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TR2/3/3A The "Counterweight" on the 4A gearbox.

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karls59tr

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I think I remember reading somewhere that the counterweight was added to the 4A gearbox back in the day because customers were complaining about the noisy, buzz rattling of the gear lever. My TR3A still has this buzz even after installing a new spring on the gear lever and adding a 3/4" rubber spacer. I have a counterweight from a 4A and was thinking of installing it on the 3A gearbox as a solution. Any thoughts?
 
Worth a try, but I don't hold out a lot of hope that it will help. Did you also replace the little plunger and spring at the bottom end of the shift lever?
 
Hard to get a tranny out of balance. It's usually the clutch and/or flywheel that are off and cause the vibration. They get surfaced and rarely rebalanced afterward.

They should be balanced together, and throw in the crank, pistons, rods, rings and nose piece to get it really smooth.
 
karls59tr said:
I think I remember reading somewhere that the counterweight was added to the 4A gearbox back in the day because customers were complaining about the noisy, buzz rattling of the gear lever. My TR3A still has this buzz even after installing a new spring on the gear lever and adding a 3/4" rubber spacer. I have a counterweight from a 4A and was thinking of installing it on the 3A gearbox as a solution. Any thoughts?
Click to expand...
I replaced those. I heard of installing a 3/4"piece of rubber hose on the gear lever but I think I installed it under the Cap when maybe I should have installed it at the Retainer spring?
TR3driver said:
Worth a try, but I don't hold out a lot of hope that it will help. Did you also replace the little plunger and spring at the bottom end of the shift lever?
Click to expand...
 
Aaah, that weight. I'd call that a damper instead of a counterweight. Balancing the engine and flywheel is still the best way to get rid of the rattling.
 
karls59tr said:
Looking at the Moss diagram ....they mean the rubber piece goes "under" the fulcrum ball. Correct?
Click to expand...
Not sure which diagram you are looking at. The factory instructions that I posted above call for the rubber to be above the ball, but in contact with it. With the length they specify, I suspect it winds up touching the inner cover as well. But I haven't tried it.

Another "fix" worth trying might be the strap from the cover bolt down to the gearbox mount. Should be easy enough to make one yourself; just be sure it doesn't try to bend the top cover.

Funny thing is, I've never had any trouble with the TR3 shift lever rattling, even though I've had some engines and driveshafts that were pretty badly out of balance. Always assumed that its short, stout construction (compared to the later cars) prevented the resonance (or moved it too high to be a problem).
 
karls59tr said:
I replaced those.
Click to expand...

It might not help if you replaced them with either a spring too short, or a plunger too short. I've seen different spring lengths and can't explain it. About using a short piece of hose; that should be installed at the base of the lever, with the small end of the inverted coiled spring slid rather tightly down around it. When you fitted the lever down home, you of course felt the pressure of the plunger compressing? On mine, I made my own plunger longer by cutting some pin stock and grinding smooth. I can easily see the other issues above also being key.
 
We had a discussion about "the lump" on the TR-Register forum recently.

We concluded:

1. it damps a PROP-SHAFT resonance
2. if you dont fit there is a risk of cracking the gbox tail-shaft housing
 
alanjohnturner said:
We had a discussion about "the lump" on the TR-Register forum recently.

We concluded:

1. it damps a PROP-SHAFT resonance
2. if you dont fit there is a risk of cracking the gbox tail-shaft housing
Click to expand...
Must be a mighty small chance; since the damper was not installed by the factory on the vast majority of cars, and is missing or ineffective on the vast majority that had it once upon a time. Of all the damaged gearbox parts I've seen, the only cracked tail housing had obvious damage from some gorilla beating on it with a BFH.

According to the TR4 SPC, the "weight and bush assembly, vibration damper" was only fitted from CT17815 to CT35719.
 
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