Speedo Question
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Senior User
Joined: Aug 2008
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From: FL's Ghettos/Trailer Prk
Speedo Question
I'm new to forums and conducted a search for this, but could not find it. I might not being doing it right though. So here it goes. I was having tranny issues so I changed the modulator and replaced the filter. It works fine except now have a hard shift and won't **** to 2nd until 3K think it is the VRV. But now my speedometer runs backwards in reverse, didn't do it before. Any suggestions on the cause and the fix. Any help is welcomed and appreciated thak you.
Tuned
Joined: Oct 2004
Posts: 250
Likes: 6
From: new york
I'm guessing you have a vacuum controlled C-6 transmission. If that is the case, if you disconnect and plug the vacuum supply at the injection pumpand I think that also has a kick down rod, that my have been bent, you need to disconnect it at the trany it is located just above the shifting linkage on the trany. Then drive the truck it should shift quickly to third. If not you still have trany issues.
The speedo issue would not be related to the trany unless you have an E40d
The speedo issue would not be related to the trany unless you have an E40d
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Senior User
Joined: Aug 2008
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From: FL's Ghettos/Trailer Prk
Sorry about that , it's a 1988 f250 7.3 4X4 C6 tranny. I didn't think it had anything to do with the tranny, but it seemed odd it started right after I changed the filter and modulator. Pulled into the barn it was working, changed the parts, pulled out and it's going backwards.
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
Lead_Pusher,
Welcome to FTE and the IDI forum.
Are you sure it did not go backwards?
I have an 86, when I plow snow at the mall I drive in reverse a lot.
Something like 1/2 mile forwards, 1/2 mile in reverse, one mile traveled and the odometer is back to the same place it was before I started.
As for the late shifts, sounds like the VRV on the IP that controls the transmission needs adjusted.
Welcome to FTE and the IDI forum.
Are you sure it did not go backwards?
I have an 86, when I plow snow at the mall I drive in reverse a lot.
Something like 1/2 mile forwards, 1/2 mile in reverse, one mile traveled and the odometer is back to the same place it was before I started.
As for the late shifts, sounds like the VRV on the IP that controls the transmission needs adjusted.
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Senior User
Joined: Aug 2008
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From: FL's Ghettos/Trailer Prk
Thanks for the help. I'm sure I've never noticed it before
. I think it just happened because now the speedo sits at the bottom of the gauge below the zero mark. I'm planning on getting a gauge and checkig the VRV. On the plus side I could mark the bottom of the gauge and know how fast I'm going backwards 
. I think it just happened because now the speedo sits at the bottom of the gauge below the zero mark. I'm planning on getting a gauge and checkig the VRV. On the plus side I could mark the bottom of the gauge and know how fast I'm going backwards
Post Fiend
Joined: Nov 2003
Posts: 21,285
Likes: 15
From: Nutter Fort, WV
My speedometer has a peg at zero that will not let it go below zero, but the odometer does run backwards when in reverse.
I noticed mine did that when I plowed for 12 hours straight, burnt a 1/2 tank of fuel, and according to the odometer, I only drove 20 miles.
15 of that was from the house to the mall and back, so that amounted to five miles in 12 hours of driving.
Normal plow RPM is about 1800 - 2000, which is 12.3 - 13.7 MPH in low gear or reverse.
That also really messes with my average MPG for the year, I just show a bit over 12 MPG for this year as of the last tank full.
I noticed mine did that when I plowed for 12 hours straight, burnt a 1/2 tank of fuel, and according to the odometer, I only drove 20 miles.
15 of that was from the house to the mall and back, so that amounted to five miles in 12 hours of driving.
Normal plow RPM is about 1800 - 2000, which is 12.3 - 13.7 MPH in low gear or reverse.
That also really messes with my average MPG for the year, I just show a bit over 12 MPG for this year as of the last tank full.
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From: FL's Ghettos/Trailer Prk
Talked to a fleet mechanic at work, not a diesel mech., but gassers have speedos too. He says my speedo is shot, does anyone know how to test them?
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