Automatic Transmission Problems

[1997GTJF]

Hi guys , I've started having problems with my automatic transmission on my 2000 GT 4.6 V8.

When accelerating it shifts into 2nd perfect but it doesn't seem to like shifting into 3rd under load, as soon as you come off the throttle it then changes into 3rd ok, but on the throttle it will just stay in 2nd gear.

The strange thing is it goes into 3rd gear after kicking down ok but it's just the initial first time you accelerate it doesn't under load

Could it be the vacuum modulator ?

I've checked the fluid and the level seems ok , fluid looks a pink/red colour still and it doesn't smell of burning or anything.

The car has done 114k miles but I thought the transmission should have lasted a lot longer than that ?

Thanks for any help.

 

[1997GTJF]

Quick update , it seems to be the overdrive that is causing the problem , I switched the overdrive off when I drove it this morning and it seems ok but as soon as it's turned on I think everytime the car tries to shift into overdrive its slipping out of gear .

Any ideas ? Thanks

 

[Cobra42898]

I would start with a fresh drain of the fluid, including dropping the pan and changing the filter, and drain the TC if it has a plug. Refill with Mercon v, not the regular Mercon. The difference is important. Don't take it somewhere and do one of those flush deals. Full drain, full refill.