Additive to fix Torqeflite shudder?

[Rusty Muffler]

I was just thinking of things that would spin with the driveshaft. I'm suspecting that it does spin along with the driveshaft, with a stationary backing plate and frictions as the normal drum brakes have.

Just some thoughts,
CBODY67

You have a good point because in 3rd gear at 40mph at 1550 rpm would the drive shaft by ITSELF have enough inertia to cause the vibration? I think it's spinning 1to1? I seen everything spinning under there and I don't see any kind of wobble in the parking drum or shaft.

 

[Rusty Muffler]

I've got the pan draining and the fluid looks pretty darn clean. My FSM says 11 quarts I assume dry. Anyone know what it would be wet?

 

[CBODY67]

Drums need to be balanced just like wheels do. Wobble is different..

 

[Rusty Muffler]

Drums need to be balanced just like wheels do. Wobble is different..

Drained the pan oil and it all looked clean. I taped a Q tip to a screw driver and there is a thin layer just enough to turn my finger black of black "silt" on the bottom of the pan. I looked at it with magnification and no metal is found. Not sure it's worth pulling the pan? If I pull the trans brake drum, will a tire place be able to determine if it's out of balance and remedy it?

 

[CBODY67]

Would have to see if they can get the bare drum chucked into their electronic spin balancer.

 

[Lefty71]

, should I pull the pan anyway?

Id say no. It's hard for us to understand how severe of a vibration you are chasing. I have a 64 with a ball and trunion setup. It had a worrisome vibration at higher speeds that turned out to be too much grease in the boot, most likely all in one side from sitting on a hot day?? All went away....id be pissed if i tore the car apart for nothing.
Also, you mentioned an engine miss...i would track that down if i were you.

 

[Rusty Muffler]

Id say no. It's hard for us to understand how severe of a vibration you are chasing. I have a 64 with a ball and trunion setup. It had a worrisome vibration at higher speeds that turned out to be too much grease in the boot, most likely all in one side from sitting on a hot day?? All went away....id be pissed if i tore the car apart for nothing.
Also, you mentioned an engine miss...i would track that down if i were you.

Thanks Lefty. I'm going to replace the oil and move backwards. The engine I've been forwards and backwards on if you see my previous posts. But if it is the engine or the transmission I think done and the next owner can deal with it. Some riders won't notice it but I can feel it in the steering wheel. I've already popped it into neutral at 40mph and it goes away so it's not the tires out of balance.
If it's the trans parking drum, I thought I might tape some washers to one side of it and see if things change at 40mph.

 

[300George]

My two cents worth:
Disconnect the driveshaft from the trans. Spin up to the trouble spot to eliminate shaft, drums etc. Spending 40 years of dyno testing, a lifetime of working on cars/trucks, tracking down vibration can be a challenge. Doesn't take much to trip a vibration with all that heavy stuff spinning.

 

[fury fan]

I've already popped it into neutral at 40mph and it goes away so it's not the tires out of balance.
If it's the trans parking drum, I thought I might tape some washers to one side of it and see if things change at 40mph.

If going to neutral removes the vibration, then it's not a balance issue, it's load-related.
That absolves the parking drum, too.

I would look at U-joints first. (If you have the B&T for a front joint, that's beyond my experience)

2 things that might not be apparent:
If you remove the shaft and swivel the joints, they might seem OK but yet still have very minor 'scallops' in the race of the U-joint. Most folks swivel the U-joint thru a wide range of motion, which does not emulate how it works in usage, where it only goes thru a few degrees of motion. So it feels OK because you don't notice any gross wobble issues. Also, old grease can pack into scallops also, due to the limited range of motion. But if you disassemble, you can see wear that's not as easy to feel by hand.

#2 - this is where amateur's U-joint replacement comes in:
Sometimes people just swap the new U-joint in via pressing it in the vise with some sockets, get the clips installed, and call the job complete. (I was guilty of this years ago)
Then a professional taught me to install only 2 bearings into the yoke, and swivel it afterward and check for tightness. The pressing can distort the yoke ever so slightly, making a tighter hold on the bearing. If so, put a pin-punch on an ear of the yokes, and give a healthy tap outward/away from the joint, and swivel it again. Do this iteratively on each yoke ear (1 attempt/ear) until everything is smoothest. Consider that by doing too much on only 1 ear, you can make the distortion you are trying to remove, and you'll chase your tail. When that half of U-joint swivels freely in its yoke, doe the 2nd half, and check that afterward. (yes, you can install all 4 and if all swivels freely then you're 'golden', but if it doesn't, you have 4x ears involved, instead of 2)

If the U-joint is OK, then it could be in the axle.
Years ago my parents had an 8-1/4 axle that would sometimes make a really bad shudder. My folks thought I was exagerrating the issue, wanting the old car 'to be just like new'.
I had heard somehow (this was early internet days) that 8-1/4 axles could have bad spider gears.
Finally one day the 'ole girl was bucking so hard when I left home it was practically undrivable, so I returned for Ma and Pa to experience it.
The diff cover was popped off. One of the cross shafts for the spider gears had a scallop worn about 1/8" deep (well, maybe only about .060" deep!) but there was no denying that there was indeed a problem. I presume that most of the time the parts were floating in sync, but when that got disturbed, the gears would bobble for a bit and cause vibration. (Ironically, parts were NLA at the dealer, but because the axle was made by Spicer, I found a spider gear/cross-shaft repair kit via a heavy-truck repair dealer!

 

[fury fan]

Sidebar - torque converter lockup clutch shudder:

Modern transmissions (most of them, probably) will use PWM (pulse-width modulation) to apply variable pressure on teh TC clutch, because generating pump flow (and the resulting pressure) requires horsepower and therefore costs fuel.
As there are 2 types of friction, static and dynamic, it takes more pressure to make the clutch grab, and then less pressure to hold it.
So the OEMs have an algorithm of electrical current to that solenoid, higher pressure to grab the clutch and then less to hold it. (it varies for each and every design based on a lot of factors)
Hydraulically-controlled ATs likely just apply the higher pressure required to overcome the dynamic friction at that particular PRM/load condition.

Next -
Some OEMs will have a more complex algorithm to maintain minimum pressure, relaxing it until the ECU sees a change in RPM between the engine and the input shaft of the trans, and when a threshold difference is detected (25 rpm or so?), it will bump the current to the solenoid to get a pressure increase to reduce that slip. That change in current is monitored on the next software calculation loop, and adjusted based on RPM feedback.

Variables:
commanded electrical current vs actual current to the solenoid,
intended flow/pressure increase to the clutch vs actual,
'noise' in the speed-sensor data vs actual RPM differences
fluid viscosity due to temperature and/or when the fluid is 'worn',
reduced friction coefficient in the clutch lining material due to oxidation (wet clutches do wear, that is what makes the dark silt in a trans pan, but oxidation of the fluid and of the friction material is the death sentence for a wet clutch)

So, software engineers create the algorithms with all those variables for the ECU to monitor, thousands of times per second, and if they don't have enough of a safety-buffer on them, the clutch can slip/grab excessively. At a mild level it can lead to an oxidized/heat-darkened clutch, but if the RPM oscillations are significant enough, we humans can feel it and we call it shudder. If the algorithms try to regain control of the clutch too quickly/discretely, it can lead to 'buzz' and harmonics in the controls, which leads to problems also. It's a fine balance.

Why do they create such a complex/fragile control system?
Because reducing ATF fluid flow and pressure saves fuel, a tiny bit. But add that tiny bit to all the other minor savings in the whole transmission, the whole vehicle, across the year's production volume, across all the miles those cars will drive - and it can save a LOT of barrels of oil over time. The downside is that some OEMs will have a campaign or a recall, and some folks will have a trans failure after warranty. That cost is outweighed by the overall savings across all vehicles on the road. The guy spending $5000 for a trans repair will never see it that way, of course.

So, why not just put higher pressure on it and eliminate any possible problems, you say?
Well, the trans gearbox engineers have to deal with a thing called 'the oil budget', created by the trans hydraulic engineers.
In the pursuit of all-things-minimized, the trans is designed to require less oil flow and the pump is sized (smaller) to provide that minimum amount. There is a margin of extra oil, but not an excess. The more oil used at any given component/system, the less oil available elsewhere for clutch pressure and lube/cooling. Take a guess what takes the hit when oil flow is insufficient? It's the end of the hydraulic circuits, and generally that's the tail end of the trans. And in the A500/A518 era, that was the OD section, so 'twas one of the big reasons we were told not to tow in OD.