Home » Public Forums » GMCnet » [GMCnet] No 3rd Gear - another transmission problem
| [GMCnet] No 3rd Gear - another transmission problem [message #286818] |
Mon, 07 September 2015 13:37  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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Senior Member |
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Leaving Half Moon Bay this morning it was clear that the transmission was not shifting out of first. Slip the selector to Super and it shifted as expected. Up in to Drive and it seemed as if it wanted to go into drive, but would not - stayed in 2nd.
A thousand things went through my mind.
I have just replaced the radiator and did not check the transmission fluid - maybe it’s low?
I wonder if I disconnected a vacuum line to the transmission while fooling with the throttle body this morning?
If I have been driving low on fluid could I have burned up the transmission?
Maybe I should wiggle the selector to see if the linkage could be off a little?
We pulled in to a parking lot where I began to check the transmission level. The top of dipstick came all loose and I wasn’t sure at first if I was stuffing it in too far, or just where it was supposed to be. Needless to say checking the level was a guess. Finally I decided the “stopper” should rest agains the little washer and I used that to dip the pan. It showed that I was low - about 2 pints, so I topped it up.
No change. We drove home in 2nd gear.
Before I go back out to the coach to check it again - any words of advice?
I know there is a modulator and a governor. I suspect the modulator has a vacuum tube to it and it’s on the passenger's side. The governor is next to the speedometer cable on the driver’s side.
I can pull the modulator, after running the engine for a moment, to check the fluid. I’ll look for loose vacuum tubes. What else should I look for?
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] No 3rd Gear - another transmission problem [message #286819 is a reply to message #286818] |
Mon, 07 September 2015 13:57  |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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ljdavick wrote on Mon, 07 September 2015 11:37Leaving Half Moon Bay this morning it was clear that the transmission was not shifting out of first. Slip the selector to Super and it shifted as expected. Up in to Drive and it seemed as if it wanted to go into drive, but would not - stayed in 2nd.
A thousand things went through my mind.
I have just replaced the radiator and did not check the transmission fluid - maybe it's low?
I wonder if I disconnected a vacuum line to the transmission while fooling with the throttle body this morning?
If I have been driving low on fluid could I have burned up the transmission?
Maybe I should wiggle the selector to see if the linkage could be off a little?
We pulled in to a parking lot where I began to check the transmission level. The top of dipstick came all loose and I wasn't sure at first if I was stuffing it in too far, or just where it was supposed to be. Needless to say checking the level was a guess. Finally I decided the "stopper" should rest agains the little washer and I used that to dip the pan. It showed that I was low - about 2 pints, so I topped it up.
No change. We drove home in 2nd gear.
Before I go back out to the coach to check it again - any words of advice?
I know there is a modulator and a governor. I suspect the modulator has a vacuum tube to it and it's on the passenger's side. The governor is next to the speedometer cable on the driver's side.
I can pull the modulator, after running the engine for a moment, to check the fluid. I'll look for loose vacuum tubes. What else should I look for?
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
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It is a bad week for transmissions first Fay then gene and now you? Is it a recent rebuild? I would make sure the vacuum to the modulator is ok then check the modulator next I would call Manny.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] No 3rd Gear - another transmission problem [message #286832 is a reply to message #286818] |
Mon, 07 September 2015 17:36 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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ljdavick wrote on Mon, 07 September 2015 11:37Leaving Half Moon Bay this morning it was clear that the transmission was not shifting out of first. Slip the selector to Super and it shifted as expected. Up in to Drive and it seemed as if it wanted to go into drive, but would not - stayed in 2nd.
I can pull the modulator, after running the engine for a moment, to check the fluid. I'll look for loose vacuum tubes. What else should I look for?
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
Larry,
Yes, check the modulator, but don't pull it. Fluid will run out if it is slightly over full or not sitting level. There is a hose between the metal line coming down and the modulator. It has a 90* bend and that is a likely place to crack. Mine cracked just where it plugged into the modulator. I put on a new hose and my symptoms of no 3rd gear went away. THere is also a hose between the metal line and the intake, on top of the engine. That could crack as well. Because this happened suddenly, I would not suspect a plugged steel line.
But... at about 55-57 mine would finally shift to third... because the governor forced the shift. This was my experience.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] No 3rd Gear - another transmission problem [message #286833 is a reply to message #286818] |
Mon, 07 September 2015 17:39 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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ljdavick wrote on Mon, 07 September 2015 11:37Leaving Half Moon Bay this morning it was clear that the transmission was not shifting out of first. Slip the selector to Super and it shifted as expected. Up in to Drive and it seemed as if it wanted to go into drive, but would not - stayed in 2nd.
A thousand things went through my mind.
I can pull the modulator, after running the engine for a moment, to check the fluid. I'll look for loose vacuum tubes. What else should I look for?
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
Larry,
Yes, check the modulator, but don't pull it, yet. Fluid will run out if it is slightly over full or not sitting level. There is a hose between the metal line coming down and the modulator. It has a 90* bend and that is a likely place to crack. Mine cracked just where it plugged into the modulator. I put on a new hose and my symptoms of no 3rd gear went away. THere is also a hose between the metal line and the intake, on top of the engine. That could crack as well. Because this happened suddenly, I would not suspect a plugged steel line.
But... at about 55-57 mine would finally shift to third... because the governor forced the shift. This was my experience.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] No 3rd Gear - another transmission problem [message #286911 is a reply to message #286833] |
Wed, 09 September 2015 03:07 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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You have the symptom of no vacuum to the modulator. As previously stated this could be a cracked or disconnected hose. When mine did this, one day it worked correctly and the next day day it did not work at all. I started diagnosing it by taking a long piece of hose and attached it to the hose at the modulator with a "tee". I ran the hose in the passenger side window and attached a vacuum gage to it. Now I could observe the vacuum level while driving. I had a slight amount of vacuum available but no where near what I could read at the manifold
All of the hoses were good and it turned out to be a blockage in the steel tubing that runs across the manifold from front to rear. I took the tube off and could not blow a reasonable quantity of air through it. I tried to clean it out with a wire but got nowhere. I finally attached shop air to the tube (100 PSI) and gently heated the area of the blockage with acetylene. That cleared the blockage. Then I repainted and reinstalled the tube. I have never had a problem with it since then.
When Dan Gregg had a similar problem I told him it had to the same as mine. I was wrong. He had a governor problem that Wally eventually fixed. So check the vacuum level at the modulator. If necessary do it while driving. If it is good, then go chase the governor.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] No 3rd Gear - another transmission problem [message #286923 is a reply to message #286922] |
Wed, 09 September 2015 08:23 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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Yes, Rob. The metal tube does have a small crimp or restriction in it. This was there to slow down the vacuum or perhaps the release of vacuum so that the modulator did not change position too quickly.
I guess you could call this a dampening effect.
Emery Stora
77 Kingsley
Frederick, CO
Emery
> On Sep 9, 2015, at 7:16 AM, Robert Mueller wrote:
>
> Ken,
>
> I vaguely remember someone (I think it was Bill Bramlet) mentioning that line has a restrictor in it and he drills them out.
>
> I could be wrong about any part of the above statement and possibly all of it! The operative word is VAGUELY!
>
> Regards,
> Rob M.
> The Pedantic Mechanic
>
> -----Original Message-----
> From: Ken Burton
>
> You have the symptom of no vacuum to the modulator. As previously stated this could be a cracked or disconnected hose. When mine
> did this, one day it worked correctly and the next day day it did not work at all. I started diagnosing it by taking a long piece
> of hose and attached it to the hose at the modulator with a "tee". I ran the hose in the passenger side window and attached a
> vacuum gage to it. Now I could observe the vacuum level while driving. I had a slight amount of vacuum available but no where near
> what I could read at the manifold
>
> All of the hoses were good and it turned out to be a blockage in the steel tubing that runs across the manifold from front to rear.
> I took the tube off and could not blow a reasonable quantity of air through it. I tried to clean it out with a wire but got
> nowhere. I finally attached shop air to the tube (100 PSI) and gently heated the area of the blockage with acetylene. That cleared
> the blockage. Then I repainted and reinstalled the tube. I have never had a problem with it since then.
>
> When Dan Gregg had a similar problem I told him it had to the same as mine. I was wrong. He had a governor problem that Wally
> eventually fixed. So check the vacuum level at the modulator. If necessary do it while driving. If it is good, then go chase the
> governor.
> --
> Ken
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] No 3rd Gear - another transmission problem [message #286963 is a reply to message #286922] |
Wed, 09 September 2015 16:36 |
Bruce Hart
Messages: 1501
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
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Senior Member |
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Rob,
You are correct that Bill B. removes the restriction by cutting it off. He
did mine a couple of years ago.
On Wed, Sep 9, 2015 at 7:16 AM, Robert Mueller
wrote:
> Ken,
>
> I vaguely remember someone (I think it was Bill Bramlet) mentioning that
> line has a restrictor in it and he drills them out.
>
> I could be wrong about any part of the above statement and possibly all of
> it! The operative word is VAGUELY!
>
> Regards,
> Rob M.
> The Pedantic Mechanic
>
> -----Original Message-----
> From: Ken Burton
>
> You have the symptom of no vacuum to the modulator. As previously stated
> this could be a cracked or disconnected hose. When mine
> did this, one day it worked correctly and the next day day it did not work
> at all. I started diagnosing it by taking a long piece
> of hose and attached it to the hose at the modulator with a "tee". I ran
> the hose in the passenger side window and attached a
> vacuum gage to it. Now I could observe the vacuum level while driving. I
> had a slight amount of vacuum available but no where near
> what I could read at the manifold
>
> All of the hoses were good and it turned out to be a blockage in the steel
> tubing that runs across the manifold from front to rear.
> I took the tube off and could not blow a reasonable quantity of air
> through it. I tried to clean it out with a wire but got
> nowhere. I finally attached shop air to the tube (100 PSI) and gently
> heated the area of the blockage with acetylene. That cleared
> the blockage. Then I repainted and reinstalled the tube. I have never
> had a problem with it since then.
>
> When Dan Gregg had a similar problem I told him it had to the same as
> mine. I was wrong. He had a governor problem that Wally
> eventually fixed. So check the vacuum level at the modulator. If
> necessary do it while driving. If it is good, then go chase the
> governor.
> --
> Ken
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
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Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: [GMCnet] No 3rd Gear - another transmission problem [message #286995 is a reply to message #286922] |
Thu, 10 September 2015 00:57 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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USAussie wrote on Wed, 09 September 2015 08:16Ken,
I vaguely remember someone (I think it was Bill Bramlet) mentioning that line has a restrictor in it and he drills them out.
I could be wrong about any part of the above statement and possibly all of it! The operative word is VAGUELY!
Regards,
Rob M.
The Pedantic Mechanic
I intensionally did not mention the restrictor. The restrictor is the area on mine that was plugged with carbon and I heated to remove the carbon blockage. It is located on the front of the pipe nearest the carburetor and is just a crimp about 1" or 2" from the end. I figured it was there for a reason so I did not cut it off.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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