Transmission issues

[Vader73]

Hi folks. I own a 1990 gmc 2500 4x4 with what I'm assuming is a Muncie SM465 4spd trans. The problem I'm having is that I have L and 1st, but can't put it into 2nd, 3rd or reverse. I drained the oil with no metal present and refilled with new, but no dice. I'm guessing either shift fork bent or synchros??

Any ideas?

TIA

[Mikebtte]

Remove the rubber boot around the bottom of the shifter, remove the shifter from the transmission. Look at the shifter handle and down into the spot were that shifter sits. Make sure its all in place and not bent. If that is strait disassembling the transmission for a closer look may need to be done. 

This is a good place to start.

 

Should look like the pictures below.

 

[Vader73]

Mine looks a little different. Cast iron case with an aluminum top cover....

Also, would it be worth prying the knockout on the trans tunnel to access the top cover? I was told the trans has to be in reverse to remove the top.....?

[Vader73]

[Black02Silverado]

Considering the age it might be your best bet to rebuild it.  From what I can tell it isn't hard.  How many miles are on it?

[Mikebtte]

Sometimes that cup gets worn out and the shifter pops in and out.

I have never had to put one in reverse to remove it.

Rebuild would be an easy job.

You can remove the 4 bolts on the tower and see down inside. You might be able to see if a fork is bent. They don't bend often. Prolly wore the teeth off a gear.

Get that top off and you should be able to tell.