[kirkm76]

Hello,
I have a 68 std with 302 and a c4. Just wondering if anyone knows what that big metal thing is that hangs off of the tailhousing on the c4. Is this some sort of ballancer or something. I have been trying to pinpoint a vibration and found this to be very loose. Tightening lessened the vibration. What happens if I take this off? Also, When I put in my engine, the ballance factor changed from 28 oz to 50 oz. I used a the 50 oz flexplate, but would anything in the trans itself need changed?

 

[Royce Peterson]

If you changed the balance factor from 28 oz to 50 oz you would also need to use the late model 4 bolt harmonic balancer unless you had the entire rotating assembly spin balanced (pistons, rods, crankshaft, flexplate, harmonic balancer).

The big weight is a counterbalance which is supposed to dampen some driveshaft vibration. It was used on some 1968 Cougars. Others seem to never have had it and don't have unusual vibration. I don't think it matters much.

 

[kirkm76]

The engine was spin ballanced when it was assembled.

 

[TheRktmn]

Does the vibration occur when going down the road, parked or both? Does it increase with RPM/Speed?
If only when moving I would look at the driveshaft & u-joints.
If it happens all the time, when stationary or moving, I would lean toward loose flexplate or torque converter, possibly bad front pump in tranny.

 

[Royce Peterson]

Did you ever try a compression check? A mis adjusted valve on a new engine will cause nasty vibrations.

 

[greggieatthebat]

I don't know about the vibration, but as far as I could tell that big metal piece is just there to protect the transmition from debris under the car; I think it also blocks the u-joint? Dad and I wondered about it too when we removed my tranny...

 

[kirkm76]

vibration

I did check compression and it was good. I am leaning towards the front pump/torque converter. This is the second time I've heard that mentioned. But the trans seems to shift and operate normally, except the vibration. The engine ran fine in the donor car and we didn't change the flexplate. Does changing the front pump necesitate a rebuild? I am converting to an AOD soon (just waiting for the trans), but I may end up having to hold off on that due to the fact that it's my only car now and may not be able to take it down for that long. So how big of an ordeal is it to change the front pump and convertor in a c4 and is there a definite way to tell that they are indeed bad. I am new to automatics, but not scared of em'

 

[CougarAOD]

Personally, I have never heard of a transmission's pump causing a vibration that you'd feel in the car. Torque convertor---that is the most likely part of the transmission to cause a vibration.
You may want to check these before you purchase any new parts. When you installed the motor, did you make sure the drain plug ont he convertor went through and opening in the flex plate? I have seen that sometimes the counterweight covers up one of the holes and Murphy's Law would haev it that is the hole drain plug got lined up with. When you have your inspection cover off, start your engine and make sure the flex plate isn't wobbling as it rotates. A wobble can be caused when during the installation the convertor pilot will get hung up in the crankshaft and not pull forward into the flexplate. If one convertor nut is tightened down it will acutally bend the flex plate to the convertor and since it is tighten down, the nut will hold it there. Even when the other convertor nuts are tightened, the flex plate will still nut run true. What I normally do when installing the converto nuts is put one nut on about 2 threads, then insert a big flat head screw driver between the nut and the flex plate and try to pry on the nut, this should bring the convertor forward evenly into the pilot. Sometimes it takes a bit of jiggling with the screwdriver to seat the convertor to the flexplate.


hope this helps ya,
]

 

[kirkm76]

Cool, I figure that this is something I boned up since this was my first time installing an engine, so that seems likely. If that is the case can it be corrected by loosening and re-tightening the flexplate or will I need to purchase a new flexplate. The trans was fine hooked to the old engine and the new engine was fine in the donor car, so I'm 99% sure it's something like what you described related to my installation.

 

[TheRktmn]

Aah, I just realized that this is a new post of an old problem.
The reason I mentioned front pump was because you may not have seated the converter in the pump correctly. This would also cause the flexplate to "bend" and vibrate.
In any event, if both engine and tranny were working good before you swapped them into this car I would check that the converter is bolted to the flexplate correctly per CougarAOD's post. If that looks good and all the nuts are tight then I pull them and check my installation: Flexplate bolts, converter seated in pump, etc.
I wouldn't tear into the C4 since it was fine and there are other things to check first.
BTW - when installing a converter I put a thin coat of grease on the "pilot" of the converter and the receiver on the crank. Then I fit the converter to the engine to make sure that it does slide in easily. Just a little insurance that the converter does slide in and seat correctly.

 

[kirkm76]

Well, I looked at the flexplate through the inspection cover with it running and it looked o.k. I am going to pull it apart and re-install the whole works properly this weekend. I have driven all over with this and it doesn't seem to adversly effect anything other than my nerves. A transmission shop guy suggested re-positioning the torque converter on the flexplate (rotating 90 degrees at a time). You think that'll acomplish anything. Anyway, looks like I may accelerate the AOD/3.55 rear swap if I can't iron this out.

 

[CougarAOD]

Bob (The Rtkmn) is right by saying to put some grease on the convertor pilot. Seems strange that I left that out, since working at a trans shop I do it to every trans I install. I personally like to use antiseize lube--the silver stuff. But any grease will work just fine.
It is gonna be a pain to turn this convertor 90 degrees, you'll have to remove the bellhousing bolts and pull the trans back away from the motor and inch or so to be able to spin the convertor.
Did you verify that the flex plate is wobbling ?

Hey Bob, are you going to the nats? I'd really like to see another 460 Cougar show up. I'll definitely be there with my 70 with the 460. Hopefully I'll have built a better 460, the one I have now is a turtle, only making about 300 horse. I saw your pics of your motor and car, looks really nice. Those FPA headers, did you have any clearance problems and what mounts did you use? Also, are you running a C-6?

 

[TheRktmn]

I sure hope to be there. As you can see I have a lot to do. The plan is to have it together by late April so I can get the bugs out by June. I really do want to meet some cougar folks in person and seeing another 460 would be great!
The FPA headers work great with the Crites mounts but will not work with the FE mounts. The rubber mount hits the headers. DOH!

 

[TheRktmn]

Hey Kirkm76:

Did you find the problem? What was it?