99 GT Auto Trans Problem
02-22-2009, 09:05 PM
#1
4th Gear Member
Thread Starter
Join Date: Jul 2003
Location: Texas
Posts: 1,003
99 GT Auto Trans Problem
alright the car is at about 64000miles when im driving the car seems like it downshifts and the rpms sit a little higher than they need to be. after sitting high for a little bit it shifts back. i tried cleaning the IAC so not sure that its the problems or not. any help would be great.
02-23-2009, 08:13 PM
#6
1st Gear Member
Join Date: Jan 2009
Location: North Carolina
Posts: 132
The converters are notorious for locking and unlocking randomly on the stock tune, especially as the mileage gets up there, and the fluid gets old.
2 things that really help it:
Changing all the transmission fluid, this includes draining the converter, which normally doesn't get done with a fluid change. It takes about 12 quarts if I'm remembering right.
Update the tune with a better converter lockup schedule.
2 things that really help it:
Changing all the transmission fluid, this includes draining the converter, which normally doesn't get done with a fluid change. It takes about 12 quarts if I'm remembering right.
Update the tune with a better converter lockup schedule.
02-23-2009, 08:40 PM
#7
2nd Gear Member
Join Date: May 2008
Location:
Posts: 288
with 64000 i would say just have a trans flush done, about $120 at my shop, cant imagine much more/less elsewhere. thats gonna pump 16 quarts of clean trans fluid thru trans, converter, pump, lines and even the cooler. that and like mentioned above get reflashed.
02-23-2009, 10:43 PM
#8
4th Gear Member
Join Date: Jan 2006
Location:
Posts: 1,143
imo what youre perceiving is the torque converter unlocking, and then locking.
say youre going 40 and youre at 1250 rpms, you press the gas in a little and the rpms jump up to 1850-2000 and then go back down to 1250ish.
With a tune my converter stays locked unless I really get into it, which I like, unlike the tap the gas too hard and its unlocked stock tune.
say youre going 40 and youre at 1250 rpms, you press the gas in a little and the rpms jump up to 1850-2000 and then go back down to 1250ish.
With a tune my converter stays locked unless I really get into it, which I like, unlike the tap the gas too hard and its unlocked stock tune.
02-24-2009, 08:58 AM
#10
1st Gear Member
Join Date: Nov 2008
Location: Indiana
Posts: 62
Also be forewarned not to use a non custom programmer to firm up the shifts - Thats why I had to have my trans rebuilt 
Custom tuners are better but you still do not want to increase the line pressure to lock the clutch packs = DUN - DONE. Use a shift kit, change the tranny fluid and she should be fine.
Custom tuners are better but you still do not want to increase the line pressure to lock the clutch packs = DUN - DONE. Use a shift kit, change the tranny fluid and she should be fine.
Last edited by Agentl074; 02-24-2009 at 09:05 AM.