Biscuit is (still) Keeping The FJ40 - Customization/Improvement Thread (7 Viewers)

[Biscuit]

Next up to address is the clutch.
It's slipping under moderate or heavy acceleration. The clutch disc is at least 20 years old. Currently I have the three-finger 3speed clutch with the 3-speed flywheel in front of my H42 4-speed. (Coincidentally period correct for my 1974 had it come with the 4-speed). There is a good enough local shop, that I'm probably going to throw money at the problem. The big question is do I update to the later clutch or just replace the old-style three finger.

That will be followed shortly by rear brakes.
The existing drum brakes need work. Like the front, if I am going to put a bunch of new parts in, I don't want manually adjusted brakes. Options: Rear disc kit with the GM components (likely easiest). Though I have seen a thread with @cruisermatt FJ60 rear drum conversion (would require sorting out the parking brake to enable the self adjusting). This one I can do in my driveway.

 

[65swb45]

I still have some Aisin clutch kits for the older systems Mike. But know that the throwout bearing hubs are obsolete, and they are a high wear item.
I have put some of them aside to see how they take to welding up the divots, but haven’t gotten around to trying it yet. If you need one of those as well, lmk, and I will move that project up the list.
OTOH, if your wheeling days are over, changing to the newer design will net you a more highway friendly clutch. I just got one of those flywheels turned on Thursday

 

[Biscuit]

Had a hunch on the clutch slipping and decided to check it out.

My clutch pedal has always been lower (closer to the sloped part of the floor) than the brake. I hadn't thought much of it. So I decide to go check the pedal height, play, and clutch fork play and compare them to the FSM.

Pedal had zero play. Height was far below spec. Spec is 215mm, this was probably closer to 180mm. (I didn't measure before).

Without adjusting the pedal, I checked the fork play. Also zero.

Started off with adjusting the pedal. FSM spec with the booster is 215mm pedal height and 0.5-3mm of play. With the clutch pedal at 215mm it was even with the brake pedal (shocking, I know). Play was now between 15mm and 20mm.

Now that I had play in the pedal, I went back under the truck and rechecked the play on the fork. 3mm, right on spec. (Better lucky than good in this case).

Now that the clutch hydraulics are fully releasing pressure, I took the 40 for few drives. First around the neighboor hood and the a longer one when it was warm. Clutch definitely is engaging much better.

Since the pedal still has a lot of excess play I can in the immediate short term, adjust the pedal back down until the play is in spec. But master cylinder probably needs to be rebuilt. I suspect the spring in there has been compressed for a very long time and isn't fully expanding.

I still need to drive the 40 in similar conditions to when I had the slip symptoms to see how it performs.

 

[pb4ugo]

Are you running a return spring on the clutch fork? The piston in the slave needs to be seated all the way in the back of its bore. You might try bleeding the system. There's no reason to have 15-20mm of freeplay if measured correctly. I found the freeplay is when the piston/rod in the slave starts move. My slave is on the drivers side so i can look at the slave and push the pedal with my hand.

 

[Biscuit]

I do have the return spring. Replaced it and the bracket for it about a year ago along with the push rod. It's definitely seated all the way into the slave cylinder.

 

[pb4ugo]

Is your 15 to 20mm measurement when you feel resistance in the pedsl because of the t/o bearing pushing against the pp? Not that it matters, the freeplay adjustment is to insure the master isnt pushing fluid with the pedal rest.

 

[65swb45]

Mike, you need to have someone push down on the pedal while you carefully watch the clutch fork. The fork should pivot cleanly, like a tie rod end. Unfortunately it is not uncommon for the rivets that hold the spring steel pivot clip to the pivot to loosen up. Then the fork lifts off the pivot before actually moving the throwout bearing.

If this is the case, and the clip is not too loose, you can remove the fork and re-peen the rivets. Or you can replace them with an appropriate gauge of sheet metal screw.

 

[Biscuit]

Mike, you need to have someone push down on the pedal while you carefully watch the clutch fork. The fork should pivot cleanly, like a tie rod end. Unfortunately it is not uncommon for the rivets that hold the spring steel pivot clip to the pivot to loosen up.

If this is the case, and the clip is not too loose, you can remove the fork and re-peen the rivets. Or you can replace them with an appropriate gauge of sheet metal screw.

I'll give that a look next weekend.

Is your 15 to 20mm measurement when you feel resistance in the pedsl because of the t/o bearing pushing against the pp? Not that it matters, the freeplay adjustment is to insure the master isnt pushing fluid with the pedal rest.

15mm to 20mm was for any resistance beyond the pedal return spring force. Felt like that is when the pedal push rod was engaging the master cylinder piston. Looking at the pedal pushrod I can adjust it maybe 5mm to have acceptable thread engagement left. Still far beyond spec.