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Old 09-29-2018, 02:38 PM   #1
Texasz71
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Th350 question

First post. Long time lurker, first time poster.

So I recently bought my first square body.

1975 k10. 400/350/203

Previous owner said it needed some TLC, and I was ready for a mediocre project.

So right off the bat, the th350 wouldnt shift from 1-2. It had 1 and reverse. So after googling, I replaced the vacuum modulator. It has vacuum at idle. Still no shifty. Next I pulled the governor. Turns out, the plastic gear had broken off. Got it out (nightmare), then put a new plastic gear on. The piston was moving freely. Still no shifty. So I noticed the trans pan was dented and had a slow leak. So I just got finished swapping the pan (one with a drain plug), and added fluid. Fluid level is perfect. Still doesnt shift.

After hours and hours of googlin, I come to yall for other suggestions.

Thanks in advance

Last edited by Texasz71; 09-29-2018 at 02:57 PM.
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Old 09-29-2018, 05:49 PM   #2
Texasz71
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Re: Th350 question

Also, high on the transfer case doesnt work.
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Old 09-30-2018, 12:00 AM   #3
Chevyrestorerman
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Re: Th350 question

How did you get the governor out ? you say nightmare, what exactly made it a nightmare, did you check the surface on the governor where is contacts on to the case....with the gear problem may have caused the governor to wear into the case, sometimes you have to bore the governor hole out and insert a bushing because the governor wore into the case..... Just a thought, no way for me to see the problem, take pics of the governor so we can see.....
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Old 09-30-2018, 01:01 PM   #4
Texasz71
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Re: Th350 question

When I got it out the first time, I just yanked it out.

The problem was getting the plastic gear out. I drilled a hole in it, then threaded a 4 inch deck screw in it, then slowly spun it out. Took me awhile on how to figure that out.

Just pulled the governor out again, it looks like your standard governor. See pic.

Piston still moves freely. Sprayed it down with PB blaster just in case. Going to throw it back in later.

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Old 09-30-2018, 07:21 PM   #5
blazer2007
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Re: Th350 question

I was just going to ask the same question ,first and reverse only. I moved the truck into the garage next day and it and drove it around the block first and it shifted fine. A piece on junk maybe or just the start of a bad gov valve. Just letting it dry out as was raining so will look at things tomorrow but any suggestion would be nice. Not trying to hijack but thought it would be a good place to keep the same problem on one page
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Old 09-30-2018, 07:48 PM   #6
Texasz71
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Re: Th350 question

Absolutely blazer2007.

I just drove my k10. Double checked fluid level, vacuum and the governor. Everything is fine.

When I manually put it in first gear, then drive and i shift it to second, it works.

Also, detent cable isnt stretched. Has good spring back.

Maybe that can help narrow it down?
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Old 09-30-2018, 08:29 PM   #7
Chevyrestorerman
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Re: Th350 question

so are you saying you can manual shift the transmission from 1st to second it shifts, how about rom 2nd to 3rd ? Does it upshift while the manual valve is in Drive ?
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Old 09-30-2018, 08:35 PM   #8
Texasz71
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Re: Th350 question

Quote:
Originally Posted by Chevyrestorerman View Post
so are you saying you can manual shift the transmission from 1st to second it shifts, how about rom 2nd to 3rd ? Does it upshift while the manual valve is in Drive ?
Yes it shifts manually.

It does not upshift unless I manually do it.

Blazer2007 - check your governor, vacuum modulator and fluid level. If all that is good, drop your pan and do a flush
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Old 09-30-2018, 09:06 PM   #9
Chevyrestorerman
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Re: Th350 question

Put a vac gauge on the end of the vac line at the modulator and see how much vac you have.
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Old 10-03-2018, 10:37 AM   #10
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Re: Th350 question

Well I got it all jacked up on blocks { I hate lowered trucks now } First thing I noticed was modulator hose by the tranny was not connected, hose looks bad and soft, would this cause my problem or start looking at the Governor . I,d like to take it for a test drive but is a pain to get the truck down and out and then jack it back up ,thought I would take suggestion first on the disconnected Mod line
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Old 10-03-2018, 01:35 PM   #11
Texasz71
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Re: Th350 question

Quote:
Originally Posted by blazer2007 View Post
Well I got it all jacked up on blocks { I hate lowered trucks now } First thing I noticed was modulator hose by the tranny was not connected, hose looks bad and soft, would this cause my problem or start looking at the Governor . I,d like to take it for a test drive but is a pain to get the truck down and out and then jack it back up ,thought I would take suggestion first on the disconnected Mod line
Replace that little rubber connector. Also replace the one on the intake too. That should rule out vacuum leaks. Also might as well get a new modulator. Governor is on the opposite side of the trans. Round cover about 4 inches in diameter, towards the rear. Push the retaining clip off, pry the round cover off, some atf will come out, be prepared, spin the governor out. Theres a little piston inside it. Move the side wings simultaneously, does the piston move inside? If not, wack it, spray with your favorite lubricant, get it unstuck. Once its unstuck, stick it back in. Next, Check atf level. If it's too low or high, it wont shift.

Was the truck sitting awhile?

If you have done all this, you're in my boat now.

I'm checking vacuum psi today. If that's fine, I'm getting a new governor. If that doesnt work, trans rebuild.

Let me know if you have any other questions broseph
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Old 10-03-2018, 09:04 PM   #12
blazer2007
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Re: Th350 question

Truck driven daily except winter, Got new hoses for tranny line installed today. Will check the Gov. while I,m there . Might do a tranny filter change if time permits .Trying to get my Jeep ready for winter and having some issues . Getting cold for this time of year and it snowed 40 cm. about 10 ins. in calgary yesterday ,not close but has the the same northern air flow. Thanks by the way
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Old 10-04-2018, 07:02 AM   #13
Texasz71
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Re: Th350 question

Quote:
Originally Posted by blazer2007 View Post
Truck driven daily except winter, Got new hoses for tranny line installed today. Will check the Gov. while I,m there . Might do a tranny filter change if time permits .Trying to get my Jeep ready for winter and having some issues . Getting cold for this time of year and it snowed 40 cm. about 10 ins. in calgary yesterday ,not close but has the the same northern air flow. Thanks by the way
Snow??? It was 90 degrees here yesterday...

Check the gov and get back to me.

So at idle I have 17 psi. Which is what I need. I bought a new governor. Should be here by friday. If that's not it....then rebuild it is.

To recap, I have done:
New vacuum modulator
Checked vacuum at modular
Taken governor out and made sure it was functioning
Replaced trans pan - it was leaking and I was low on fluid.
Replaced trans filter.
New ATF
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Old 10-04-2018, 08:43 AM   #14
Chevyrestorerman
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Re: Th350 question

Quote:
Originally Posted by Texasz71 View Post
First post. Long time lurker, first time poster.

So I recently bought my first square body.

1975 k10. 400/350/203

Previous owner said it needed some TLC, and I was ready for a mediocre project.

So right off the bat, the th350 wouldnt shift from 1-2. It had 1 and reverse. So after googling, I replaced the vacuum modulator. It has vacuum at idle. Still no shifty. Next I pulled the governor. Turns out, the plastic gear had broken off. Got it out (nightmare), then put a new plastic gear on. The piston was moving freely. Still no shifty. So I noticed the trans pan was dented and had a slow leak. So I just got finished swapping the pan (one with a drain plug), and added fluid. Fluid level is perfect. Still doesnt shift.

After hours and hours of googlin, I come to yall for other suggestions.

Thanks in advance
When you had the pan off, what was in the bottom of the pan ? Any metal or clutch type of material in the pan ?

Here again, people chase issues on transmissions and want to put the truck on the road not knowing for sure if the truck will leave you on the side of the road. Simply pull the transmission and have it rebuilt. This would eliminate all your worries when you want to drive the truck and if you wanted to drive it 200 miles you can. Its not like its going to cost a arm and a leg....why did you buy the truck in the first place ? to drive it ? you drove the truck before you bought it right ? did it shift than ? so if it didnt shift you knew you were going to have to address this issue....got it cheaper because it wouldnt shift....spend the money and fix it right.
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46 total vehicles in my collection:
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3 - 67 corvettes, 1 - 67 chevelle, 5 - 68 chevelles
2 - 67 Nova SS, 1 - 57 nomad, 1 - 57 belair

Last edited by Chevyrestorerman; 10-04-2018 at 08:50 AM.
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Old 10-07-2018, 09:24 PM   #15
Texasz71
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Re: Th350 question

Got a new governor, slapped it in, and the trans shifts. I guess there was just something wrong with the one I had.

Fixed!
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Old 10-08-2018, 08:28 AM   #16
Chevyrestorerman
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Re: Th350 question

A forum lesson learned. Never trust the information given as far as someone knowing if the part is good or bad. Hey try another governor!!! The gear was changed on the gov right. Broke ?
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Last edited by Chevyrestorerman; 10-08-2018 at 08:33 AM.
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Old 10-09-2018, 08:39 AM   #17
blazer2007
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Re: Th350 question

Quote:
Originally Posted by Texasz71 View Post
Got a new governor, slapped it in, and the trans shifts. I guess there was just something wrong with the one I had.

Fixed!
did you have much trouble getting Gov. cover off , not much room in there ?
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Old 10-09-2018, 08:46 AM   #18
Chevyrestorerman
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Re: Th350 question

Getting the governor out of a 4x4 truck vs a 2wd truck is a little harder because of the Transfer case. Without the transfer case on a 2wd its a little easier to get the cover off, IMO. I am assuming since you said something about a lowered truck its a 2wd and not a 4x4.
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3 - 67 corvettes, 1 - 67 chevelle, 5 - 68 chevelles
2 - 67 Nova SS, 1 - 57 nomad, 1 - 57 belair
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Old 10-09-2018, 07:49 PM   #19
blazer2007
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Re: Th350 question

I just had a hard time getting the cover off , not much room in the fr. section to get a hammer and screw driver in there , back side is better but looking for future suggestions as I want to do my other truck. It,s fine but have a leaky speedo bullet and might as well do everything at once so I don,t have to buy more tranny fluid . This was a messy job ,tranyy leaking all the time when trying to work on it ,slippery tools and no lift. I did everything ,new Modulator ,filter ,speedo bullet , tailshaft bushing and seal . Trouble is everything was near perfect except Modulator hoses. Live and learn but now I know is good till I die
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