1995 grand am 3.1L transmission problem

The transmission on my 1995 grand am with a 3.1L upshifts fine. When it downshifts from 2nd to 1st it slips. It sounds as though I'm braking on a patch of loose gravel. This problem is intermittent but occurs every day. On the same car...occationally when starting & more often when reving the engine above 2000 rpm when in park or neutral, a loud clunking/popping sound is present. This sound completely dissapears when in gear. Are the two problems related? The dealer suggested replacing the transmission & they would be happy to do so for $2500. I am a moderate shade-tree mechanic but this has me stumped. Any insight would be greatly appreciated! Thanks!

I also have a 95 pontiac grand am GT and when in park or neutral when you rev it it makes a popping noise and then when stoping to downshift from 2nd to first it makes a big cluncking noise. the noise will start quiet then get really fierce. its like im almost jumping. My mechanic said the cluncking noise in park was because of a belt inside of the transmission slipping and the reason why it doesnt do it in drive is because there is tension on it. I would really like to know if these 2 things have anything in common.

also do you have any idea what speed that transmission is?

It is a 4 speed 4T60E transaxle. I replaced the fluid & filter & checked for debris and found none. The clunking into 1st gear on the downshift is now more like the hard clunking you describe. I am looking into the possibility of a faulty TCC sensor. Anyone with some input...please advise!!

turns out after all i had to get the transmission replaced. i bought a used transmission for 800$ with labor included. sorry about the bad news

Dude I use to own a red 1995 Grand am GT I had the same proble you did. at first I thought it was solinoid sensor, but as I dug a little more it was my 2nd and 3rd gear. My teeth on these gears were borken which cause the car rev up more and skip gears (clunking noise) I took my to Ammco transmission and got it fixed for $1100.00. if it is not one of 2 problems I would say replace the whole thing.