What is normal TC slip
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New User
Joined: Oct 2006
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What is normal TC slip
My 99 automatic seems to slip more than I like. I did have the Ford Dealer Tech drive with me with his diagnostic computer plugged in and he said that the slip was within nomal range. I get about a 300 to 400 rpm change when I feel the torque converter lock. also it would seem from one logic point that it would slip more when under a larger load but when I increase the throttle the TC has more of a tendancy to lock up. I would assume this is due to higher pressure in the transmission? I have 100K on the truck and it runs great. To this point I only have an AFE stage 2, and am looking towards gauges, 4" and dp tunes. probably in that order. I don't drive hard and only tow about 5K rarely. is a valve body in order or will tunes increase pressure and solve my concern? Or do I really have a concern?
Posting Guru
Joined: Jul 2003
Posts: 2,210
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You don't have a concern. That amount of slip is normal. If you were heavily loaded and unlocked, expect to see about 1000 RPM slip.
The torque converter locks when the computer tells it to. It doesn't rely on pressures changing with speed or pedal position, it's all computer controlled.
If you want to spend money and reduce the amount of slip, buy an aftermarket lower stall torque converter.
The torque converter locks when the computer tells it to. It doesn't rely on pressures changing with speed or pedal position, it's all computer controlled.
If you want to spend money and reduce the amount of slip, buy an aftermarket lower stall torque converter.
Post Fiend
Joined: Sep 2006
Posts: 7,426
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From: Sioux Falls, SD
A valve body will be in order. Ask DP when you buy the chip and they will recommend the valve body upgrade. Jon Faubion (Faubion Motorsports) built mine I could pass on his # if you like.
Some programmers/tuners increase the line pressure in your tranny and this is no good over time.
Some programmers/tuners increase the line pressure in your tranny and this is no good over time.
Senior User
Joined: Oct 2004
Posts: 420
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From: Bonney Lake, WA
This my be a dume question, but Iv just never really understood or known what to feel for but,
1. What does it feel like when your auto trans starts to slip?
2. What does it feel like when your TQ locks up?
1. What does it feel like when your auto trans starts to slip?
2. What does it feel like when your TQ locks up?
Post Fiend
Joined: Sep 2006
Posts: 7,426
Likes: 6
From: Sioux Falls, SD
Originally Posted by wolfe1104
This my be a dume question, but Iv just never really understood or known what to feel for but,
1. What does it feel like when your auto trans starts to slip?
2. What does it feel like when your TQ locks up?
1. What does it feel like when your auto trans starts to slip?
2. What does it feel like when your TQ locks up?
The changes/shift in gears you feel while you are driving go in this order.
1st
2nd
3rd
Torque converter locking
then OD
The Torque converter locking feels like a shift in gears.
Post Fiend
Joined: Jul 2005
Posts: 14,582
Likes: 12
From: 21791
At any time the TC is unlocked while driving(accelerating), you can blip or jab at the throttle, and the revs will increase quickly and you won't feel the acceleration push you back in your seat. When the TC is locked, it feels as if it's a manual tranny in gear, and when you blip the throttle the engine speed does not accelerate fast, however you get the feeling of the torque pushing you back in the seat. There is very very little slippage when the TC is locked.
