Hi All!
I've got a stock '82 with recently replaced lower ball joints. Up until the replacement of the joints, the car rode fine. Now as soon as I slip into 4th gear, the car vibrates - it's not shaking my teeth loose - but it's very noticeable. 5th gear is fine - just 4th. I didn't notice any reduction in vibration when I went between 4th and coasting at the same speed (about 40 mph). The car wasn't aligned after the joints were replaced. Tires are new, about 300 miles ago.
I'll be taking the car in for an alignment next week and would like to be armed with information so I'm not taken unawares.

Many thanks!

 

A good alignment should correct the issue. You might also want to look at getting your tires balanced while you are there.

 

Does it vibrate in all gears at 40 mph or just 4th?

 

Just 4th gear (at any speed). All other gears are fine at any speed.

Thanks, Kentetsu. A question about the alignment. I had one guy at garage tell me that they can't align my type of car, but another guy at the same place said they can. Is there something different about the 1st gen RX's that they need to be aligned at the dealership?

[rant] I've taken my auto to four "recommended" places and have had to take it back several times (each place) to get the work done properly. Things like welding on the wrong muffler or not reconnecting the electrical (no horn?) to blowing fuses to flooding the engine & gunking up the plugs and severing the vacuum line. I just want something done right the first time. [/rant]

Ok, I'm done now.

Thanks!

 

Well, there shouldn't be anything special about aligning your car. I won't say that they're great, but I take my cars to Sears just because if there is a problem they will redo the alignment for free for the next six months.

You might want to try a national tire store though, like discount tire. Chances are, the more they concentrate on stuff like that, the better job they'll do. A small shop that does mostly mechanical repairs might not have the experience needed to do it right.

 

That fourth gear vibration must be transmission related or it would be there in other gears, that is a worry, I'm no expert so check on it with someone more knowledgeable.

Any alignment shop should be able to do your car, its a very simple and normal ball joint front end.

Most mechanics dont understand rotaries (or care to), so buy the manual and do it yourself, save you money and great satisfaction.

 

I have the manual, and I've thought about it, but I'm a desk jockey (webmaster/graphic designer) and I Know I'll royally screw it up to the point where it will cost me more to have someone fix my mistakes!

Thanks for all the good points everyone has taken the time to make! I'll look into all of your suggestions.

 

I hate hearing mechanics say they dont/wont work on RX-7s.
They ONLY mechanical difference of our cars is the internals of the engine.If you have the skills to become a certified mechanic and do it for a living,you should be able to look at a rotaries cooling,fuel and exhaust sytems and be able to understand the minor differences.The rest of the car,brakes,suspension,drivetrain,electrical......i ts all tottally conventional.

4th gear isnt actually a gear.Its just the trans input and output shafts coupled together.1 turn of the engine going into the tranny,comes out as 1 turn of the tranny into driveshaft.There is no reduction and thus no load on the countershaft.Thats why many times,tranny noise problems will GO AWAY in 4th,not get worse in 4th.You might have a mainshaft bearing failing and it only makes itself known in 4th.
It could also be the driveshaft/ujoints,as they are all essencially "one" with the tranny when in 4th gear.....

Since you say it doesnt change when you coast or apply power,Im more inclined to say its an alighnment issue.Driveline vibrations tend to be power "on-off", and road speed dependant and are noticable through the shifter and towards the rea of the car.