transmission question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

no1uno55 · 01-08-2009, 09:01 PM

i bought a 84 swb last year and is my daily driver now.(started life with a 305 th350) in sept.2000 original owner had a new gm crate 350 installed same transmisson. the engine only have 20000 miles on it but it shifts to early. is there a adj. somewhere or a cable or something.what i mean by early is after i take off the first few gears are fine but it will shift into high gear way to early but if i give it a little more gas it will shift back. when its cold it dont do it or when i pull a trailer. the original owner said it has done that since it was new in 1984 and the dealer told him it is the kind of torque coverter it has in it.

also the engine wont rev up real free any ideas?

8 year old 20000 miles on engine, th350, a/c, power stearing, fan, alt., you get the idea. header, duals no cats no cross over pipe turbo muffers (for now)
2 1/4 i think.i have tuned the engine plugs, wires, cap, checked the timing had the carb. cleaned and rebuild. quad-jet. if i just stomp it from a stop it sounds like it is firing to late or something.

thanks in advaced
joe

piecesparts · 01-08-2009, 09:27 PM

Let's cover some basics and see what you really have.
#1 Is the tranny a 350C model? (That is a 350 tranny with a lockup converter SOUNDS like it may be by the POs statement) This will be noted by the 4-pronged plug on the driver's side of the tranny JUST ABOVE the oil pan. If there is no plug, then it is a standard TH350.
#2, do you know what your transmission's "Kick down" cable is adjusted like? If it is adjusted to short at the carb connection, (right below the throttle cable connection on the carb llinkage) then the shift will be early--possible part of your problem. Look at the cable up by the carb and see the black plastic housing that is mounted on the mounting bracket on top of the intake manifold, there is a half-mooned shaped plunger in that housing that you can push into itself (it pushes hard, so try until you figure it out) and push the knurled slide all the way back into the housing. Once you have done that---take the throttle on the carb to full open (without the engine running), the slide should position itself to set up your kick down shift properly.
#3 There is a possibility that you governor is not working properly, inside the tranny. This would require someone with experience to look at this.

#4 You said that you tuned it and set everything. What is the timing set at? What are the plug gaps set at? If it is too low, then the response that you are feeling coud be from that. I would look at setting the timing a little higher than the factory specs and see what happens there. I used to run my 84 at 12 degrees BTDC. Listen for pinging or detonation as you advance timing. What are you running for plug wires? If they are not good, then your ignition voltage could be low and poorly transmitted to the plugs.

#5 You will get a better driving response with a cross-over pipe on the exhaust and upgrading to a set of 2 1/2" pipes

James McClure · 01-09-2009, 12:10 PM

Don't forget the shift modulator. THM350\C Vac can on left rear of trans. Make sure of good vacuum supply and no oil leaks. Most common failure of these is a broken diaphram which will cause a smoke screen out the exhaust. If vehicle shifts at all chances are governor is probably OK. Governor and shift modulator work togther to make shifts up or down. Detent cable is for "forced" downshift IE passing gear within limitation set by governor, EG, trans will not downshift 3rd to 1st above 45 mph, will only shift 3rd to 2nd. It's all a balancing act, and if one thing is out of balance it won't work right. Tcc is an issue all to itself. Eng has got to be running properly for the trans to work properly.jim

no1uno55 · 01-14-2009, 10:54 PM

ok the transmission is a lock up style 350. was told thats just the way they are and the only way to fix it (not that its broken, it just sound like crap when it shift to high gear under normal take off) is to change out the trans and torque converter. does this sound right?

the engine problem. found out the man that cleaned the carb did just that. cleaned and put it back together(not rebuild). i have found a reman Qjet from a man in tulsa ok that i was told is the man on Qjets. i can get one for 150.00 what do yall think?

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01-08-2009, 09:01 PM	#1
no1uno55 Registered User Join Date: Mar 2008 Location: Southaven MS Posts: 25	transmission question i bought a 84 swb last year and is my daily driver now.(started life with a 305 th350) in sept.2000 original owner had a new gm crate 350 installed same transmisson. the engine only have 20000 miles on it but it shifts to early. is there a adj. somewhere or a cable or something.what i mean by early is after i take off the first few gears are fine but it will shift into high gear way to early but if i give it a little more gas it will shift back. when its cold it dont do it or when i pull a trailer. the original owner said it has done that since it was new in 1984 and the dealer told him it is the kind of torque coverter it has in it. also the engine wont rev up real free any ideas? 8 year old 20000 miles on engine, th350, a/c, power stearing, fan, alt., you get the idea. header, duals no cats no cross over pipe turbo muffers (for now) 2 1/4 i think.i have tuned the engine plugs, wires, cap, checked the timing had the carb. cleaned and rebuild. quad-jet. if i just stomp it from a stop it sounds like it is firing to late or something. thanks in advaced joe

01-08-2009, 09:27 PM	#2
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: transmission question Let's cover some basics and see what you really have. #1 Is the tranny a 350C model? (That is a 350 tranny with a lockup converter SOUNDS like it may be by the POs statement) This will be noted by the 4-pronged plug on the driver's side of the tranny JUST ABOVE the oil pan. If there is no plug, then it is a standard TH350. #2, do you know what your transmission's "Kick down" cable is adjusted like? If it is adjusted to short at the carb connection, (right below the throttle cable connection on the carb llinkage) then the shift will be early--possible part of your problem. Look at the cable up by the carb and see the black plastic housing that is mounted on the mounting bracket on top of the intake manifold, there is a half-mooned shaped plunger in that housing that you can push into itself (it pushes hard, so try until you figure it out) and push the knurled slide all the way back into the housing. Once you have done that---take the throttle on the carb to full open (without the engine running), the slide should position itself to set up your kick down shift properly. #3 There is a possibility that you governor is not working properly, inside the tranny. This would require someone with experience to look at this. #4 You said that you tuned it and set everything. What is the timing set at? What are the plug gaps set at? If it is too low, then the response that you are feeling coud be from that. I would look at setting the timing a little higher than the factory specs and see what happens there. I used to run my 84 at 12 degrees BTDC. Listen for pinging or detonation as you advance timing. What are you running for plug wires? If they are not good, then your ignition voltage could be low and poorly transmitted to the plugs. #5 You will get a better driving response with a cross-over pipe on the exhaust and upgrading to a set of 2 1/2" pipes

01-09-2009, 12:10 PM	#3
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: transmission question Don't forget the shift modulator. THM350\C Vac can on left rear of trans. Make sure of good vacuum supply and no oil leaks. Most common failure of these is a broken diaphram which will cause a smoke screen out the exhaust. If vehicle shifts at all chances are governor is probably OK. Governor and shift modulator work togther to make shifts up or down. Detent cable is for "forced" downshift IE passing gear within limitation set by governor, EG, trans will not downshift 3rd to 1st above 45 mph, will only shift 3rd to 2nd. It's all a balancing act, and if one thing is out of balance it won't work right. Tcc is an issue all to itself. Eng has got to be running properly for the trans to work properly.jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.

01-14-2009, 10:54 PM	#4
no1uno55 Registered User Join Date: Mar 2008 Location: Southaven MS Posts: 25	Re: transmission question ok the transmission is a lock up style 350. was told thats just the way they are and the only way to fix it (not that its broken, it just sound like crap when it shift to high gear under normal take off) is to change out the trans and torque converter. does this sound right? the engine problem. found out the man that cleaned the carb did just that. cleaned and put it back together(not rebuild). i have found a reman Qjet from a man in tulsa ok that i was told is the man on Qjets. i can get one for 150.00 what do yall think?



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