Hey guys I have a small problem not sure if its a problem just yet, ok I was driving my 1980 Dodge diplomat s6 Auto 4 trannie, 1 bbl holley 1945, anyway I was doing about 60 65 with it floored and a real weird vibration started felt like it was comming from transmission but can't be sure, let off gas and it went away, any ideas? I have no idea when the fluid was changed but it is full...

This could be the lock-up torque converter starting to let go.
Is the trans fluid still nice and red?
Pull the trans pan down and see if you have friction material in the pan / filter.

Yeah the fluid is still reddish clear, also if it is the torque converter how hard is that to replace? Thanks for the help

You will have to pull the transmission to service the TC. The engine can stay in the car, just use a jack and a piece of 2X4 under the pan for support. Its something that can be done in a day. Just use some ramps (or supports high enough to slide the trans out from under the car) and use a floor jack to lower the trans. It helps to have a helper to work the jack while you (or helper) holds the transmission so it stays on the jack to lower and to reinstall.

Many times fresh fluid and a new filter will eliminate the lock up shudder problem. I know that you said your fluid looked good, but you may find it is worth a try. I also recommend going back with ATF+3 type fluid.

"DW"

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If it ain't broke, fix it!

ok will do prob this weakend, Ill try changing the fluid first... Anyway I haven't been able to duplicate the problem...