Runs rough in Reverse Gear

[dogmagolf]

'71 440-6 727 Auto. Car idles good (about 850-900 RPM), idles fine in drive (about 750-800 RPM), drives well (besides the late shift issue, posted on another thread). In reverse however, the car seems like it is stumbling a bit, and is also very shaky/rattly. It reminds me of a bad motor mount issue I had in a prior VW - that said, mounts look fine on this car. Is there any different adjustment for the car when it is underload in drive or forward gear as opposed to reverse? The RPMs seem to drop a bit more in reverse gear than forward gears which I think is causing it to feel so shaky, as in the stumbling is shaking the car and creating the extra rattle sounds everywhere.

Looking through the forum it doesn't seem like there is any reverse adjustments that make any difference.

Thanks in advance

.:R

 

[pschlosser]

This *may* be related to the too much throttle pressure discussed in your other thread.

Also, the rally dash tachometer may not be accurate. It's possible the tach reads low and your car is idling higher at 1500-ish RPM, and can cause the symptoms you describe.

If you haven't confirmed the RPM, do you have one of those tune-up meters that shows RPM, dwell, and what not? Like the Craftsman ones Sears used to sell?

If you can, confirm the RPM is below 1000 at idle in park/neutral.

 

[Steve340]

Check the timing and idle fuel mixtures.

 

[dogmagolf]

This *may* be related to the too much throttle pressure discussed in your other thread.

Also, the rally dash tachometer may not be accurate. It's possible the tach reads low and your car is idling higher at 1500-ish RPM, and can cause the symptoms you describe.

If you haven't confirmed the RPM, do you have one of those tune-up meters that shows RPM, dwell, and what not? Like the Craftsman ones Sears used to sell?

If you can, confirm the RPM is below 1000 at idle in park/neutral.

You may be correct that the dash tach is not reading accurately. I do not have a secondary way to check RPMs etc. but is on my list to purchase. I will start getting on that ASAP and see what the actual RPM is. As far as idling higher, you think that it idling above 1000 RPM is worse off than under 1000 RPM? I am curious (just for education) where the higher RPM would cause these symptoms and why.

Thanks again!

.:R

 

[Xcudame]

Higher RPM will make it to be more harsh for certain. Think of this way, which would be harsher on your body, hoping out of a car going 2 mph or one going 20 mph? A little extreme, but you get the idea now.

 

[Chryco Psycho]

The mounts are just a sandwich , they can look ok but are separated , put a jack & 2x4 under the oil pan and lift a little

 

[Xcudame]

True Chryco Physco, the rubber mounts should be checked as well!