Trans vacuum modulator
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Laughing Gas
Joined: Mar 2016
Posts: 757
Likes: 43
From: Cheyenne, Wy
Trans vacuum modulator
79 scab 4x4 C6. Picking up from the shop. Has the black stripe modulator. Still shifts SOFT. Turned the black mod all the way in and still soft. I told them to build it for 10-12K lb towing. It should shift much firmer. When getting on it can almost (barely) feel it shift. What's wrong? They say going to a green stripe will help firm the shift. Yes/no?
Thanks for the help. I do not want to sign off until it is correct.
Thanks for the help. I do not want to sign off until it is correct.
Thread Starter
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Laughing Gas
Joined: Mar 2016
Posts: 757
Likes: 43
From: Cheyenne, Wy
Detail list
See anything missing or should have had? Anything here that might explain why it is shifting so slow and the rpm's climb between shifts. Thanks for the help.
Won't even spin the tires in the dirt alley.
Laughing Gas
Joined: Dec 2020
Posts: 869
Likes: 186
From: Near my truck
11 hours to remove, rebuild, and replace is sufficient time to do a thorough job.
The parts listed imply a comprehensive rebuild was done.
Only one band was replaced. (Pure observation and curiosity.)
No sign of a new oil ring for the manual shift shaft. (The oil ring on the outside of the case.)
A shift kit is reflected on the invoice, so one can assume it was fitted.
Even if the C6 originally required Type F, Mercon V should be fine with the new internals.
That said, I'm not familiar with the quality of Fram ATF.
I suspect a torque converter issue, or an installation issue (human error.)
I'd be inclined to return to the shop and ask them for their diagnosis and correction.
Is a large capacity ATF cooler fitted ?
I'd consider temp and pressure gauges. Very useful to have and observe whilst driving.
The parts listed imply a comprehensive rebuild was done.
Only one band was replaced. (Pure observation and curiosity.)
No sign of a new oil ring for the manual shift shaft. (The oil ring on the outside of the case.)
A shift kit is reflected on the invoice, so one can assume it was fitted.
Even if the C6 originally required Type F, Mercon V should be fine with the new internals.
That said, I'm not familiar with the quality of Fram ATF.
I suspect a torque converter issue, or an installation issue (human error.)
I'd be inclined to return to the shop and ask them for their diagnosis and correction.
Is a large capacity ATF cooler fitted ?
I'd consider temp and pressure gauges. Very useful to have and observe whilst driving.
Logistics Pro
Joined: Mar 2002
Posts: 3,881
Likes: 84
From: Wake Forest, NC
C6 only has one band
Its in the overhaul kit
a 79 c6 used mercon, there was a different ford spec for it but thats what it was
Agree
No sign of a new oil ring for the manual shift shaft. (The oil ring on the outside of the case.)
Even if the C6 originally required Type F, Mercon V should be fine with the new internals.
That said, I'm not familiar with the quality of Fram ATF.
That said, I'm not familiar with the quality of Fram ATF.
I suspect a torque converter issue, or an installation issue (human error.)
I'd be inclined to return to the shop and ask them for their diagnosis and correction.
I'd be inclined to return to the shop and ask them for their diagnosis and correction.
Logistics Pro
Joined: Mar 2002
Posts: 3,881
Likes: 84
From: Wake Forest, NC
if so, they need to make it right. Something is wrong. Possibly affecting main line pressure. I'd ask them to put a pressure gauge on it and run it on the lift and see what the pressures look like. You can also run it on the road eith that hooked up and get an idea of where it is. I'd have to look up specs as they're not committed to memory.
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Laughing Gas
Joined: Mar 2016
Posts: 757
Likes: 43
From: Cheyenne, Wy
Well the shop is working on it today. They say changing to a green stripe will help. One of my customers is a retired master mechanic (he's 72) said it sounds like the line pressure is not high enough. Hopefully the shop calls today. Any thoughts?
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Laughing Gas
Joined: Dec 2020
Posts: 869
Likes: 186
From: Near my truck
I also don't think that the modulator is the issue.
It is more likely to be something 'silly' like not paying attention when swapping in the shift kit parts.
I hope they fix it for you and don't come with BS excuses.
Thank you Aldridgec for correcting my comments. Now that you mention it, of course there's only one band in the C6. Duh !
It is more likely to be something 'silly' like not paying attention when swapping in the shift kit parts.
I hope they fix it for you and don't come with BS excuses.
Thank you Aldridgec for correcting my comments. Now that you mention it, of course there's only one band in the C6. Duh !
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Laughing Gas
Joined: Mar 2016
Posts: 757
Likes: 43
From: Cheyenne, Wy
Shop said he is changing internal spring(s) for line pressure. Should be done today but I work to 9pm today so will be tomorrow afternoon before I can test it again. Thanks for the help.
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