Mixing clutch slave parts from different years (2 Viewers)

[hobbes]

When I'm driving my clutch release point seems to move around occasionally. This most often occurs on first start of the day, but not always. First thought was a bleed problem since pumping the clutch fixes it, but bleeding it doesn't seem to help. My truck has gone through three engine iterations (74 1.5F, 75 2F, and 87 2F) so is a bit of a mashup of parts. The clutch, fork and slave are new (and for a '75+ truck). But the adjustment nut on the end of the rod is all the way out. I've got the pre '75 spring, etc on the slave. The throwout bearing is definitely not engaged, so I don't think its a mis-adjustment. The clutch pedal is adjusted to factory specs. 95% of the time everything works perfect and releases where it should. So my question is if my slave is too far away from the clutch fork? Should I buy a '75+ rear motor mount and slave return spring? Do those move the slave closer to the fork? Maybe the slave rod isn't returning consistently enough sometimes to get a full stroke? (and I see my slave has rotated a bit on me, so I'll fix that)

Thanks.

 

[middlecalf]

Maybe related, or not, but what do your other engine mounts look like?

 

[B y r o n]

Does the clutch work when things are cold but stop working when things are warmed up? If so the fluid could be too close to the exhaust and boiling in the line. Boiling causes air so no clutch.

 

[hobbes]

Maybe related, or not, but what do your other engine mounts look like?

Good question. Fronts are brand new. The rears are original to a ‘74 and hard pucks. I do need to replace them.

 

[hobbes]

Does the clutch work when things are cold but stop working when things are warmed up? If so the fluid could be too close to the exhaust and boiling in the line. Boiling causes air so no clutch.

No. The clutch works fine when hot. Temperatures have no effect. Prior to my current 3FE header setup, I had 2F headers. Same issue.

 

[bikersmurf]

I’d replace the tired flex line with a braided SS one.

Do you have a pedal return spring on the clutch pedal?

 

[hobbes]

Yes. The pedal has a return spring. The pedal height is adjusted to the maintenance manual. A new clutch line is on “the list”. I’ll have to scratch my head on that a bit as I’ve got a ‘76 body now. The lines run a bit different between the years.

And to be clear, my issue is every once in awhile the clutch will grab a few inches off the floor as I release it instead of its normal 3/4s way up. Seems like a couple pumps and it’s good to go. And it’s only once in a while.

 

[rkymtnflyfisher]

Sounds to me like the master is going out, I double pumped mine for a year or so.

It was worse in cold weather.


Is your fluid clear as it should be?

Start your rig, push in the clutch and hold it down, put it in first gear, keep the pedal down, see if the clutch catches after a few seconds.

Let us know.

 

[hobbes]

The truck sat for 10 years. It had a new generic master put on right before it sat. So it has a decade of sitting and low miles on it. The fluid is completely clear. I was leaning away from that since it isn't leaking, but a new master is certainly easy enough. Also, I think the issue predates the master (but that could have been the slave which is now new).

If I do the master, I'll obviously want to do the line as well. Are there braided SS lines already out there? If not, I'll just go OEM from CityRacer and do the rear engine mounts as well. (And I'll need to figure out how the '76 lines were run and bounce that off my '74 setup in the '76 body).

 

[FJ40Jim]

Which clutch is currently installed: Coil spring or diaphragm style?

 

[73FJ40]

It looks like your slave cylinder is on the driver's side. I suggest you identify all the components from the MC to the fly wheel. I'd be interested in which version of the throw out arm pivot point you're using..

 

[hobbes]

Current parts:
5/1974 FJ40 frame (and majority of parts). 8/1974 was a cutover to the newer stuff, so I have a "early" '74 FJ40.
1976 FJ40 tub.
1975 bell housing.
1974 generic parts store clutch master. 10 years old, low miles.
Early ’74 original hard line.
Early ‘74 original soft line.
1974-1980 new Aisin slave cylinder (Rock Auto defined years).
1975-1987 new Aisin clutch disk and pressure plate (Rock Auto defined years).
8/1974-07/1980 new OEM clutch fork (31204-60020).
8/1974-07/1980 new OEM fork release ball (pivot) (31236-60020).

Mounting brackets and springs are all pre 8/1974.

I am fairly certain the rear passenger side engine mount is 1975 (it is the same blue as a 1975 2F I had in there for years). The driver's side engine mount, I'm unsure if it is a early/1974 or 1975. I did that engine swap almost 20 years ago and cannot recall. But since the slave is already mounted there, I don't think it matters.

Everything is mounted on the US driver’s side. As you can see in the second photo below, the hard line is not clamped to the body due to the clamp tab being moved to the passenger’s side by 1976. A new Aisin master, OEM hard and soft lines are still available for early '74 FJ40s. If I had to move to the pax side, I'd think I'd need a hard line (NLA), new return spring and spring plate (NLA). I'd like to not have to change sides on the slave unless I have to (hard line being probably hardest to source).

 

[MoCoNative]

I had a brand new OEM clutch master puke it guts out while sitting for about a year or so. It was pricey, really made me mad a new master would spontaneously dump its fluid inside the cab and ruin the paint on the firewall. It just happened sitting, unused.

So a 10 year old generic, could be faulty. Had a generic brake master on my FJ60 die after a year too. Put a NAPA rebuild kit in, and it has been good to go. Might try a quick rebuild kit.

 

[hobbes]

Do clutch masters fail without leaking? I’ve only known them to fail by leaking fluid out.

A new Aisin is under $50, so no big deal for me to swap. But “while I’m there” will necessitate new lines. If my current “design” should work, then great.

 

[rkymtnflyfisher]

Yes

 

[rkymtnflyfisher]

Mine seemed to slowly bleed the pressure off, never had a leak.

 

[bikersmurf]

Yes, SS lines are out there. Mine was made by the local hydraulic shop... more than 20 years later it looks and works like new. I like that it doesn’t flex and all the pressure creates fork movement.

 

[FJ40Jim]

Current parts:
5/1974 FJ40 frame (and majority of parts). 8/1974 was a cutover to the newer stuff, so I have a "early" '74 FJ40.
1976 FJ40 tub.
1975 bell housing.
1974 generic parts store clutch master. 10 years old, low miles.
Early ’74 original hard line.
Early ‘74 original soft line.
1974-1980 new Aisin slave cylinder (Rock Auto defined years).
1975-1987 new Aisin clutch disk and pressure plate (Rock Auto defined years).
8/1974-07/1980 new OEM clutch fork (31204-60020).
8/1974-07/1980 new OEM fork release ball (pivot) (31236-60020).

Mounting brackets and springs are all pre 8/1974.

I am fairly certain the rear passenger side engine mount is 1975 (it is the same blue as a 1975 2F I had in there for years). The driver's side engine mount, I'm unsure if it is a early/1974 or 1975. I did that engine swap almost 20 years ago and cannot recall. But since the slave is already mounted there, I don't think it matters.

Everything is mounted on the US driver’s side. As you can see in the second photo below, the hard line is not clamped to the body due to the clamp tab being moved to the passenger’s side by 1976. A new Aisin master, OEM hard and soft lines are still available for early '74 FJ40s. If I had to move to the pax side, I'd think I'd need a hard line (NLA), new return spring and spring plate (NLA). I'd like to not have to change sides on the slave unless I have to (hard line being probably hardest to source).

View attachment 1902296
View attachment 1902299View attachment 1902300

The reason(s) this setup isn't working right are:
1. The 75-newer slave is designed to mount closer to the release arm. Putting the new slave on the early mount means the pushrod isn't long enough. Since everything else is newer, the best fix is move the SC over to the 75-newer engine mount, using a 75-76 hardline, softline and MC. I don't know if it is do-able without pulling trans to move fork, pivot ball, boot over to the other side.

2. There is a mis-match between large-bore E-74 MC and small-bore 75-newer slave cylinder, so the amount of slave travel & pedal effort is too low.

While were looking at these pichers, the upper mounting rubber is upside-down.

 

[hobbes]

On the engine mounts, I have them with the curved parts facing the engine mount. I take it both go flat side down.

Jim makes the most sense to me because I'm pretty sure I was seeing this problem 20 years ago when I did the original 1975 2F swap. That would explain everything to me since I've swapped almost everything over the years. In the "fork" link in the first post, I was able to install the fork and pivot on the driver's side with the transmission in. So I should be able to get it out. The question is if I can get it in the passenger side.

@FJ40Jim, the OEM diagrams show the hard lines as (8/74-9/75) and (9/75-9/77) each with its associated soft line. It would appear CruiserParts lists used hard lines (1976-1980) as available. SOR has no hard lines, but they do show stainless steel lines. OEM are all NLA. So I'm hoping I can go with a 9/75-9/77 used hard line (31481-60212, I think), 76-8/77 soft hose, 75+ master, and current slave. Sound right?

So this should be fun. The best part is I won't know if I can install the fork on the pax side until I get there. The down time is the biggest bummer. I'll need to try to move the fork, then order parts.

 

[hobbes]

Anyone got a clear photo of a 76 setup? As Jim noted, I'm not afraid to install things upside down if left to my own devices...