Transmission grinding when shifting into first 1st gear help

Won't run? Engine, cooling system, fuel pump, carb, clutch, tranny, brakes, etc. The old messages from the NPCA 'Engine & Mechanical' category are here.

Postby Esteban » Wed Apr 17, 2019 7:57 pm

curlrider11 wrote:...what might this issue only happening in first and not neutral to 2nd or 3rd be an indicator of? Still the pilot bearing?


The synchronizers on 2nd and 3rd are the reason. In some other places they call them "brakes", since they actually brake the rotating movement of the axles inside the transmission to the speed of the corresponding gear that they are going to engage. In this case they brake the input shaft to equalize the speed of the 2nd or the 3rd gear, so there's no grinding noise (provided the synchro rings are good).

1st or Reverse don't have a synchronizer so the speed of the input shaft can't be reduced. Normally when you actuate the clutch at a dead stop, the input shaft and the disk will slowly stop rotating on their own and no grinding noise is present. This is not happening to curlrider11 Patrol at the moment.

This is what Wikipedia says about Synchromesh or synchronizers:
Synchromesh transmission was introduced by Cadillac in 1928. If the dog teeth make contact with the gear, but the two parts are spinning at different speeds, the teeth will fail to engage and a loud grinding sound will be heard as they clatter together. For this reason, a modern dog clutch in an automobile has a synchronizer mechanism or synchromesh, which consists of a cone clutch and blocking ring. Before the teeth can engage, the cone clutch engages first, which brings the selector and gear to the same speed using friction. Until synchronization occurs, the teeth are prevented from making contact, because further motion of the selector is prevented by a blocker (or baulk) ring. When synchronization occurs, friction on the blocker ring is relieved and it twists slightly, bringing into alignment certain grooves or notches that allow further passage of the selector which brings the teeth together. The exact design of the synchronizer varies among manufacturers.

The synchronizer has to overcome the momentum of the entire input shaft and clutch disk when it is changing shaft rpm to match the new gear ratio. It can be abused by exposure to the momentum and power of the engine, which is what happens when attempts are made to select a gear without fully disengaging the clutch. This causes extra wear on the rings and sleeves, reducing their service life. When an experimenting driver tries to "match the revs" on a synchronized transmission and force it into gear without using the clutch, the synchronizer will make up for any discrepancy in RPM. The success in engaging the gear without clutching can deceive the driver into thinking that the RPM of the layshaft and transmission were actually exactly matched. Nevertheless, approximate rev. matching with clutching can decrease the difference in rotational speed between the layshaft and transmission gear shaft, therefore decreasing synchro wear.
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Postby RiverPatrol » Thu Apr 18, 2019 8:45 am

curlrider11 wrote:
RiverPatrol wrote:When this issue occurs have you tried moving the shifter to any other gears, just to see if it could go there? I have a similar problem on one of mine, I believe it's the pilot bushing. There was a similar problem a user worked out, it was also the pilot bushing.


River, I tested out while on stands if I could shift from neutral into 2nd or 3rd. Those two gears had no grinding and we're just fine. It only happened in shifting to first or reverse. Wonder if that helps isolate.

Also, tried to see if shimming master cylinder would help in travel of cylinder, but it was already at full extension and had no need of travel further.

what might this issue only happening in first and not neutral to 2nd or 3rd be an indicator of? Still the pilot bearing?



This is what mine does as well, 1st and reverse. I do suspect your pilot bushing.
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Postby curlrider11 » Thu Apr 18, 2019 9:47 am

Excellent, I agree. looks like it's going to be a good time for a clutch relining and tranny case refurb while i'm at it. :) glad I've been saving my allowance :dance:

messaged L60Boerne to see where the best place he sourced his was from. the ebay link wasn't working on another thread about it.

Thanks for the help diagnosing friends! Here we go :)
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Postby curlrider11 » Thu Apr 18, 2019 6:20 pm

Suddenly after bleeding my clutch master cylinder all over again it seems my problem in first from neutral has disappeared. I wasn't satisfied so I took off my transmission cover and clutch inspection window and started it up in neutral with the pedal all the way down for the clutch. There was no clutch plate movement at all and that seems to have alleviated the grinding, the input drive was not spinning it all.. Maybe I had an air bubble in my line. But I can't come up with another explanation on as to why the symptoms disappeared. Hopefully that was all it was. Only thing left is to road test it and see if it vanishes or comes back.
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Postby curlrider11 » Thu Apr 18, 2019 6:57 pm

Well, I took my patrol for a spin around my neighborhood and ended up running out of gas. :oops: :roll: . Faulty gas float or something wrong with my gas gauge. Add it to the list. Waiting for my fuel level part from Colombia... In the meantime... no grinding in first from a stop. But having the transmission cover off I do notice interesting bearing noises from inside the transmission. Maybe I'll upload a video clip when I get some gas in the tank :-)
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Postby RiverPatrol » Fri Apr 19, 2019 9:26 am

Well that would be great, a simple solution is always the best one. Running out of gas is minor, you haven't truly driven a Patrol until you do it at least once. :D
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Postby curlrider11 » Fri Apr 19, 2019 5:46 pm

Haha then I'm almost a pro ....
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