Drivetrain Groaning/low pitched grind noise on downshift AOD

[bruno]

91 GT, AOD, 250k miles

Backstory: Transmission started making loud clunking noise when I put her in gear, and on deceleration it would make an odd scraping sound. The transmission was original and not rebuilt. With over 250k miles on it a full rebuild made sense.

With the rebuild we also swapped out the original 2.73 gears for 3.27. (in case that info matters). The scraping sound is gone, but there is still an slight groaning with low pitched grind sound that happens on deceleration. I'm so effin' frustrated, and feel like i'm just burning money. Am I expecting too much from this older AOD tech? Is there some noise to be expected?

Hope someone has come across something like this before.

Thanks in advance.

Bruno

p.s. - I have to say, I thought the difference was going to be more from a 2.73 to a 3.27 gear. Bummer, live and learn I guess.

 

[General karthief]

Transmission shop do the rebuild?

 

[bruno]

Yep, my mechanic sent it to a transmission shop he likes. And I trust my mechanic.

He hears the noise as well, but thinks it's normal. Previously, right after the rebuild, it made a louder sound on decel. So he had the guy open the transmission up a second time and replace all the bearings once more. He said they both looked it over and saw a slight mark on the main shaft. Transmission guy said his manual said to mil some off the shaft, then grind a cross at end of shift for better lubrication.

I'm still hearing the decel sound, and was hoping someone has run across this to help mechanic fix it.

 

[General karthief]

That sound is a cry for help, the trans should make no noise at all.
i would get a second opinion. Never heard of milling anything or adding a cross on the shaft for better lubrication

 

[bruno]

OK, thanks for the reply kartheif.

I've seen the cross modification on an upgrade sheet by @SilverFoxbody ; otherwise hadn't heard of it. The milling, I've never heard of.