Slipping clutch (1 Viewer)

[Spook50]

Openly admitting to my inexperience with working on and diagnosing manual tranny and clutch issues here, but any opportunity to learn something new....

Had a brand new LUK clutch installed when I had my 62 converted to an H55F in the spring of 2020. No issues aside from apparent wear on the 1/3 synchro as 3rd gear is a bit notchy at all temps (better when warm, as expected).

Lately though I've noticed my clutch slips periodically in in the cold, and doesn't engage until my pedal is almost completely out. First thing I did was follow the FSM procedure for adjusting the clevis on the master cylinder rod where it attaches to the pedal. It was tighter than it should've been, so I got it back to spec and that alleviated the issue but didn't eliminate it completely. My slave cylinder is the newer, non adjustable style. I have a habit of starting out in 2nd gear when on level roads, and though I don't drive too aggressively, I don't baby the clutch either. Would I be correct to think that this is far too soon for an OEM spec LUK clutch to be wearing out, or am I mistaken? When fully engaged, there's no problem. But when I put even a small amount of force on the pedal, it slips and disengages. Pedal force to fully actuate the clutch still feels firm and positive though. Next step is to pull the inspection cover and check for any signs of oil, which I don't expect to find since it does perform normally when warm (with the exception of course being the pedal travel issue).

Reading the FSM, it looks like the next steps involve actual removal of the clutch to fully inspect it, which I don't have the luxury of doing at this point, so I'm hoping to get some ideas of anything odd I might be missing that I can take a look at before going down that road.

 

[Godwin]

Ignore the FSM and readjust the clutch pedal until it feels right and hooks up where you want it. Play around with the adjustment at the extremes and go from there. The sweet spot will be somewhere in-between.

 

[cps432]

My clutch is very sensitive to pedal pressure too. It will engage with about 1/4” of travel. I’ve never had it slip or fail to engage, but occasionally I’ll miss a gear if I let off the clutch too soon. It’s a timing thing with shifting and doing the pedal dance. I haven’t messed with the adjustments since I installed the 5 speed. I just learned how to shift it like it is. Like I said, it’s a timing thing for me.

 

[OSS]

The normal clutch action on the FJ60 (using all Toyota parts) starts disengagement when the pedal is pushed in about an 0.5 to 1 inch. Everything happens right in the beginning. There’s lots of pedal throw after disengagement.

My last Toyota clutch disc I replaced after 220,000 miles and the disc was only 1/2 worn. Plenty of friction material left. (I had to replace the pilot bearing so I replaced everything while I was in there). Obviously I’m gentle on the clutch since the disc probably would have gone 500,000 miles.

Its hard to believe that your new clutch is worn out. You’d have to be dragging it all the time — though I did speak to a transmission tech eons ago and he said he’s seen brand new clutches wear out in a couple months when driven by “teenagers “.
Obviously they weren’t driving land cruisers, but how a clutch is used obviously will determine its life span.

When I accidentally got a little grease on my first clutch disc (from applying too much grease to the input shaft splines) the clutch juddered when engaging, but once engaged it didn’t slip.

Even if a clutch disc is on its last millimeter of friction material, it shouldn’t slip.
Slippage is caused by:

Glazed flywheel
Weak clutch cover springs
Glazed clutch cover friction surface
Glazed clutch disc
Incorrect adjustment where throw out bearing isn’t releasing pressure.

Glazing a clutch disc takes some real concentrated effort. You’d smell it burning before it glazes over - if it ever did.
I’m thinking that if your clutch parts aren’t Toyota (Aisin), that could be the problem.

 

[Spook50]

The normal clutch action on the FJ60 (using all Toyota parts) starts disengagement when the pedal is pushed in about an 0.5 to 1 inch. Everything happens right in the beginning. There’s lots of pedal throw after disengagement.

My last Toyota clutch disc I replaced after 220,000 miles and the disc was only 1/2 worn. Plenty of friction material left. (I had to replace the pilot bearing so I replaced everything while I was in there). Obviously I’m gentle on the clutch since the disc probably would have gone 500,000 miles.

Its hard to believe that your new clutch is worn out. You’d have to be dragging it all the time — though I did speak to a transmission tech eons ago and he said he’s seen brand new clutches wear out in a couple months when driven by “teenagers “.
Obviously they weren’t driving land cruisers, but how a clutch is used obviously will determine its life span.

When I accidentally got a little grease on my first clutch disc (from applying too much grease to the input shaft splines) the clutch juddered when engaging, but once engaged it didn’t slip.

Even if a clutch disc is on its last millimeter of friction material, it shouldn’t slip.
Slippage is caused by:

Glazed flywheel
Weak clutch cover springs
Glazed clutch cover friction surface
Glazed clutch disc
Incorrect adjustment where throw out bearing isn’t releasing pressure.

Glazing a clutch disc takes some real concentrated effort. You’d smell it burning before it glazes over - if it ever did.
I’m thinking that if your clutch parts aren’t Toyota (Aisin), that could be the problem.

Great info here. I have no reason to think any components are glazed, luckily. There were a couple points between this last summer and summer of '21 that I smelled a hot clutch after having to really get on it to get moving out of a commercial truck's way (him bigger than me ), though briefly and only when I had my windows open, and the clutch operated just fine long afterwards.

Given what you described for oil/grease contamination I'm even less expectant to see anything on my clutch when I go take a look at it. Only time I've gotten any kind of shuddering are from my engine on the rare occasion I upshift too early.

The clutch is a LUK that was installed new in 2020, which I decided to use after reading some caveats of going with a Centerforce and then seeing that LUK is often used by Toyota dealers for clutch jobs.

To what @Godwin suggested, my pedal is adjusted with about 2mm of gap before engaging the master cylinder push rod, so I should say the clutch disengages almost immediately in push rod travel. Soon as I go back outside I'll check just how much pedal movement I have before the clutch disengages. Knowing that the clutch does normally disengage early on in pedal travel, I would say that even with the pedal adjusted properly, it's happening in maybe half the travel that I had over this last summer and has steadily decreased since.

Edit: My brother in law stopped by so I had him help me check out the clutch. Everything underneath looked good. Dust, but bone dry and there's about 5-6mm of friction material still there. No obvious damage or anything out of place, and the action of the clutch itself looked just fine. I was reminded that I need a fork boot though, so that'll be ordered hopefully soon. At a bit of a loss for what to look for next.