Strange vibration at 38 mph, like washboard
 

A while ago, I posted on a strange vibration issue here: https://www.civicforums.com/forums/3...35-40-mph.html It was successfully resolved by replacing the control arm bushings. I am now having similar vibration issues.

Two weeks ago, I had my indy replace a left front spring. He then replaced my belts (due to squealing) and valve cover gasket to following week. Shortly thereafter, this vibration occurred. It is primarily a loud audible sound but can be felt in the steering wheel and pedals. It sounds and feels exactly like you are driving over washboard on a dirt road. It only occurs when driving straight ahead, with you foot on the gas and only at 38-39 mph. It seems to need a bump in the road to start the sound. But as soon as you let off the gas or change speeds, it stops.

My indy rechecked everything and could not isolate the cause of the problem. Since the bushing and CV joints are relatively new, that's not the cause of the issue. It's not really a wheel balance issue as the vibration is fairly loud at a specific speed. It doesn't sound like bearings as it only occurs when driving straight. I am wondering if this vibration is related to the spring replacement.

Any thoughts or ideas would be greatly appreciated.

Re: Strange vibration at 38 mph, like washboard
 

post a video.....with sound

Re: Strange vibration at 38 mph, like washboard
 

It's near impossible to make a video. The vibration and sound happens infrequently. It only happens at 38-39 mph but doesn't always happen when driving at 38-39 mph.

Re: Strange vibration at 38 mph, like washboard
 

checkall nuts & bolts on a arm

check all motor mounts for wear

rotate front tires to rear to see if it follows a tire

check cv joints & wheel bearings

Re: Strange vibration at 38 mph, like washboard
 

Thanx. I am suspecting that it could be the motor mounts too. I will check those out.

Re: Strange vibration at 38 mph, like washboard - FIXED!
 

It looks like I have fixed the problem. While searching this forum, I found these threads which discuss a very similar problem:

https://www.civicforums.com/forums/3...-rpm-help.html

https://www.civicforums.com/forums/3...28-40-mph.html

The similarity in symptoms was very close. So I started driving in D2 and could not recreate my vibrations. If I switched to D, the vibrations returned. This eliminated suspension as the culprit and indicated that it had something to do with the RPMs or the tranny. So I changed up my ATF (using Honda ATF) and the symptoms have vanished! I have another 3 qts and will change it up again next week. Keeping my fingers crossed this is a permanent fix.

Thank you for your assistance!!!

Re: Strange vibration at 38 mph, like washboard
 

These are symptoms of "Torque Converter Shudder" and can be fixed by doing a tranny fluid drain through the drain bolt and refilled with 2.9 new quarts of Honda Brand ATF from dealer. Shaking stopped after that. Look up the proper way to do it & try it out, it's a cheap fix.