BJ40 vs BJ42 clutch problem?

[rossg]

Not sure if I have a problem - but here is the situation.

I have a 1979 BJ40 which started out with the original B motor and 4 speed.

I upgraded the engine to a 3B (out of an 83 BJ42) , used the 3B bell housing, 3B flywheel and clutch from the BJ42 and bolted up a 5 speed from a BJ74.

However I kept the original clutch fork, release hub and slave cylinder from the BJ40.

I didnt notice any major issues when I installed this - and that was 10,000km ago...

However - now under closer inspection - It appears that my slave cylinder rod is too short with the two parts of the rod engaging by less than 3 - 4 mm. Something seems amiss...

Got me wondering if I have assumed parts are interchangable..

Toyota part numbers I believe are:


Fork: (BJ42) 31204-60050, (BJ40) 21204-36020
Hub: (BJ42) 31231-60060, (BJ40) 31231-36012
Bearing: (BJ42) 90363-45002, (BJ40) 90363-45079
Slave: (BJ42) 31470-60110, (BJ40) 31470-60050
Rod part #1 (BJ42) 31473-60090, (BJ40) 31473-30020
Rod part #2 (BJ42) 31474-30020, (BJ40) 31474-30020

Therefore either toyota relabled part numbers or most of these parts that I assumed would be interchangeable are not..

I also have the mystery of why I burned my clutch severly after only 5000km when I was assisting a winch recovery on a steep hill - Didnt seem like the vehicle was that stuck.. And I am barely pushing 45odd rwkw

So - back to the question - do I have a problem?

 

[lostmarbles]

Not sure if I have a problem - but here is the situation.
I have a 1979 BJ40 which started out with the original B motor and 4 speed.
I upgraded the engine to a 3B (out of an 83 BJ42) , used the 3B bell housing, 3B flywheel and clutch from the BJ42 and bolted up a 5 speed from a BJ74.
However I kept the original clutch fork, release hub and slave cylinder from the BJ40.
I didnt notice any major issues when I installed this - and that was 10,000km ago...
However - now under closer inspection - It appears that my slave cylinder rod is too short with the two parts of the rod engaging by less than 3 - 4 mm. Something seems amiss...
Got me wondering if I have assumed parts are interchangable..
Toyota part numbers I believe are:
Fork: (BJ42) 31204-60050, (BJ40) 21204-36020
Hub: (BJ42) 31231-60060, (BJ40) 31231-36012
Bearing: (BJ42) 90363-45002, (BJ40) 90363-45079
Slave: (BJ42) 31470-60110, (BJ40) 31470-60050
Rod part #1 (BJ42) 31473-60090, (BJ40) 31473-30020
Rod part #2 (BJ42) 31474-30020, (BJ40) 31474-30020
Therefore either toyota relabled part numbers or most of these parts that I assumed would be interchangeable are not..
I also have the mystery of why I burned my clutch severly after only 5000km when I was assisting a winch recovery on a steep hill - Didnt seem like the vehicle was that stuck.. And I am barely pushing 45odd rwkw
So - back to the question - do I have a problem?

Hi there Ross

Well .... Yes. You DO have a problem. (Your clutch is wearing out too fast and your clutch set-up specifications are up the poo.)

I just checked through your findings and the only thing I dispute is that I believe the clutch release forks are the same. (From what I see, you don't appear to give the correct number for the BJ40 for the release fork. I read it as 31204-60050 which is the same as the BJ42.)

And as a side note, the slave cylinders were the same (between that BJ40 and the BJ42 model) until October 1981 but you're correct that they're different for a BJ42 from then onwards.

The bellhousings are different too and if I look at an aftermarket clutch-kit supplier like "Exedy", it tells me replacement clutch kits are different between the BJ40 and the BJ42 model (and they give the same kit for all BJ42 models as shown below):



Anyway ... I think you're paying the price for "skimping on the installation work". An essential part of that work should have been checking pedal-travel, pedal height, and free-plays. (When you did that work was the appropriate time to discover any mismatch in the components you used.)

But what's done is done.

I think it is quite likely that one or more parts you have there are incompatible ... But I think it's really down to you to see if you can get the clutch specifications (travel, height, freeplay) correct with what you've got there. Or if you can't, you need to figure out for yourself what you've got to change.

If you can get away with simply a longer pushrod on your slave cylinder ... then that's an easy fix. (The existing one can be extended easily enough.)

 

[The Dude]

I did the same thing. Just extend the the push rod in the slave cylinder. (or make a new one so that it is of proper length) All other parts looked identical on the bench to me and I am willing to bet the 3B clutch has more pressure to account for the stronger engine and hence a different part number??

 

[rossg]

I know the flywheels are different and therefore the clutches are different between the B and 3B. I think there is 5mm difference in diameter of the clutch...with 3B being bigger

Considering I do I have a BJ42 clutch, flywheel, bell housing - and I am hearing that the clutch forks are the same - my issue must be slave cylinder/rod + setup..

And I assume if there was freeplay between slave rod and fork - the clutch is fully engaging when not pushing on the pedal - so pedal height and the other adjustments wouldnt effect premature wear of this clutch?

 

[Michael Hanson]

I alway replace most of those parts when doing a clutch, including rear seal and throw out bearing, clips etc. Did you turn the flywheel? Aisian Clutch? When your in there this time do it all. 2 cents MIke

 

[rossg]

flywheel was machined, clutch was a new heavy duty exceedy, new thrust bearing etc.. Fork was 6 months old along with clips etc..

 

[lostmarbles]

Considering I do I have a BJ42 clutch, flywheel, bell housing - and I am hearing that the clutch forks are the same - my issue must be slave cylinder/rod + setup..

In my opinion it may not be quite as simple because you said you used the BJ40 release hub and the BJ40 release bearing. And both of these appear to be different from the BJ42 versions that you should have in there. (So I think they could affect the setup.)

..And I assume if there was freeplay between slave rod and fork - the clutch is fully engaging when not pushing on the pedal - so pedal height and the other adjustments wouldnt effect premature wear of this clutch?

Well having freeplay between the slave rod and fork SHOULD mean the fork (and the release bearing it holds) applies no pressure to pressure plate's release fingers (and therefore won't promote disengagement/slipping).... But that is only when all components (ie fork, hub, bearing, bellhousing etc) match each other. - You have some "foreign" components in there. (Release-bearing-hub and the release bearing itself.)

I think you need to check (when you have that play there between the release-rod and the indentation in the fork), that your fork can actually be moved towards the "finger-contact/disengagement-point" by hand.

If your fork feels "solid" (and can't be moved by hand) it would suggest to me that simply bolting your motor-bellousing-gearbox together has already taken up all release fork/bearing freeplay ..... if you understand what I mean. ( I think such a thing is possible if components are mismatched so I just think it needs to be checked out. And checking it is easy enough to do.)

It would also be interesting to see how the release-bearing approaches the fingers (and exactly where it sits on them) if the hub & bearing are BJ40-specific and the flywheel & pressure plate etc are BJ42-specific. But checking that would be awkward and if you have no "unusual sounds" I think in your shoes I'd probably assume it's OK.)



Note: I tend to be a pessimist and assume things will go wrong (rather than assuming I will "luck-out") whenever I do unorthodox things. So I like to double-check everything as I go.

 

[rossg]

Also being advised by Terrain Tamer parts supplier that clutch master and clutch slave are identical between BJ40 to BJ42. Slave aftermarket part JB4069 fits both. Bore sizes are the same: 7/8 slave and 3/4 master..

 

[mldave]

On a similar thread,does using an extended slave cylinder rod damage any part of the clutch or shorten it's life span?