[PFloro]

Hello All:

The C-4 in my '66 vert has been getting progressively noiser.
Here are my observations: 1) Whine is always present while
engine is running and is proportional to engine speed. 2) Whine is present in any gear selected and heard when vehicle is moving and stopped. 3) Whine is present if I 'power brake' (converter turbine not turning). 4) Fluid is clear, full and doesn't smell burnt. 5) I used to not hear the whine until the transmission fluid warmed up, now I hear it as soon as engine
is started. 6) As a test, accessory belts were removed to eliminate PS pump noise, etc. Whine was still present.

This whine was not too noticable when car was bought (almost 2 years ago). But it's now gotten progressively louder and I'm sure that a ton of 'shinies' must be in the pan by now.

Could his whine be coming from the converter? If I feel the trans dip stick tube while the enine is idling, I can 'feel' the whine as I hear it. Or could this whine be coming from the C-4 pump? While in Manchester VT this past weekend for the Hildene car show, I listened to other C-4s.
They were not whining...

Your comments are welcomed.



This whine has been gettine

 

[Ray_Hillebrand]

Change fluid and filter. Sounds to me like the front pump is having trouble getting enough fluid, they will wine when the filter is getting clogged...

 

[camachinist]

Couple of questions...

How does the trans operate during use? Any progressive abnormalities to note?

Have you changed fluid/filter during your ownership?

Do you note any bubbles on the dipstick when removing it while the engine is running? If so, approximate volume vs total volume of fluid on stick...?

Any way to quantify rpm vs mph while on the road? This observation, along with gear ratio and tire rolling radius, can be used to determine converter slippage...

It's possible the over-running clutch sprag in the converter is going or gone......some of your answers might indicate that, once they're known...

Get back to us..

 

[PFloro]

Hello camachinist:

How does the trans operate during use? Any progressive abnormalities to note? ENGAGEMENT IN FORWARD & REVERSE
IS POSITIVE AND QUICK. STRONG ACCELERATION. 1-2 SHIFT IS STRONG & WELL TIMED. 2-3 SHIFT IS A BIT SOFT WITH A HINT OF 'ENGINE SPEEDUP' (RUNAWAY) UNDER ALL TYPES OF LOADS. 3-2 & 3-2-1 KICKDOWNS ARE FINE. OTHER THAN THE 2-3 SHIFT GETTING A BIT SOFTER AND THE WHINE LOUDER, C-4 OPERATION HAS NOT CHANGED. I TRIED TO ADJUST THE KICKDOWN BAND BUT DISCOVERED THAT I COULD ONLY TURN THE ADJUSTER IN ABOUT 1 TURN BEFORE IT SNUGGED TO 10 FT/LBS. I DIDN'T DARE BACK IT OUT 1 3/4 TURNS AS THE MANUAL INDICATES FOR FEAR THAT THE 2-3 WOULD REALLY SLIDE. I SENSE THAT THE KICKDOWN BAND IS WORN AND/OR THE HIGH CLUTCH DRUM HAS A PROBLEM. PERHAPS SOMEONE IN THE PAST 'TIGHTENED' THE KICKDOWN BAND TO 'ADJUST OUT' A
VERY SOFT 2-3 SHIFT...

Have you changed fluid/filter during your ownership? NO...
I PLANNED ON THIS BUT NOW WONDER IF A TEARDOWN IS IN MY FUTURE...

Do you note any bubbles on the dipstick when removing it while the engine is running? If so, approximate volume vs total volume of fluid on stick...? NEVER ANY BUBBLES ON DIP STICK.

Any way to quantify rpm vs mph while on the road? This observation, along with gear ratio and tire rolling radius, can be used to determine converter slippage... I WILL CONNECT A TACH AND DETERMINE ENGINE RPM AT A GIVEN SPEED (SPEEDO IS ACCURATE). IF IT'S ANY MEASURE, I JUST RETURNED FROM A 500+ TRIP AND AVERAGED 16.0 MPG AT A STEADY 65-70 MPH. (2.80 AXLE RATIO AND P205/70R14 TIRES)

It's possible the over-running clutch sprag in the converter is going or gone......some of your answers might indicate that, once they're known... I UNDERSTAND THAT THE
CONVERTER STATOR CLUTCH SHOULD HOLD DURING 'VORTEX FLOW'
(TORQUE MULTIPLICATION MODE) AND OVERRUN DURING 'ROTARY FLOW' (COUPLING MODE)...

I WILL FOLLOW UP... THANKS.

 

[camachinist]

Excellent...your road test results will likely be definitive.

I think your instincts (and mine) are pointing towards the converter as the culprit here...

I've had stator sprags fail on racing converters in the past but never on a muffled car where I could tell the audible symptoms. My only way of knowing was a modest increase in trap rpm vs recorded mph. There wasn't even any debris in the pan. The only way I found out the first time was by calling the converter mfg and sharing the symptoms. They educated me...*G*

I could be wrong but a rebuilt converter might be in your future...if there's no debris in the pan other than friction residues and the trans operates fine, you might be able to just replace the converter and seal (an inspection of the converter snout will indicate whether the support bushing is still OK), which would obviate disassembling the trans. If this is the course you take, I might suggest, when pulling the pan and changing the filter, that you install a shift kit (if to your knowledge none is currently installed); this can markedly extend the life of the existing trans, if in good operational condition.

Update us when you have further information...good luck!

 

[PFloro]

Hello Pat:

I will get a tach on & measure RPM at various speeds ASAP.

I was planning on installing a shift kit but have not seen
one for this 1965/6 C-4 (checked B&M and Transgo web sites).
My trans has the 'dual range' valve body as it will start &
stay in 2nd if I select the 'green dot' range. Do you have
a suggestion for a 'shift improver kit' for this trans? I'm a firm believer in shift kits! Also, in deciding wether or not to do a rebuild, should I be concerned about the present
soft 2-3 shift and the already 'tighter' kickdown band?? Perhaps that high clutch is leaking a bit, yet reverse engagement is quick & positive...

Many thanks,

 

[camachinist]

Regarding shift kits, please see here. I've had good success with their converters in the race car. Another option is to check with a local transmission rebuilder and see if they can supply you with a generic shift kit. One of my customers is in this business and both the D-coder and race car have these kits, which cost me around 10.00 ea (way back when *G*)...your valve body is consistent with those in the 64.5-66 model years (green dot)...

Running a later valve body in the early C4 (like from a '67) is another option, and will give you better control of shifts at high rpms, if applicable.

You'll find that, in the instructions for shift kits, they'll recommend band adjustments. As the shift kit changes the pressure and timing of the shifts, firming them up, having the band at the proper clearance is important for smooth operation. If, when dropping the pan, you don't note excessive band and clutch particles (some is OK), your band likely is OK for continued service. Inspection of the drum, once the valve body is out (to install the shift kit), will also be indicative of whether a rebuild is necessary.

If you have a leaking clutch piston seal, you might experience a soft shift, as noted, or you might experience no shift under load in an extreme instance, or the inability to engage certain forward gears, especially when fluids are cold. The reason is that the same pressure which applies the high clutch is that which releases the intermediate band servo. If sufficient pressure cannot be obtained, the servo won't release and you stay in second gear. I recently worked such a problem with R100RT which you can read here

Now would be a good time to get a trans service manual, if you don't have one already...

If you have any other questions, feel free to ask..