Clunk when shifting into reverse

[DougDA]

hi
I'm still getting a huge clunk when shifting from Park into Reverse (or even Drive)....

1970 302/C4

I've changed the UJoints but no difference.

Ideas? Trans or rearend?

[Johnnewc]

Hello sir my 1969 f100 with a 302 and c4 transmission does the same thing. I've had the transmission rebuilt. I've also replaced all of my u-joints and it still does it. The ring and pinion are set right. It did it before the 2.91 gears were put in. I personally think its the spider gears that are worn out in my differential. I have 135,000 miles on it. How many miles does your truck have on it?

[jzjames]

I dont know either, my C4 does it also, its probably a good idea to get your idle rpm’s down to the correct range.

[DougDA]

Mine is showing 75K

[fastEdsel]

You may want to check with a reputable transmission repair shop and have your vacuum modulator valve checked. The valve provides for a smooth shift between gears but not sure about reverse. My old FMX transmissions will bang between gears and also into reverse. It's just annoying. If these old Ford's and GM's had the Chrysler Torqueflyte transmissions they could have run away with the markets IMO. Am seriously considering installing a C6 into my Edsel just for that fact. A 4 speed auto update might also be a good choice but with 2:69 rears I might not gain much. The very smooth torque of the big block FE more than makes up for additional gearing. Let us know how you make out with your challenge.