3rd gear no power and shaking?!? transmission issues

[IceCold240]

Okay, I have two issues which I'm hoping you gurus can shed some light for me. It's a '92 240sx, my first manual car (yay learning to drive manual) and 240.

1st issue is, when I get into third gear, I have some serious shaking going on. It feels like engine is transmitting a lot of extra vibration into the cabin. This is like around 40-50mph, and at 1500 or so rpms. It shakes when I give it some gas, but then when off throttle. It stops shaking once I get passed 2500-3000 rpms. In other gears, it doesn't have this issue.

2nd issue is, third gear feels reallly slow and low power. I mean, 1st and 2nd feels right at WOT, but when I get into third, it's dog slow at revving up compared to how 1st and 2nd were. I'll shift around 3500rpms to 4th gear, and it feels like 4th gear is pulling harder then 3rd, as well as revving up faster. It doesn't look like the clutch is slipping, cause the rpms aren't jumping, but in third gear rpms rise slower then 4th gear does.

So any ideas on what could be causing these issues? Thanks in advance!

[navysnail]

try shifting later, keep it over 2000 or it will shake, just the way stick works, maby there is a problem in the gear itself, i dont know why it would not pull in 3rd except that you are out of the power band.

[IceCold240]

Well for normal driving i'm shift at around 3500-4000rpms. When I hit third it's around 1250-1750rpms which doesn't seem too low from the sound of the engine. It's not a bogging shake either, more of a constant vibration that builds up.

[navysnail]

sounds like a problem in the transmission or possibly speed related. if your in a different gear going the same speed as third does at 1250-1750rpm, does it happen? if it does, try balancing the driveshaft

[DAN510]

don't want to sound stoopid but....

are you sure your not hitting 5th maybe.......

the way your descrition reads, it almost sounds that way,:thinker

I'm in no way saying that you can't drive or anything like that, try running your shift pattern at a stand still and keep it closer to first when your pushing up to third......

later DAN510:ylsuper

[BoyWonder]

Yeah it does sound more like from 2nd to 5th, cause from 4000ish RPMs to 1750.. that seems like a heck of an RPM drop. Easy test would be to see what speed you're going at 4000 rpms in "3rd". That'd tell ya real quick if it really was 3rd or if it was in fact 5th. Still, I think you'd notice when you went into 4th if you had to move the shifter laterally, so I don't know. Like he said, practice at a stand still. Maybe have someone else give it a drive who has driven more than one manual car, and see if they have the same opinion.

[BoyWonder]

Yeah, I just double checked my sanity. Should only drop from 4000 to right below 3000 (like 2.8kish)