I have a muffled clank coming from the transmission area

[Guest iskone]

At first I thought (hoped) it was my exhaust but it only seems to happen in fith gear.

I have a 78 280Z with a five speed.

Can anybody help me figure out the problem?

It doesn't clank all the time just when I step on the gas hard and it doesn't always clank.

 

Thanks

[datsunlover]

If it only happens in 5th, and only whe you stomp tha gas, I would guess something is toasted in the gearbox.. maybe a bearing or something..

[Guest iskone]

well I can get it to happen when I mash more often, somtimes I don't need to floor it.

Looks like I'll have to drop it and take a look, I keep hoping it's my clutch or pressure plate, but probally not

[datsunlover]

Yah I think if it was anything to do with the clutch, it would happen in any gear, and more often... if you hold your hand on the shifter when the noise happens, can you feel anything (vibration, shaking) through the shifter? Maybe a shift fork is bent/worn? I dono.. All my previous Z's made so many clunks and rattles I couldn't tell what came from where... I gave up and just lived with clunks and weird noises.

[technicalninja]

Early 5 speeds have a problem with main shaft lock nuts loosening up, comingoff and allowing the 5th gear to "walk" up and down the shaft. Nissan first changed the threads to left hand then added roll pin for the 5th gear thrust plate (originally had small ball bearing to locate thrust plate). Often times a early 5 speed with this problem will have this small ball bearing stuck to the drain plug magnet when you pull tranny drain plug. I have been able to fix some of the trannys that had this problem I've seen but usually it is cheaper to get a junkyard tranny. Get as late a tranny as you can as the late 82 and all 83 5spds seem to have both upgrades to the mainshaft. The left handed threads tend to tighten as the tranny is used instead of loosen. All versions have the lock nut "peened" into the mainshaft but the change of thrust that this part sees rocks the nut back and forth and removes the peening after time. Increasing power out put of engine causes this to happen sooner. My technique of refitting old style main nut is to use new Nissan nut, torque to high end of range, and peen the nut to the shaft as deep as I can go. Use red lock tight also.

Ive never had to take one off after doing this but I feel sorry for the guy that does.

This may have nothing to do with your problem. If you cannot find problem with clutch or mounts (check rear end mount also) then take back case off of trans and check play of 5th gear. Grab last gear on main shaft and try to move it back and forth. It should not move more that .004". Ive seen some where gear had been moving back and forth on shaft 1.5 to 2 inches which destroyed gear and shaft. This tranny had strange clunk noises when engaging 5th (more noticable under hard shifts).

Good luck

Rick

[datsunlover]

Good post there ninja! I was hoping someone would jump in with more knowlege than me. I understand the principal, but have never taken a standard shift trans apart, so I couldn't really trouble shoot this problem very well.

[Guest iskone]

Thaks for the help guys.

 

I've been hold the shifter every time I hear it but I can't really feel anything, somtimes I might feel the slightest vibration but it could just be me thinking I feel something.

 

Today I heard the noise breifly in 3rd.

I was planning to pull the plug this weekend and check the gear oil level but my roomate broke my jack

 

I've been looking for a new tranny already (just in case) but I still havn't found one. I've looked at rebuild kits too, but I think buying a used one would be better.

 

Can I take the back case off the tranny with it mounted in place?

I can't seem to find my manual or I wouldn't ask about remove the back case.