904 Reverse Thunk

[gyxffyg]

My 1968 Barracuda with 904 automatic has started having an abrupt "thunk" when I go into reverse. Goes into drive with no problem. It was low on tranny fluid so I toped it off but have not really driven it since I did. Have only had it for a couple of months and not sure what type fluid the po put in the tranny, although he said synthetic. Will be changing out the fluid soon just so I know what is in there. And it shifts through the gears with no problem. I have read on hear that sometimes this may be caused by bad u-joints but the po said he put new u-joints in less than 15k miles ago. What would cause this?

 

[Woods74]

It being a manly transmission, shifted by a man, doing man s*it. Let it go.

 

[Locomotion]

Not saying anyone lied, but it never hurts to double check things regardless of what someone says. U-joints, straps, trans mount, ring & pinion backlash, etc. You might even find something the previous owner wasn't aware of and have peace-of-mind in the end. I don't know enough about trans internals to speculate there.

 

[TrailBeast]

Not saying anyone lied, but it never hurts to double check things regardless of what someone says. U-joints, straps, trans mount, ring & pinion backlash, etc. You might even find something the previous owner wasn't aware of and have peace-of-mind in the end. I don't know enough about trans internals to speculate there.

X2
You might take a look at the rear band adjustment also.

 

[gyxffyg]

Any thoughts on the best way to check U-joints

 

[moe7404]

like my friends said check the bands, and U-Joints. all so to get by till; its fixed try pulling the lever to low first then rev. going straight to rev throws about 300 psi to the servo. all at once. by going to low you load the servo with about 100 or so first the an other 100 or so.

 

[Bad Sport]

I have read on hear that sometimes this may be caused by bad u-joints but the po said he put new u-joints in less than 15k miles ago. What would cause this?

Sounds like it could be the infamous 7 1/4 clunk.

I've had many a car that would clunk going into reverse.