Transmission - unable to downshift

[Esteban]

I think John is correct on where you place the shim. It was for me the first time that I read about that shim in the Service Manual.

My experience with the clutch has been slightly different, and more on the easy side, even after running the original pressure plate for close to 300k miles (this Patrol was always a daily driver ). I changed it 16k miles ago, because I had a spare one. I have changed the clutch disk a number of times, and basically at every engine rebuilt, and dismantled the clutch cover a number of times, used emery cloth to polish it, and then cleaned and lubed the pivot points (very clear all the pivot points in the diagram above). Only time I had troubles is when I fitted a poorly done relined disk and the clutch didn't want to disengage. Had to install a new one and new synchros as well.

Don't get too concerned about the clutch. First check the conditions of the flywheel surface, and also of the pressure plate, and then you can make a decision on whether you need it rebuilt or not. If you are going to dismantle it, make good markings about the position or the pressure plate and the cover, so they go back in the same place for balancing purposes. Measure the thickness of the pressure plate (I've never done it! so I have no clue on where to measure it) and compare with the one from the manual, 15mm (0.595")

As John mentioned, calibration is a must. The best time to do it is when the flywheel is out

.. Also, since they don't seem to publish the original thickness of the PP friction disk, we're flying blind. I can say that I'm suspicious of mine since I don't have any clutch adjustment left despite my clutch disk being at the full, brand-new thickness. John

The newer Service Manual has this data:

Thickness of disc assembly mm (in)

Free ................... 10.1 to 10.6 (0.398 to 0.417)
Installed .............. 9.1 to 9.7 (0.358 to 0.382)

[ckhorne]

Ugh... Well, I guess the silver lining is that my transmission is likely ok (aside for the pitted gears), and it's only the clutch that's out of whack. But this doesn't sound too promising.

As John mentioned, calibration is a must. The best time to do it is when the flywheel is out

Well, that would be now. My clutch itself looks fine - I wasn't planning on replacing it, and I wasn't planning on having my pressure plate rebuilt.

Is this calibration something I can do myself (with calibers and careful measurement), or is this something only a shop can do? If a shop, what kind am I looking for?

[Esteban]

Is this calibration something I can do myself (with calibers and careful measurement), or is this something only a shop can do? If a shop, what kind am I looking for?

Absolutely. You've already worked on the engine so this is simpler. The whole idea is that when the pressure plate and disk are installed on the flywheel, the 3 adjuster bolts on the release levers end up at the same distance from the flywheel. You'll have to figure out a way to measure it according to the Service Manual. The special tool that the manual shows is just a measuring jig to speed up the job at the shop. Nothing extraordinary there.

Good luck.

[jwgreen]

The way I did this adjustment was with the flywheel removed I,

placed the flywheel on my work bench, then bolted the clutch assembly to the flywheel

Then using a long steel ruler laid across the top of the assembly I measured the distance from the flywheel surface to the top of the clutch assembly with a second ruler lets say that's 3"

Then taking the correct adjustment from the manual, let's say it says 2" from the flywheel surface, I use the second ruler to measure down to the adjusters, so measure 1" down from the bottom of the ruler and the adjusters should be 2" from the surface. I posted a comment on Faux40's build about this as well.

The numbers above are just a idea as I don't have a manual in front of me but if you look up Faux's thread you will see this discussed thoroughly.

Hope this helps

[ckhorne]

Great- thanks for the tips. I think that all makes sense. I'll give it a try tomorrow or Monday - doesn't sound too hard now that you've described it.

Can the throw be tested without being all hooked back up within the vehicle? IE- can I check the range of motion without reconnecting the clutch pedal? (I haven't read the service manual yet...)

[Pinto2424]

ckhorn,

I know this is an older thread, but I am new to the forum and was curious if you ever solved the downshift problem. My 79 does the same thing. Upshift no drama. 3rd to 2nd, I need to be going about 15 mph or less...2nd to 1st, a complete stop is required. Be safe!

[ckhorne]

Unfortunately, no. I did pick up some new synchronizer rings from another club member, but I havent had a chance to install them to see if that will hope. Other than that, I think its just adapting our driving styles...

[Pinto2424]

Appreciate the rely, I have adapted, usually having to come to almost a complete stop, much to the annoyance and great displeasure of the motoring public, to down shift, but there it is. Thanks again, be safe!

[Esteban]

You'll have learn and master the "double clutch" technique.

[ckhorne]

You'll have learn and master the "double clutch" technique.

I've tried double clutching, triple clutching, smooth talking to my clutch, and every other technique that should help, but I always have the same problem - it won't downshift without grinding gears, and to go back into 1st requires a full stop. I'll report back when I get my new synchros installed (but it'll be a while - my Patrol is in pieces right now while I attempt to paint it).