Vacuum Lines/Transmission Relationship?
Thread Starter
Senior Member
True Car Nut
Joined: Mar 2005
Posts: 2,689
Likes: 0
Vacuum Lines/Transmission Relationship?
This quote is from another post and it got me thinking...
http://www.bonnevilleclub.com/forum/...r=asc&start=20
I know the rubber connections on my vac lines are starting to dry out and crack - I'll be replacing them soon regardless. Not sure if it'* related, but at light to medium light throttle the shifts have started to become a little rougher - nothing major but definitely not silky like they were just a few months ago. I don't pound on the car whatsoever and I did the trans fluid and filter less than 12k ago. Fluid is still nice and pink. I have a 4T60-E I believe and the "E" would lead me to think it'* totally electronically controlled but that comment above made me wonder! zeroburnz has a '97 SE as well.
What'* the deal? Should I also check the transmission solenoid for it sticking? Thanks
http://www.bonnevilleclub.com/forum/...r=asc&start=20
Originally Posted by zeroburnz
Hey guys. Replaced all the vacuum connections down by the evap. canister and some others that looked like they needed replacing. Have noticed that my rpms at idle have smoothed out a little and no more jerking when the transmission shifts. I am however still getting the misfire code on cylinder 3. Other suggestions?
What'* the deal? Should I also check the transmission solenoid for it sticking? Thanks
DINOSAURUS BOOSTUS
Expert Gearhead
Joined: Mar 2005
Posts: 41,391
Likes: 30
From: Enfield, CT
Vac leaks effect your performance and that could effect how a shift feels..
The original author was probably a 4T60 transmission that is controlled by vacuum, whereas your 97 is fully electronic controlled.
The original author was probably a 4T60 transmission that is controlled by vacuum, whereas your 97 is fully electronic controlled.
Senior Member
True Car Nut
Joined: Jun 2004
Posts: 3,459
Likes: 1
From: Glendale, AZ
Dame is right...
The 4T60-E is mostly controlled by the PCM. However, vacuum controls the firmness of the shifts (I'm not sure if "line pressure" is the correct terminology, but we'll go with it). If you completely disconnect your vacuum lines the transmission will shift really hard, which is the same thing that happens if you have a vacuum leak or have the vacuum modulator adjusted to allow only slight vacuum pressure (like mine
). If your vac lines are compromised, your shifting line pressure will go up, causing more "jerky" shifts.
This is the reason why aftermarket parts companies advertise "higher shifting line pressure" adjustments to their PCMs, but the effect isn't felt in '97 L36 Bonnies (L67 Bonnies from '97 had the 4T65-E). The only way to change shift firmness in a 4T60-E is to reduce vacuum or install a shift kit. Line pressure is totally independent of the PCM, unlike a 4T65-E, which is fully electronic.
The 4T60-E is mostly controlled by the PCM. However, vacuum controls the firmness of the shifts (I'm not sure if "line pressure" is the correct terminology, but we'll go with it). If you completely disconnect your vacuum lines the transmission will shift really hard, which is the same thing that happens if you have a vacuum leak or have the vacuum modulator adjusted to allow only slight vacuum pressure (like mine
). If your vac lines are compromised, your shifting line pressure will go up, causing more "jerky" shifts.This is the reason why aftermarket parts companies advertise "higher shifting line pressure" adjustments to their PCMs, but the effect isn't felt in '97 L36 Bonnies (L67 Bonnies from '97 had the 4T65-E). The only way to change shift firmness in a 4T60-E is to reduce vacuum or install a shift kit. Line pressure is totally independent of the PCM, unlike a 4T65-E, which is fully electronic.
Thread
Thread Starter
Forum
Replies
Last Post
brminder
Performance, Brainstorming & Tuning
2
Dec 23, 2002 05:03 AM