Hi guys
i have 90 honda civic hatch with a b16a and my 5th keeps popping out its started with a grind noise when i would press on the gas now it pops. My mechanic said it was from my rear sub frame being cracked.

 

Great question! Let me see if I can help you.

Wait... there is no question.


sounds like your rear subframe needs to be fixed or you need a new car/shell.

 

But could the rear sub frame being crack cause my 5th gear to pop out??

 

I had a bad syncro when I was experiencing the same issue.

 

the engine and transmission are held in place by 4 mounts, one on either side of the car and then one on the front and back.
The ones located on the front and back are subjected to a lot of the twisting motion from the engine torquing.

If the rear subframe is broken enough, the transmission can then twist beyond normal.
The shift linkage is then compromised and allows for the gear to be popped out during driving.

I'm surprised that you are not having problems with 1st and 3rd as well.

 

My money is on the transmission. If it were the subframe you would be having many more problems than just with 5th gear.... I had an Ef with a stock D series mount on the subframe held in with 1 bolt on the backside. It had tore the mount up and my engine flopped the fuckaround, banged the firewall and it ALWAYS went into gear. Is the subframe your problem with 5th gear? Doubt it, But if you truely do have a cracked subframe that is a whole other problem and you need to remedy the issue before bad things really happen.

 

Start with the easiest, simplest things first. Before you do anything else check the fluid level.



Pull the fill plug, and if no fluid comes out, or if you dip your finger into the hole and cannot get any fluid on your finger, then you need to add fluid. 5th is the last to get the oil bath, and can pop out if it's not being lubricated. I'd suggest a drain and refill if your trans is currently low on fluid - the fluid is probably nasty.

Outside of that it sounds like you've got other issues such as engine/trans shifting/alignment if your rear subframe is busted, and allowing for excessive movements.