Maybe this will help - https://forums.fordthunderbirdforum.com/threads/1957-automatic-reverse-clunking.18317/

HIGH IDLE
ENGINE/TRANS MOUNTS
U-JOINT(s) - YOKE - REAR FLANGE
PINION GEAR WRAP-UP

Further explanations in attached post.

As for throttle adjustments, there are three, pedal height, carb linkage and finally TV linkage which cannot be adjusted correctly before the first two.

All linkages/bushings must be good.

How long has it been since serviced with bands adjustments? Fluid service?

Finding someone now who you can trust to work on one is a long shot.

You need a WSM (and TRANS MANUAL) to go about it properly.

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All the replies have been very welcome.
Just to try to explain this better, which I am not good at?
I have a tach in the car, the idle is down to 500 after starting and before shifting into reverse.
The car shifts well going forward, shifts very smoothly at 2000.
The car does not slam after sitting when I shift into Drive.
It only shifts-slams (always) when shifting into reverse,
Is there a chance the linkage between the gear shift handle in the car and the control going into the transmission is not adjusted correctly.
     Might it not be totally engaging thus the slam.
My other Y block car is a 57 see my Profile. shifts very smoothly into reverse.
thanks again for all the help.  Harold

Adjusted

Has anyone djusted the linkage, speciacally the linkage that has the u Bolt?

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The PCV should not be vented into Air Cleaner. Preferred place is the Carburetor if equipped for PCV or spacer Plate under Carb. PCV is supposed to take Fumes from Engie and re-burn through Intake-NOT the Air Cleaner. Hooked up to Air Cleaner is sucking in Air like a big Vacuum leak. Air Cleaner could be hooked up to Oil Fill Cap to introduce filtered Air into Crankcase for a closed PCV System. Likely why it won't Idle properly..

  

Does it slam the most when you start it cold and the choke is set and backing out of the garage? How is it when the engine is fully warmed up?  Could be that the higher RPM is causing it.r .  Doesn't sound like a trans problem to me.  Otherwise, does the trans work OK ?





54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

You need the correct year WSM to do all you want to do (IMO).

I have used them since 1966.

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Thanks for getting back to me. Yes, still slams. 500 RPM, the car has a tach.Are you suggesting that I get the For Manual? Have you used it? Thanks. 

It is still slamming when put into reverse?

What is your RPM while in gear (need tach)?

Have you checked the trans mount, u-joints and watched for pinion wrap-up?

You shouldn't have to pull the engine/trans, just the trans.

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