McLeod twin disk knocking

[DRJDVM's '69]

I'm starting to lean towards it actually being the T56 and not the clutch.....

Got under the car again and tried to listen real close....even used my stethoscope...... it still hard to know for sure but I can hear it just as well on the trans as the bell.. maybe even a little louder.... the case is thicker and listening through oil, so its hard to really be sure

Plus I have noticed that it seem louder as the car warms up.... like if the oil was warming up ...... plus makes more sense if the noise is gone when the clutch is IN........ and you can rev the motor up high and no noise at all....

[Blown353]

For clutches with non-sprung hubs like the Mcleod, sitting in neutral with the clutch engaged (foot off the pedal) can often generate gear rattle in the transmission that is then carried up through the shift handle. The non-sprung clutch hubs don’t absorb any vibration from the engine firing events and the gears “knock” back and forth against each other. A bigger cam with a lopey idle exacerbates this issue. Gear rattle is a big reason why OEMs like to use dual mass flywheels, they smooth out the torque delivery to the transmission especially at lower RPM and cut down on NVH. (Of course, a dual mass flywheel presents another can of worms if/when the moving elements inside it decide not to move anymore or the springs break.)

The transmission gear rattle with a solid hub clutch may also be audible while driving at lower RPMs as the solid hubs won’t dampen the pulsations from the engine. Accelerating in overdrive gears at lower RPM tend to be the worst for this as the torque requirements are higher and engine RPM is lower.

If it’s gear rattle, you can always try isolating the shift handle like the OEMs do, often with a rubber isolator in the handle itself. That will help cut down on the amount of gear rattle carried into the car. A buddy has a 2006 GTO with a Monster dual disc clutch with solid hubs. The gear rattle was barely detectable with the stock shifter and handle which had some rubber isolators, but when we put in a Ripshift shifter, a bronze shift bushing, and a solid mounted steel hurst shift handle the gear rattle at idle and at low RPM in 5th and 6th became much more noticeable.

With a dual disc clutch like the Mcleod, any noise with the clutch depressed while sitting stopped is usually the floater plate in the clutch moving around a bit.

[DRJDVM's '69]

Interesting.. thx for the info..

You cant really hear or feel the noise from inside the car but outside with it idling.... and kneel down or get under the car and you can definitely hear the "rattle".....if you stick your head in the engine bay back by the bell you can hear it... but otherwise its not real obvious unless you know its there... which I do, so I'm hyper aware of it....

Since the noise isnt really transmitting into the car via the shifter, I dont think an isolator will help in this case

Think I'm going to just run it..... I at least feel more comfortable knowing that I'm not crazy and its nothing that its truly "wrong" where something bad is going to happen if I dont ID and fix it

[Blown353]

If your bellhousing alignment was good, and nothing in the clutch or throwout bearing are rubbing inside the bellhousing, I'm pretty sure you're dealing with gear rattle, especially since you said you really only hear it stopped in neutral with the clutch out.

What fluid are you running?

Thinner fluids like ATF make the rattle a little worse since it's such low viscosity.

The rattle gets quieter with syncromesh since it's a little thicker and dampens the gear contact better (Tremec brands their own blend of syncromesh fluid now, HP-MTF)

It's even quieter still with Redline Superlight shockproof.

Years ago Dodge had a TSB for gear rattle in the T56 in the Vipers... the "fix" was thicker fluid.

Worst neutral clutch out gear rattle I've ever heard was in a brand new C6 Z06... sounded like a paint can half full of rice being aggressively shaken behind you. LOL!

[DRJDVM's '69]

I'm just running the Dexron III that the big orange sticker on the site of the trans says to use.....
As I noted before, the noise seems to get more noticeable once the car has warmed up, so I was wondering if it had to do with the oil getting warmed up and thinner....

No harm in swapping out the fluid and see what it does....

This the one you are talking about?
https://www.summitracing.com/parts/red-58404

[DRJDVM's '69]

Or maybe this?
https://www.summitracing.com/parts/rpo-01512

[Blown353]

Ned,

The fluid Tremec had made to their specs is this:

https://www.summitracing.com/parts/awr-tukt-16993

Not sure who's making it for them. Pennsoil, Valvoline, AMSoil, and Royal Purple all seem to make variants of syncromesh fluid.

While I haven't tried it yet, it's probably hard to go wrong with the fluid that the manufacturer says will have the best results.

As far as the Redline shockproof, I've tried the lightweight and superlight shockproof in the T56/TR6060. The lightweight shockproof is thicker and will better dampen gear rattle, but IMO it's too thick and makes the already notchy T56/TR6060 shifting (especially into 2nd gear when cold) even notchier. The superlight shockproof is better suited IMO.

[AMSOILGUY]

Holy smokes 91 dollars for 4 quarts of tranny fluid is crazy. You can get the AMSOIL product for 10 dollars less a quart and you know who makes it.
Ned they have free shipping on orders of 49 dollars. Use Promo code SHOP1220
Heres a link to the product: Synchromesh

[DRJDVM's '69]

Even better news.... the trans rear seal was leaking...come to find out I have one of the Tremec tail shafts that they forgot to machine the small drain holes into... so I have to remove the tail shaft housing and swap it out with a new one that Tremec is replacing under warranty...... but I have to pull the trans to remove it..... joy....

[Spiffav8]

Originally Posted by DRJDVM's '69

Even better news.... the trans rear seal was leaking...come to find out I have one of the Tremec tail shafts that they forgot to machine the small drain holes into... so I have to remove the tail shaft housing and swap it out with a new one that Tremec is replacing under warranty...... but I have to pull the trans to remove it..... joy....

Welcome to the club brother!