It's been awhile since I've posted here bc I've been out of the rotary game for awhile. I found a '88 vert on Craigslist that i'm interested in. The car is super clean....Took it for a "test drive" in a small business park (got it up to maybe 10mph in 2nd gear max)....During the quick drive, I noticed a thumping sound....Seemed intermittent. I couldn't figure out how to replicate it. I recently sold my 99 Miata. In that car, whenever I would let off the clutch quickly, I would hear a similar sound. This FC seems to make that sound randomly just cruising at low speeds. Any idea what this could be? Thanks.

 

Probably driveshaft u-joints.

 

Makes sense...Thanks for the advice. I'll use this to help negotiate the price down a bit. Wish me luck!

 

could also be a Front diff mount on its way out too.

 

Would the diff mount cause clunking while cruising at very low speeds? I did read elsewhere that these front diff mounts are prone to failure.

 

Best way to diagnose is to look under the car before throwing parts at it. Driveshaft and front diff bushing should be obvious pass or fail

 

If you're not giving it a lot of throttle, the slack in the drivetrain could ba making it thump. To check it, get under the car and grab the rear of the driveshaft. Push up and down- if it moves, you need to replace the front diff mount. Not too bad of a job if you have a few jacks and an hour or 2.

If it is indeed that mount thats broken, look into adding a pinion snubber when/if you replace it.