Transmission Shifting Erratically
Thread Starter
|
New User
Joined: Oct 2004
Posts: 5
Likes: 0
Transmission Shifting Erratically
I am a new owner of an 1988 Bronco II. I have recently noticed that on the highway at various speeds, the transmission will downshift for no apparrent reason and then after a few seconds, shift to a higher gear. I have a friend who told me it was my modulator but I do not know where it is or how to replace it. (Or for that matter if the modulator is the problem)
What should I expect to pay for the modulator and how do I determine if this is the problem?
Thanks in advance
THP
What should I expect to pay for the modulator and how do I determine if this is the problem?
Thanks in advance
THP
Postmaster
Joined: Dec 2001
Posts: 3,742
Likes: 2
From: UT
Vacuum modulator controls 1-2 and 2-3 shifts on an '88 A4LD. EEC-IV computer controls 3-4 shift and torque converter clutch (TCC) lockup. In order to determine if the modulator is potentially the problem, you would first need to determine which shift is effected. If it's dropping from 4 to 3 or the TCC is unlocking unnecessarily, I would start be checking the EEC-IV system. If it's dropping from 3rd or 4th to 2nd, that could be vacuum modulator or some other hydraulic or mechanical fault.
Thread Starter
|
New User
Joined: Oct 2004
Posts: 5
Likes: 0
OK, now I must ask, what is the EEC-IV and how do I check it to confirm that it is acting improperly? Also, where is the vacuum modulator on the transmission?
I notice that this problem is most pronounced when I am at around 60 mph on a hwy, which would indicate a problem between 4-3 and an EEC-IV issue. However, I do have some problems, albeit not so pronounced in the lower gears.
If you could point me to the modulator, I believe I will check this component out first since it appears to be happening throughout the gears.
I notice that this problem is most pronounced when I am at around 60 mph on a hwy, which would indicate a problem between 4-3 and an EEC-IV issue. However, I do have some problems, albeit not so pronounced in the lower gears.
If you could point me to the modulator, I believe I will check this component out first since it appears to be happening throughout the gears.
Postmaster
Joined: Dec 2001
Posts: 3,742
Likes: 2
From: UT
Vacuum modulator bolts to the side of the transmission next to the catalytic converter, so it's kind of a pain to get to. Usual first check of the modulator is to check the vacuum hose for ATF, most easily done at the vacuum tree at the rear of the upper intake manifold.
EEC-IV stands for Electronic Engine Controls - 4th generation. Basically, the engine and powertrain control system used from early to mid '80's through '95. 1st step in checking the EEC-IV system is to perform the self-tests (aka pull codes). See "pulling EEC-IV codes" in Ken00's tech info post.
EEC-IV stands for Electronic Engine Controls - 4th generation. Basically, the engine and powertrain control system used from early to mid '80's through '95. 1st step in checking the EEC-IV system is to perform the self-tests (aka pull codes). See "pulling EEC-IV codes" in Ken00's tech info post.
Thread
Thread Starter
Forum
Replies
Last Post
