Mopar 440 engine / transmission shake


#1

Okay and now for today?s transmission challenge, and this one is driving me up the wall. This will take a while but I will get to the point.



I have a 1973 Chrysler New Yorker ~ a demo derby rescue, the car was way too good to trash. When I bought the car the exhaust system was a ruin and had a blown exhaust manifold gasket. The transmission was a bit hit and miss and the engine needed a good tune up.



So in brief I installed a rebuilt 727 tranny and new torque convertor, hung a compete new exhaust system on the car, fixed the manifold gasket, sorted a few ignition system ills and installed a new 4 barrel carb. The car now runs very well but?



I?ve got an engine vibration, mostly noticeable at low rpm and feels like a dead cylinder though that is not the case. I?ve replaced the whole ignition system end to end. All cylinder compressions are 140psi, all cylinders are firing and the exhaust note is regular with no dead beats audible. Engine is a standard 440 with cast crank.



The only thing I can think of is that the torque converter is the wrong one for this engine, the tc that came out of the car was externally balanced with a single balance weight fitted at the 9 o?clock position ? this when viewing the tc from the drive plate side with the drain plug at 12 o?clock.



I need to confirm the position of the balance weights on the new tc but I know they (2 of them) are not at 9 o?clock. I managed to get hold of some 1975 tc data sheets and they list tc #3515282 for the cast crank 440 in 1973, the tc that came out of the car isn?t listed anywhere.



I am not looking forward to pulling that tranny out again, but if I must. Are there any tranny experts out there who can confirm the correct tc for this year 440 please ?


#2

I am not a “tranny expert”, but I love the old mopars. My first car was a '69 coronet 440 with a 383 mag. What a great car. I would not expect tc weights to be in the exact same position from one unit to the next, although I cannot discount your theory. I did have a strange vibration along with a light ticking noise that turned out to be a cracked flex plate. The crack was VERY tiny. Requiring magna-fluxing to identify.
Have you considered the harmonic balancer or something on the front of the engine?


#3

Thx Tman, I didn’t expect the tc weights to be in the same position either, but at the time I didn’t have any tc docs which do show specific positions for balance weights. If I’d had those docs when I installed the tranny I might have paid a little more attention, though I did know that the cast crank 440 was externally balanced. I have 2 spare flex plates but the original looked fine.

I also suspected the harmonic balancer - anything but dragging that tranny out again, but it looks intact. I’m trying to resist panic and desperation, if I can confirm the tc is right or wrong I’ll know exactly how bleak next weekend will look.


#4

Have you checked the motor-mounts and transmission mounts? That 440 kicks out a lot of torque at the low end-- it can be very hard on a set of mounts!

I’m guessing in the process of pulling everything out and putting it back in, you probably would have checked this, but you didn’t mention it.


#5

I was unaware of the external crank balancing. I made a call to a buddy of mine that has a lot more experience on 440’s than I do. He says that the early cranks did not use a weighted tc. He said that there should be only 2 options. Weighted or not weighted. Perhaps your engine is earler than '73 and doesn’t require weighting. Good Luck


#6

Thx again Tman, forged crank engines are internally balanced and don’t use a balanced tc and yes you would think that the 440 would have only 1 weighted tc, the tech docs published by Mopar in 75 indicate 4 possible tcs for that engine depending on the year. More irritating was the ommission of the tc that I removed from the car, I don’t remember this vibration prior to the change out but the engine was running a little rough.

I’ll stay with it, thanks.


#7

Good call, and the motor mounts looked suspect, I replaced both of them ~ a truly dreadful job ~ along with a new tranny mount. Though the vibration was a little dimished, it was still there. Another thing I plan to look into is the new exhaust, this might be excerting engine bending stresses on the block, I put a jack under it to no effect but I’ll probably dismount the pipeline and prop it on wooden blocks just for fun.

Other than that, my current strategy is to establish the position of the weights on the new tc and negate them with weights glued diagonally opposite on the faceplate of the tc. Plus I could add another weight at the 9 o’clock position to match the original tc removed from the car.

I’m hoping this will give me some direction unless I can establish the correctness of the new tc.


#8

It would make more sense to put the balance weights on the flywheel/flex plate. Transmissions come out and go in all the time with no instructions on where to put balance weights. The flex plate should go on the same way it came off. Chevy had weights on the flex plate for the 400 engine and had no weights for the 350 engine. You can see the impression (shaded area) on the flex plate where it matched up to the crankshaft. The other way to do things would to have the gear teeth for the starter welded to the torque converter, in which case the layout is the way you said it was. Then I wouldn’t know. I do know that the engine will shake things up a bit if a weight is missing. Had a chevy 350 where a 400 was supposed to be. It shook in neutral but wasn’t felt in drive.


#9

FOUR !?!?, man, that sucks. I’ll check with some car club guys I know. I’ll get back to you in a couple of days. Those guys seem to know everything. Sure will be fun cruisin around with 7 or 8 of your best friends in that land yacht, when you get it lined out.


#10

I wish, at least the flex plate to tc bolt holes have offsets so you can only hook up in 1 position. I marked everything up with a Sharpie anyway being distrustful. Starter ring is welded to the tc, all 4 slightly different year options…what the ???

Small wonder Chrysler went down the pan if you need a physics degree to install a tranny.


#11

This is what my supplier shows for a 73-76 440 with cast crank.

transman


#12

Thanks Transman, I hoped you’d be around.

Well that clarifies things…sort of.

Neither the original or the replacement TC have those weights shown on the upper picture (#2.jpg) on the front !!!

The original does have a single balance weight on the outer case behind the ring gear shown in the lower picture (#1.jpg), though not in that position.

The 1975 Mopar torque convertor tech sheet I have lists 4 440 engine A-731 tc options for years 72 ? 74 plus other A-862 options?ugh !

#2801359 is for forged crank HP engines, so I?ll forget that, though it is listed for the 73 440 C body ? my car. Confused enough so far ?

#3410839, #3515282 & #3515499 are all the same convertor with different weight sizes and positions, they don?t differ greatly to be honest but possibly enough to give a little vibration.

The one shown in your pictures looks to be the mean average of the weight positioning, that is A-731 unit #3515282 and is listed for the 440 4V cast crank engine. The new unit I have is original Mopar, fresh in the box complete with ring gear. The old unit also looks to be Mopar (it?s blue).

I think the weights I see on the original and new tc are the tc balance weights only and not the engine balance weights shown in your picture.

So the bottom line is either this is a cop engine and the NYPD use to cruise around in sky blue New Yorkers back in 73 or both torque convertors are wrong. Common sense tends to discount the former option.

Since I have the weight dimension and positions I?ll make up a couple of weights and gorilla glue them to the front of the tc next weekend, if that does the trick I?ll weld them in place with a heat sink.

Thanks for your help, this really clears some of the fog. If you want a copy of the Mopar specs I have let me know and I?ll post a copy. These are technical drawings with all dimensions and a confusing array of options I got through a torturous route to someone who used to work for Mopar and had a copy in his basement.

In the meantime, I?m going to drop the IRS rear axle unit out of my Jaguar, this is relatively much more fun than the Chrysler at the moment.