Second opinion on torque converter vibration please.

[ajlelectronics]

I have a Scimitar in that I bought because the PO had nothing but trouble with it. I bought it off him expecting to turn it around quite quickly after doing one or two little jobs. Not so, it has fought me every step of the way and it is still cluttering up my yard.

Main issue is that of a resonance vibration. You can feel it at idle, but raising the revs really provokes it and the whole car shakes. I have had the engine out twice and stripped / rebuilt it with no fault found, although I did renew the piston rings and core plugs last time. Bearings are all in decent nick and there is no excessive float anywhere. It isn't misfiring, All electrics have been replaced and tested, the carburettor has been substituted with no change to the symptoms.

The car is fitted with a C3 automatic box. It occurs to me that the vibration is just like an unbalanced mass attached to the flywheel. Now I can't see any way that the torque converter could cause it, unless physically damaged. One useful test would have been to uncouple the torque converter from the flex plate, but on the C3, the bellhousing is too small to allow them to fully uncouple. The flex plate has recesses in it for the TC studs, it's that tight in there.

Any opinions before I haul it out for a third time?

 

[mr haynes]

Given what you've tried already i'll assume engine and box mounts are ok and not hitting chassis/bodywork. Been a while since i had scimitars but worth checking exhaust mounts before removing box. Running engine without it only way i can think of ruling out converter. Is it a 5 or 5a?

 

[ajlelectronics]

Given what you've tried already i'll assume engine and box mounts are ok and not hitting chassis/bodywork. Been a while since i had scimitars but worth checking exhaust mounts before removing box. Running engine without it only way i can think of ruling out converter. Is it a 5 or 5a?

All that is fine. It is a 6a with Essex and C3 auto.

 

[mr haynes]

I do remember the box mounts tendency to pantness. Shall shovel some coal flavoured coffee on the cerebral fire see if it jogs anything

 

[Bobtail4x4]

you need to get rid of the horrible slushbox, and fit a mans manual box.

 

[8ob]

99.9% sure there will be slop between the spigot on the torque converter and the hole/bush in the end of the crank, chased a similar problem around on a conversion and five thou is enough set up a vibration with the kind of weight involved. Easy enough to check, release bolts on tc and see if you can get any up/ down movement on the t/c.

Bob

Edit: above doesn't read right What I was trying to say was that unless the spigot on the torque convertor is a good fit in the crank it will be on the squiff/out of balance when you nip up the bolts holding it to the flexplate.

 

[Morrisman]

I One useful test would have been to uncouple the torque converter from the flex plate, but on the C3, the bellhousing is too small to allow them to fully uncouple. The flex plate has recesses in it for the TC studs, it's that tight in there.

Any opinions before I haul it out for a third time?

Any chance you can space the tranny casing from the motor, maybe loosen the housing bolts, lever back, slip something in, or put some washers in, under the bolts?

I have a C3 on the back of the Essex in my t bucket, but not run it in anger yet.

 

[Morrisman]

you need to get rid of the horrible slushbox, and fit a mans manual box.

That’s what I want to do with mine, ’real men shift their own gears’.......

 

[ajlelectronics]

That’s what I want to do with mine, ’real men shift their own gears’.......

Only those who enjoy stirring puddings. An auto box is far superior once we get past the C3! The A4LD onwards are superb gearboxes and are what's needed in a quality cruiser.

 

[8ob]

That’s what I want to do with mine, ’real men shift their own gears’.......

With a real mans motor you would probably be too scared to take your hands off the steering wheel.

Bob

 

[Morrisman]

With a real mans motor you would be probably be too scared to take your hands off the steering wheel.

Bob

My old ride.

 

[Morrisman]

Only those who enjoy stirring puddings. An auto box is far superior once we get past the C3! The A4LD onwards are superb gearboxes and are what's needed in a quality cruiser.

I’d definitely like an auto box in my daily driver, diesel Mondeo, but for a hot rod I’d prefer a stick for a change. The last three I built were auto.

 

[8ob]

I’d definitely like an auto box in my daily driver, diesel Mondeo, but for a hot rod I’d prefer a stick for a change. The last three I built were auto.

I too like a stick change but V8 motors needs to be cammed to suit, long before the yanks came up with a decent overdrive five speed box I made a mold and cast a bell housing to run the 265 getrag behind yank V8`s, made it dual starter positions so it would take all GM offerings including BOP.


Top left is the original beemer bellhousing, new mold top right.

 

[stuvy]

Is there vibration when it’s sitting stationary or on the move?

 

[ajlelectronics]

Is there vibration when it’s sitting stationary or on the move?

It isn't insured so it's just sitting still. My autobox engineers tell me that the only thing that can cause it is a shoddy TC rebuild, otherwise it's highly unlikely.

 

[stuvy]

Do you have a spare box to swap it over to try that?

I’d also be looking at what bob mentioned as we had an engine built for a car at work and it was built badly by an idiot(when I leave I will update this) but it too was missing a bush at the end of the crank

Was rather embarrassing as it had only just gone back together and needed to take the box out at a circuit between races

 

[ajlelectronics]

Do you have a spare box to swap it over to try that?

I’d also be looking at what bob mentioned as we had an engine built for a car at work and it was built badly by an idiot(when I leave I will update this) but it too was missing a bush at the end of the crank

Was rather embarrassing as it had only just gone back together and needed to take the box out at a circuit between races

I have a spare TC but I was trying to avoid dragging the lump out for the third time! Due to my lift design, I can't pull the gearbox on its own, has to be the power plant.

 

[stuvy]

I have a spare TC but I was trying to avoid dragging the lump out for the third time! Due to my lift design, I can't pull the gearbox on its own, has to be the power plant.

Re engineer the lift

 

[CKJDJK]

Could it be the engine? Mis matched pistons/rods or out of balance crank? Fly wheel fitted incorrectly or distorted? Faulty cam? Really need to separate the engine/box and run engine on it own as there are so many variables.

 

[mr haynes]

Re engineer the lift

...or driveway repair styley with wee ramps/axle stands and bit of old carpet for your back