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Old 08-26-2019, 12:45 AM   #1
stomper
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T350 hard 1-2 upshift

I have an unknown 3spd automatic in an 81 C10 i just bought. Assuming it's a turbo 350 but the truck was converted from a 3 on the tree. It's a nice conversion you couldn't tell from factory sitting in the cab. It shifts hard on the 1-2 upshift. 2-3 is like butter. Otherwise the trans works great. When I got it the throttle position cable was disconnected so i thought it was that. Nope. Hooked it up and no change. Inspected the lines and signal to the vacuum modulator. I have 20+ Hg. I turned the vacuum modulator in which gave me a later shift like its supposed to and the shift was harder. I turned it way out and it got slightly better but not much. I replaced the vacuum modulator and the problem did not change. What causes should I look for? What should I try next?
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'81 C10 Stepside no options
'73 P10 StepVan 4.8l LS / 4l60e shorty
'83 K30 SRW Silverado Factory 454 / T400 / NP205 loaded
'61 Bel Air Bubbletop V8 3rd owner
'08 Z06 Silver 427 LS
Past Notable Rigs
'85 K10 Silverado Red / Charcoal
'86 K20 Suburban 6" lift and 35's
'72 K5 CST Tilt Tach Air. Original paint, Med Bronze / Saddle
'71 C10 Cheyenne Short Box, Hugger Orange Saddle Buckets, 350 / 700r 3.73 posi
'68 C10 Stepper, 250 / 4 spd
'83 K10 W/T Mahogony 305 / 700r posi
'68 Camaro RS 43k mi 327 California car
'78 GMC Short Box Sierra Classic Heavy Hauler 350 / 350 AC Cruise
'67 Biscayne 2dr 396
'83 GMC SWB 6cyl NP440 4spd OD 65k mi CA truck
'86 GMC SWB 350 700r
'99 C5 Roadster Z51 6spd
'79 P10 StepVan Small Block / T350 shorty
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Old 08-26-2019, 07:04 AM   #2
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Re: T350 hard 1-2 upshift

Is it possible someone installed a shift kit? Most disable the 1-2 accumulator which is the shock absorber for the shift.

On the passenger side of the transmission is a cylinder cover about 2" in diameter. A small hole, towards the rear, is to insert a scribe and dislodge the snap ring. After removal of the cover there should be a 3" long spring. Likely it's broken or missing. Unlikely but the piston under the spring is damage.

The Superior HP shift kit disables the accumlator by blocking the passage so the above spring and piston could be in place.
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Old 08-26-2019, 10:21 AM   #3
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Re: T350 hard 1-2 upshift

It's possible but it hits hard at all throttle positions. Something is not right. I'll check the spring. Thanks Bigdav.
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"I was patina when patina wasn't cool."
'81 C10 Stepside no options
'73 P10 StepVan 4.8l LS / 4l60e shorty
'83 K30 SRW Silverado Factory 454 / T400 / NP205 loaded
'61 Bel Air Bubbletop V8 3rd owner
'08 Z06 Silver 427 LS
Past Notable Rigs
'85 K10 Silverado Red / Charcoal
'86 K20 Suburban 6" lift and 35's
'72 K5 CST Tilt Tach Air. Original paint, Med Bronze / Saddle
'71 C10 Cheyenne Short Box, Hugger Orange Saddle Buckets, 350 / 700r 3.73 posi
'68 C10 Stepper, 250 / 4 spd
'83 K10 W/T Mahogony 305 / 700r posi
'68 Camaro RS 43k mi 327 California car
'78 GMC Short Box Sierra Classic Heavy Hauler 350 / 350 AC Cruise
'67 Biscayne 2dr 396
'83 GMC SWB 6cyl NP440 4spd OD 65k mi CA truck
'86 GMC SWB 350 700r
'99 C5 Roadster Z51 6spd
'79 P10 StepVan Small Block / T350 shorty
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Old 08-30-2019, 01:42 PM   #4
GASoline71
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Re: T350 hard 1-2 upshift

Depending on the shift kit, every 1-2 shift can be firm. That's the way mine is set up...

Gary
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Quote:
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Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 08-30-2019, 06:11 PM   #5
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Re: T350 hard 1-2 upshift

At this point, no one knows if it has a shift kit or not, in the original post it refers to hooking up the detent cable which didn't fix it so I am assuming its a T350 from that info.

If the 1-2 accumulator spring is not broken or missing, check the governor. most likely its the 1-2 accumulator spring broken or missing.

GM released two different 1-2 accumulator covers, one steel and one aluminum
When installing the steel cover, need to install the o-ring in the case when you have the steel cover, when you have the aluminum cover the o-ring goes on the cover as you install it. Making sure of course the accumulator piston and the spring goes in before installing either cover. snap ring holds the cover in the bore. Use something like trans jel or stp on the o-ring/cover as you install the cover. If you don't get the o-ring right once that trans shifts into second it will let you know if its not right. clean up in aisle 3 !!!!!
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Old 09-09-2019, 11:31 AM   #6
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Re: T350 hard 1-2 upshift

I bet $10 on a new accumulator spring and o-ring before I take it apart. I will report back.
__________________
"I was patina when patina wasn't cool."
'81 C10 Stepside no options
'73 P10 StepVan 4.8l LS / 4l60e shorty
'83 K30 SRW Silverado Factory 454 / T400 / NP205 loaded
'61 Bel Air Bubbletop V8 3rd owner
'08 Z06 Silver 427 LS
Past Notable Rigs
'85 K10 Silverado Red / Charcoal
'86 K20 Suburban 6" lift and 35's
'72 K5 CST Tilt Tach Air. Original paint, Med Bronze / Saddle
'71 C10 Cheyenne Short Box, Hugger Orange Saddle Buckets, 350 / 700r 3.73 posi
'68 C10 Stepper, 250 / 4 spd
'83 K10 W/T Mahogony 305 / 700r posi
'68 Camaro RS 43k mi 327 California car
'78 GMC Short Box Sierra Classic Heavy Hauler 350 / 350 AC Cruise
'67 Biscayne 2dr 396
'83 GMC SWB 6cyl NP440 4spd OD 65k mi CA truck
'86 GMC SWB 350 700r
'99 C5 Roadster Z51 6spd
'79 P10 StepVan Small Block / T350 shorty
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Old 09-12-2019, 12:28 AM   #7
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Re: T350 hard 1-2 upshift

I took out the short spring and installed the long orange spring. It's slightly better if I barely press the gas. If I accelerate fast enough to keep up with traffic, the shift rattles the change in the ashtray. Ideas?
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"I was patina when patina wasn't cool."
'81 C10 Stepside no options
'73 P10 StepVan 4.8l LS / 4l60e shorty
'83 K30 SRW Silverado Factory 454 / T400 / NP205 loaded
'61 Bel Air Bubbletop V8 3rd owner
'08 Z06 Silver 427 LS
Past Notable Rigs
'85 K10 Silverado Red / Charcoal
'86 K20 Suburban 6" lift and 35's
'72 K5 CST Tilt Tach Air. Original paint, Med Bronze / Saddle
'71 C10 Cheyenne Short Box, Hugger Orange Saddle Buckets, 350 / 700r 3.73 posi
'68 C10 Stepper, 250 / 4 spd
'83 K10 W/T Mahogony 305 / 700r posi
'68 Camaro RS 43k mi 327 California car
'78 GMC Short Box Sierra Classic Heavy Hauler 350 / 350 AC Cruise
'67 Biscayne 2dr 396
'83 GMC SWB 6cyl NP440 4spd OD 65k mi CA truck
'86 GMC SWB 350 700r
'99 C5 Roadster Z51 6spd
'79 P10 StepVan Small Block / T350 shorty
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Old 09-12-2019, 07:21 AM   #8
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Re: T350 hard 1-2 upshift

Somebody must have put a shift kit in it.
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Old 09-12-2019, 09:57 AM   #9
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Re: T350 hard 1-2 upshift

OK so what changes does a 'shift kit' make to a T350 to cause the hard 1-2 upshift and how can I 'un shift kit' this thing?
__________________
"I was patina when patina wasn't cool."
'81 C10 Stepside no options
'73 P10 StepVan 4.8l LS / 4l60e shorty
'83 K30 SRW Silverado Factory 454 / T400 / NP205 loaded
'61 Bel Air Bubbletop V8 3rd owner
'08 Z06 Silver 427 LS
Past Notable Rigs
'85 K10 Silverado Red / Charcoal
'86 K20 Suburban 6" lift and 35's
'72 K5 CST Tilt Tach Air. Original paint, Med Bronze / Saddle
'71 C10 Cheyenne Short Box, Hugger Orange Saddle Buckets, 350 / 700r 3.73 posi
'68 C10 Stepper, 250 / 4 spd
'83 K10 W/T Mahogony 305 / 700r posi
'68 Camaro RS 43k mi 327 California car
'78 GMC Short Box Sierra Classic Heavy Hauler 350 / 350 AC Cruise
'67 Biscayne 2dr 396
'83 GMC SWB 6cyl NP440 4spd OD 65k mi CA truck
'86 GMC SWB 350 700r
'99 C5 Roadster Z51 6spd
'79 P10 StepVan Small Block / T350 shorty
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Old 09-12-2019, 01:01 PM   #10
GASoline71
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Re: T350 hard 1-2 upshift

There are 4 small check balls in the passages in the valve body. Most shift kits have you remove a few or all of them. The check balls provide a restriction to the oil feeds/pressure and allow for smoother shifts. With them removed you get full pressure and firmer shifts. You'd have to pull the valve body and confirm they are missing and then source new ones to put in the original locations.

Gary
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My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

The Rebuild of Creeping Death after the wreck

Quote:
Originally Posted by LONGHAIR View Post
I would never rebuild a 305.
Quote:
Originally Posted by prostreetC-10 View Post
I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
Quote:
Originally Posted by Marv D View Post
Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 09-12-2019, 05:00 PM   #11
YoungPup1977
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Re: T350 hard 1-2 upshift

Maybe check the easy stuff first. Check the governor, I mentioned this in previous post....
before you start taking the VB off.

When checking the governor, check the springs. They make different combinations of springs and you do not have to take the governor a part to change these springs. Very simple process to change out the springs.

Last edited by YoungPup1977; 09-12-2019 at 05:19 PM.
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Old 09-12-2019, 05:05 PM   #12
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Re: T350 hard 1-2 upshift

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Originally Posted by YoungPup1977 View Post
Maybe check the easy stuff first. Check the governor, I mentioned this is previous post....
before you start taking the VB off.
As far as I know the governor only controls the shift points which seem fine, not the firmness of the shift.
__________________
"I was patina when patina wasn't cool."
'81 C10 Stepside no options
'73 P10 StepVan 4.8l LS / 4l60e shorty
'83 K30 SRW Silverado Factory 454 / T400 / NP205 loaded
'61 Bel Air Bubbletop V8 3rd owner
'08 Z06 Silver 427 LS
Past Notable Rigs
'85 K10 Silverado Red / Charcoal
'86 K20 Suburban 6" lift and 35's
'72 K5 CST Tilt Tach Air. Original paint, Med Bronze / Saddle
'71 C10 Cheyenne Short Box, Hugger Orange Saddle Buckets, 350 / 700r 3.73 posi
'68 C10 Stepper, 250 / 4 spd
'83 K10 W/T Mahogony 305 / 700r posi
'68 Camaro RS 43k mi 327 California car
'78 GMC Short Box Sierra Classic Heavy Hauler 350 / 350 AC Cruise
'67 Biscayne 2dr 396
'83 GMC SWB 6cyl NP440 4spd OD 65k mi CA truck
'86 GMC SWB 350 700r
'99 C5 Roadster Z51 6spd
'79 P10 StepVan Small Block / T350 shorty
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Old 09-12-2019, 05:45 PM   #13
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Re: T350 hard 1-2 upshift

LOL!!!! OK ! From your first post you were assuming its a T350 which you didn't know what trans you had, now you are a expert on how the governor works...LOL!!! This forum makes me laugh my ass off...

How hard would it be to remove the governor before you drop the pan and the VB on your back ? But do what you think, its your problem.

Once you drop the VB what are you looking for, check balls ? What about the separator plate ? 2nd gear feed in the plate ?

If you turn the screw in the modulator does it change the shift points ? later shifts/early shifts ? Thought the governor did this ? LOL!!!!

Free Advice is hard to get, whats even harder is the right advice !!

GOOD LUCK TO YOU !!
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Old 09-12-2019, 05:47 PM   #14
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Re: T350 hard 1-2 upshift

I have a TCI th350 in my truck and it is suppose to have firm shifts. It also has heavy duty clutches and other internals. Maybe you have something simular in your truck.
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Old 09-12-2019, 06:03 PM   #15
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Re: T350 hard 1-2 upshift

Quote:
Originally Posted by YoungPup1977 View Post
LOL!!!! OK ! From your first post you were assuming its a T350 which you didn't know what trans you had, now you are a expert on how the governor works...LOL!!! This forum makes me laugh my ass off...

How hard would it be to remove the governor before you drop the pan and the VB on your back ? But do what you think, its your problem.

Once you drop the VB what are you looking for, check balls ? What about the separator plate ? 2nd gear feed in the plate ?

If you turn the screw in the modulator does it change the shift points ? later shifts/early shifts ? Thought the governor did this ? LOL!!!!

GOOD LUCK TO YOU !!
Alright 'youngpup' I didn't bother to look under the truck to see if it was a T350 or T400. I know what I'm looking at. I can take the air cleaner lid off and look at the carb throat easily too but I doubt that is going to change the shift firmness either. This has been the most respectful and helpful forum I have been a member of for 17 years. Probably since before you were sucking on your mama's tit. Never have I had such a jack-off comment as yours.
__________________
"I was patina when patina wasn't cool."
'81 C10 Stepside no options
'73 P10 StepVan 4.8l LS / 4l60e shorty
'83 K30 SRW Silverado Factory 454 / T400 / NP205 loaded
'61 Bel Air Bubbletop V8 3rd owner
'08 Z06 Silver 427 LS
Past Notable Rigs
'85 K10 Silverado Red / Charcoal
'86 K20 Suburban 6" lift and 35's
'72 K5 CST Tilt Tach Air. Original paint, Med Bronze / Saddle
'71 C10 Cheyenne Short Box, Hugger Orange Saddle Buckets, 350 / 700r 3.73 posi
'68 C10 Stepper, 250 / 4 spd
'83 K10 W/T Mahogony 305 / 700r posi
'68 Camaro RS 43k mi 327 California car
'78 GMC Short Box Sierra Classic Heavy Hauler 350 / 350 AC Cruise
'67 Biscayne 2dr 396
'83 GMC SWB 6cyl NP440 4spd OD 65k mi CA truck
'86 GMC SWB 350 700r
'99 C5 Roadster Z51 6spd
'79 P10 StepVan Small Block / T350 shorty

Last edited by stomper; 09-12-2019 at 06:18 PM.
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Old 09-12-2019, 06:14 PM   #16
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Re: T350 hard 1-2 upshift

.
.
<----




"Alright 'youngpup' I didn't bother to look under the truck to see if it was a T350 or T400. I know what I'm looking at. I can take the air cleaner lid off and look at the carb throat easily too but I doubt that is going to change the shift firmness either. This has been the most respectful and helpful forum I have been a member of for 17 years. Probably since before you were sucking on your mama's tit. Never have I had such a jack-off comment as yours."



Sounds like you don't even know where the governor is even located....why would you look at the carb throat ? LOL!!! My Mother has nothing to do with this !! She is no longer here so lets talk about respect, I was only trying to help you...but I can see how this forum is and who attends.

Last edited by YoungPup1977; 09-12-2019 at 09:25 PM.
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Old 09-13-2019, 10:41 AM   #17
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Re: T350 hard 1-2 upshift

I get its a full moon, but seriously? What part of no pissing matches is hard to understand?

III. No pissing matches. Its fine to disagree, but once a thread has run its course, and degenerated into little more than an insult fest, it will be locked. While this will require a judgment call by the Administrators & Moderators. The members of this site can keep our moderating to a minimum by exercising a little discretion and self- control. Excessive profanity will lead to a 24 hour suspension at the Administrations discretion.

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Old 09-13-2019, 10:44 AM   #18
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Re: T350 hard 1-2 upshift

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Originally Posted by YoungPup1977 View Post
.
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<----
.
I will edit your profile for you. Causing discontent is not what this community is about. Try using the report a post feature in the future should you chose to come back.

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XIII. If you are a long time member, act like one. Lead by example and assist other newer members rather then attacking them. We look upon our veteran members to use this opportunity to teach the newer members the appropriate message board usage.
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Old 09-13-2019, 10:47 AM   #19
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Re: T350 hard 1-2 upshift

Quote:
Originally Posted by stomper View Post
Alright 'youngpup' I didn't bother to look under the truck to see if it was a T350 or T400. I know what I'm looking at. I can take the air cleaner lid off and look at the carb throat easily too but I doubt that is going to change the shift firmness either. This has been the most respectful and helpful forum I have been a member of for 17 years. Probably since before you were sucking on your mama's tit. Never have I had such a jack-off comment as yours.
And this was no better.. Again review the site rules
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