odd shift - The 1947 - Present Chevrolet & GMC Truck Message Board Network

79gmcc15 · 02-15-2005, 06:53 AM

ever since I put on my crappy q-jet (got taken for a ride) my trans has been down shifting weird.. Ive noticed that it shifts from 3rd alright but when I am stopping it seems to go from 2nd to 1st then shift again. so it seems like it shifts 4 times. did I some how install the tranny cable wrong? (th350) and one last thing can a q-jet make the motor diesel after shuting it down? its been doing that almost every day, esp. after a semi long trip. Its so much fun when you shut it off and it runs on for about 2 sec. and then gray smoke comes out of the carb

thank you all.

TrainD5115 · 02-15-2005, 10:39 AM

It will "diesel" if its idleing too high when its shut off. Mine will do it once in awhile if I can't kick the idle down to a reasonable level. I have been struggling with an idle problem for sometime now. I'm wondering if it might be a bad power valve because my fuel mileage is really suffering. I don't know what to tell you about the tranny shifting. I can feel mine downshifting more now with the idle problem but it still operates properly. Check out this vacuum nightmare!

79gmcc15 · 02-15-2005, 12:51 PM

haha kinda looks like mine, I have what seems to be WAY to many hoeses... my carb has been idleing realy high around a 1000 *guess no tach* but then again I dont have the electric choke hooked up. dont have a wire to wrap around the prong and dont know exactly where to hook it up too.. and diagrams are like germen to me, never makes sence.I am more of a show me or picture guy.. now that I think about it it does seem to shift odd when the revs are higher then they should be.. I should try to pay a closer look at it.

79gmcc15 · 02-15-2005, 12:55 PM

btw do you use your cruse controle? I think some PO's dissconnected it some time ago. and just rencently found out that, thats what that big black disk with the rod connected to the carb was for.. always wondered what the button on the turn signal was for lol. p.s. we seem to have simular componets. I have 3.73 rear end and a 350/350... what is your normal city GPM if you remember? because I am geting around 7 GPM

TrainD5115 · 02-17-2005, 11:15 AM

I have cruise but it slips and surges so I don't use it. I am getting around 11-12 mpg right now. Probably a little less in town. I drive 34 miles round trip to work everyday 6 city/ 28 hwy so most of the trip is done at 60mph. I burn oil at anything over 65mph. I had another member tell me that my butterflies were off their seats awhile back but I still think I have an undiscovered vacuum leak because of the way my idle is way up after it warms up. Everything I've heard is that a vacuum leak will cause it to suck extra fuel.

cobb_ben · 02-17-2005, 11:33 AM

Do you have the vaccume modulator hooked up proberly to vaccume form the carb??? It needs to be hooked up to non-ported vaccume, aka vaccume all of the time, this is what controls the shifting of the tranny, my TH-350 doesnt have a tranny cable. Thats just my $.02.

02-15-2005, 06:53 AM	#1
79gmcc15 Gettin It One Pice At A Time Join Date: Oct 2004 Location: everett, washington Posts: 2,688	odd shift ever since I put on my crappy q-jet (got taken for a ride) my trans has been down shifting weird.. Ive noticed that it shifts from 3rd alright but when I am stopping it seems to go from 2nd to 1st then shift again. so it seems like it shifts 4 times. did I some how install the tranny cable wrong? (th350) and one last thing can a q-jet make the motor diesel after shuting it down? its been doing that almost every day, esp. after a semi long trip. Its so much fun when you shut it off and it runs on for about 2 sec. and then gray smoke comes out of the carb thank you all. __________________ RIP ELJAY Work In Progress 1979 GMC C1500 Trailering Special. Getting the truck done, one piece at a time. “You can tell a lot about a fellow’s character by his way of eating jellybeans.”Ronald Reagan “I don’t know the key to success but I know the key to failure is trying to please everybody.” Bill Cosby

02-15-2005, 10:39 AM	#2
TrainD5115 North Coast, baby! Join Date: Jun 2004 Location: Toledo, OH Posts: 437	It will "diesel" if its idleing too high when its shut off. Mine will do it once in awhile if I can't kick the idle down to a reasonable level. I have been struggling with an idle problem for sometime now. I'm wondering if it might be a bad power valve because my fuel mileage is really suffering. I don't know what to tell you about the tranny shifting. I can feel mine downshifting more now with the idle problem but it still operates properly. Check out this vacuum nightmare! __________________ Brad 79 Scottsdale C20 350/350 3.73's Still running full CA smog gear!

02-15-2005, 12:51 PM	#3
79gmcc15 Gettin It One Pice At A Time Join Date: Oct 2004 Location: everett, washington Posts: 2,688	haha kinda looks like mine, I have what seems to be WAY to many hoeses... my carb has been idleing realy high around a 1000 guess no tach but then again I dont have the electric choke hooked up. dont have a wire to wrap around the prong and dont know exactly where to hook it up too.. and diagrams are like germen to me, never makes sence.I am more of a show me or picture guy.. now that I think about it it does seem to shift odd when the revs are higher then they should be.. I should try to pay a closer look at it. __________________ RIP ELJAY Work In Progress 1979 GMC C1500 Trailering Special. Getting the truck done, one piece at a time. “You can tell a lot about a fellow’s character by his way of eating jellybeans.”Ronald Reagan “I don’t know the key to success but I know the key to failure is trying to please everybody.” Bill Cosby

02-15-2005, 12:55 PM	#4
79gmcc15 Gettin It One Pice At A Time Join Date: Oct 2004 Location: everett, washington Posts: 2,688	btw do you use your cruse controle? I think some PO's dissconnected it some time ago. and just rencently found out that, thats what that big black disk with the rod connected to the carb was for.. always wondered what the button on the turn signal was for lol. p.s. we seem to have simular componets. I have 3.73 rear end and a 350/350... what is your normal city GPM if you remember? because I am geting around 7 GPM __________________ RIP ELJAY Work In Progress 1979 GMC C1500 Trailering Special. Getting the truck done, one piece at a time. “You can tell a lot about a fellow’s character by his way of eating jellybeans.”Ronald Reagan “I don’t know the key to success but I know the key to failure is trying to please everybody.” Bill Cosby Last edited by 79gmcc15; 02-15-2005 at 12:58 PM.

02-17-2005, 11:15 AM	#5
TrainD5115 North Coast, baby! Join Date: Jun 2004 Location: Toledo, OH Posts: 437	I have cruise but it slips and surges so I don't use it. I am getting around 11-12 mpg right now. Probably a little less in town. I drive 34 miles round trip to work everyday 6 city/ 28 hwy so most of the trip is done at 60mph. I burn oil at anything over 65mph. I had another member tell me that my butterflies were off their seats awhile back but I still think I have an undiscovered vacuum leak because of the way my idle is way up after it warms up. Everything I've heard is that a vacuum leak will cause it to suck extra fuel. __________________ Brad 79 Scottsdale C20 350/350 3.73's Still running full CA smog gear!

02-17-2005, 11:33 AM	#6
cobb_ben Registered User Join Date: Feb 2004 Location: Fort Leonard Wood Mo Posts: 299	Do you have the vaccume modulator hooked up proberly to vaccume form the carb??? It needs to be hooked up to non-ported vaccume, aka vaccume all of the time, this is what controls the shifting of the tranny, my TH-350 doesnt have a tranny cable. Thats just my $.02.



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