Transmission vibration

I recenatly had the auto trans replaced in my '94 full size ford van. I had a trans shop replace the 3 speed auto with an overdrive automatic. I now have a vibration between 50 and 60 mph. If I let it shift from drive to OD between 50 and 60 it instantly starts vibrating. So it seems that the problem would not be the drive shaft or output yoke. Is the torque converter and the flex plate and ring gear supposed to be balanced to each other? When they put in the OD trans they said they put in a new torque converter. I have had it back to the shop and they say there is nothing that they can do about the problem. One employee just says there is no vibration. At the bottom of the converter housing there is an inspection plate. It looks like you can unbolt the converter, rotate the engine until the bolt holes line up again and bolt it in place. Would the converter drop down if unbolted? Would rotating the converter and bolting it in a new place possibly affect the balance? I am thinking that this may increase or reduce the vibration. I don’t know waht to do and the trans shop doesn’t either. Sign me “all shook up in Phoenix”

Does it feel like you are driving over rumble strips at the side of the interstate?

Yes, slightly similar to that. No vibration if I keep it in high at 50 to 60 and don’t let it go into overdrive.

If this vibration were a balance problem at the flex plate and torque converter, you would have the vibration whenever the engine was turning at high RPM – even without driving. I am not sure if you have a lockup torque converter in this transmission. If you do it might be a problem with the TCC or its control circuit.

Rumble-strip is often used to describe TC lockup shudder that can be caused by old fluid or bad lockup clutch material. Are you sure it is an 3 to 4 shift or is it the TC lockup you are feeling? I suspect, however, management problems. I don?t know what trans was used in ?94. That was within a couple of years of when Ford was shifting from the aod to aode (e=electronic) transmission for some light truck and full-size sedan applications. I don?t know anything about 3-speed. I thought that was over before then. If the shop did not know what it was doing, there could be lots of problems caused by the wrong signals being sent to the transmission.

I suggest you find a Ford truck board if you get no joy here. There are often lots of people that know what transplants are practical and how to do them. Factory-trained techs often don?t have this knowledge because they just don?t try to do this kind of stuff. I would hope that your shop tried something that was in the realm of possible and advisable, but I have fear.

The converter will not drop down if you remove the inspection cover and remove the torque coverter bolts. They should be match marked but who knows. Just mark it so you can put it back the same way; just in case.

Just curious. Which engine do you have? There are a number of engine options and they all use different harmonic balancers/flexplates/converters.
The 5.0 even has 2 different balancers (28 and 50 oz.) available depending on year and application.

Normally, that rumble strip vibration is a torque converter shudder and fresh fluid (Mercon V) will cure it or in some cases a new converter is needed. Since they say they put in a new converter what is the story behind the transmission?
Is this trans an early non-electronic AOD? What year? New, rebuilt, or used transmission?
I’m assuming this swap was done to improve fuel economy.

The details behind the balancers/flexplates/converters are pretty fuzzy to me so you might consider fishing around on the net this weekend for more detailed info.
I ran into an early Ford AOD trans swap vibration problem many years ago but I just don’t remember the details behind it. Seems like a late 70s OD transmission was not working well with a late 80s V-8 and had a subtle, but chronic, vibration in it.

The engine is the 300 inch six. The van only has 54k miles on it. The replacement trans and TC are a rebuilt non electronic aod. I wish I had a tach so I could search for the vibration in other gears (or nuetral) than OD. The vibration doesn’t seem to be noticible except in OD between 50 and 60 mph.

Have someone do a check of the line pressure when this vibration occurs. The AOD uses a throttle valve pressure to adjust line pressure. Make sure that the linkage to the throttle is adjust correctly. It is possible that the retrofit did not produce the correct adjustment of the throttle valve setting. It sounds like you might be getting slippage in the overdrive band that goes away as the engine speed or throttle openning increases.

Get back to us when you have more news on this problem.

I don’t know about slippage. between 50 and 60 the vibration is there whether accelerating, steady speed, or coasting-slowing down with the gas off. I guess I will take it back to the trans shop and tell them to keep it until it is fixed. First I have to come up with some alternative transportation.