the bleeder and tell your helper to depress the peddle. He pushes it down, SLOWLY but firmly. When it bottoms out, he holds it DOWN and tells you "DOWN." You close the bleeder.

 

Your helper then releases the peddle, and repeats the process of depressing the peddle SLOWLY for three strokes. At the end of the third, he lets the peddle up , tells you he's ready, and you open the bleeder. Once the bleeder is open, the helper again pushes the peddle down, slowly and firmly, until it bottoms out. Then he holds it down, tells you it's down, and you close the bleeder.

 

You keep repeating this process until you get no air from the bleeder, and only clean fluid. One of you has to check the master cylinder after every cycle or every other cycle to make certain there's fluid in the reservoir. If you let it get pumped out, you'll let air in and then you have to start over.

[MuchRespect]

13 minutes ago, Eagle said:

 

I think you are still misunderstanding.

 

The clutch system, like the brake system, is a hydraulic system. It works by pushing fluid from the master cylinder to the slave cylinder under pressure. Once the moving column of fluid gets to the slave cylinder, it then pushes the pistol inside the slave, and that's what pushes on the clutch to disengage it.

 

Fluid does not compress under pressure -- so stepping on the peddle pushes a column of fluid through the clutch line. Air compresses, so if you have ANY air bubbles trapped in the line -- anywhere -- stepping on the clutch peddle only compresses the air bubble(s), it doesn't move the pistol in the slave cylinder. So ... we need to bleed the system to get the air out.

 

If you just open the bleeder screw without moving the peddle, fluid will drip out. This is called gravity bleeding. Some people have decent results gravity bleeding brakes -- I've never had good luck with it. The hydraulic clutch seems to be more difficult to get bled well, so it's important to do it right. And to do it right, you need an assistant. Your assistant sits in the driver's seat to work the peddle. You get underneath to work the bleeder screw. It doesn't mean to depress the peddle with a stick and leave it down while you open the bleeder screw.

 

When you are ready, have your helper SLOWLY pump the peddle up and down about three strokes while the bleeder is CLOSED. Did I say SLOWLY? Do it fast and any air in the system gets frothy -- if that happens, you'll never get it out. SLOWLY up and down for three strokes. Them, with the peddle up, you open the bleeder and tell your helper to depress the peddle. He pushes it down, SLOWLY but firmly. When it bottoms out, he holds it DOWN and tells you "DOWN." You close the bleeder.

 

Your helper then releases the peddle, and repeats the process of depressing the peddle SLOWLY for three strokes. At the end of the third, he lets the peddle up , tells you he's ready, and you open the bleeder. Once the bleeder is open, the helper again pushes the peddle down, slowly and firmly, until it bottoms out. Then he holds it down, tells you it's down, and you close the bleeder.

 

You keep repeating this process until you get no air from the bleeder, and only clean fluid. One of you has to check the master cylinder after every cycle or every other cycle to make certain there's fluid in the reservoir. If you let it get pumped out, you'll let air in and then you have to start over.

 

A huge thank you for the comprehensive break down. I suppose I understood some of this in theory but only in bits and pieces. Been trying a stick for fifteen years and never had to bleed a clutch before. I appreciate your patience with my questions and willingness to break it down so thoroughly. Will try this tomorrow.

[crumbscomanche]

1 hour ago, Eagle said:

 

I think you are still misunderstanding.

 

The clutch system, like the brake system, is a hydraulic system. It works by pushing fluid from the master cylinder to the slave cylinder under pressure. Once the moving column of fluid gets to the slave cylinder, it then pushes the pistol inside the slave, and that's what pushes on the clutch to disengage it.

 

Fluid does not compress under pressure -- so stepping on the peddle pushes a column of fluid through the clutch line. Air compresses, so if you have ANY air bubbles trapped in the line -- anywhere -- stepping on the clutch peddle only compresses the air bubble(s), it doesn't move the pistol in the slave cylinder. So ... we need to bleed the system to get the air out.

 

If you just open the bleeder screw without moving the peddle, fluid will drip out. This is called gravity bleeding. Some people have decent results gravity bleeding brakes -- I've never had good luck with it. The hydraulic clutch seems to be more difficult to get bled well, so it's important to do it right. And to do it right, you need an assistant. Your assistant sits in the driver's seat to work the peddle. You get underneath to work the bleeder screw. It doesn't mean to depress the peddle with a stick and leave it down while you open the bleeder screw.

 

When you are ready, have your helper SLOWLY pump the peddle up and down about three strokes while the bleeder is CLOSED. Did I say SLOWLY? Do it fast and any air in the system gets frothy -- if that happens, you'll never get it out. SLOWLY up and down for three strokes. Them, with the peddle up, you open the bleeder and tell your helper to depress the peddle. He pushes it down, SLOWLY but firmly. When it bottoms out, he holds it DOWN and tells you "DOWN." You close the bleeder.

 

Your helper then releases the peddle, and repeats the process of depressing the peddle SLOWLY for three strokes. At the end of the third, he lets the peddle up , tells you he's ready, and you open the bleeder. Once the bleeder is open, the helper again pushes the peddle down, slowly and firmly, until it bottoms out. Then he holds it down, tells you it's down, and you close the bleeder.

 

You keep repeating this process until you get no air from the bleeder, and only clean fluid. One of you has to check the master cylinder after every cycle or every other cycle to make certain there's fluid in the reservoir. If you let it get pumped out, you'll let air in and then you have to start over.

This is a great