# 350 trans issue



## Hot_Rod (Feb 10, 2011)

When my car gets warm or driven awhile, the trans will sometimes not shift into 3rd and I have to put it in neutral and back into drive to get it back into 3rd and will sometimes downshift back to 2nd on its own. What the hex going on?

I checked the fluid and its bright red and full. My dad thinks it could be a modulator in the trans? Could it be something in the shifter linkage or in the column?

Thanks in advance.


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## freethinker (Nov 14, 2009)

Hot_Rod said:


> When my car gets warm or driven awhile, the trans will sometimes not shift into 3rd and I have to put it in neutral and back into drive to get it back into 3rd and will sometimes downshift back to 2nd on its own. What the hex going on?
> 
> I checked the fluid and its bright red and full. My dad thinks it could be a modulator in the trans? Could it be something in the shifter linkage or in the column?
> 
> Thanks in advance.



start with the governor. they have a plastic gear that wears out


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## Hot_Rod (Feb 10, 2011)

What exactly is a governor? It's not the same thing that controls your speed is it? or is it something else? I dont know much about transmissions, specially older ones.


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## 1970 Lemans (Jul 25, 2009)

Some additional history might be of value. How long (age, miles) has it been since the last rebuild?

A few years ago I had a problem somewhat similar ... that is upshifts were very retarded (only at high rpm), though I don't recall that premature downshift was an issue. In my case, the vacuum hose supplying the vacuum modulator had become compromised. Replacement of the hose resolved the problem. 

Yours might be modulator related ...or not.


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## dimitri (Feb 13, 2009)

Check the vacuum lines on the engine and the modulater. If they are hard and brittle, replace them. If it is still acting up, I would try adjusting the modulator. If you pull the vacuum hose off the mod there is a little adjusting screw that controls your shifting set points. Play with that. If it still acts up, I would replace it.


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## freethinker (Nov 14, 2009)

it is a good idea to make sure the vacuum hoses are good but the modulator should effect all shifts making them late. if 1/2 shifts correctly but 2/3 does not i would suspect the governor.
there is a round steel cover on the side of the trans that hides the governor. just remove the cover pull the governor out and inspect the gear and other parts.


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## Hot_Rod (Feb 10, 2011)

1970 Lemans said:


> Some additional history might be of value. How long (age, miles) has it been since the last rebuild?
> 
> A few years ago I had a problem somewhat similar ... that is upshifts were very retarded (only at high rpm), though I don't recall that premature downshift was an issue. In my case, the vacuum hose supplying the vacuum modulator had become compromised. Replacement of the hose resolved the problem.
> 
> Yours might be modulator related ...or not.


Guy I bought the car from didnt know much about it so miles/age since rebuild is unknown. I checked the fluids and everything and it looks fine.



dimitri said:


> Check the vacuum lines on the engine and the modulater. If they are hard and brittle, replace them. If it is still acting up, I would try adjusting the modulator. If you pull the vacuum hose off the mod there is a little adjusting screw that controls your shifting set points. Play with that. If it still acts up, I would replace it.





freethinker said:


> it is a good idea to make sure the vacuum hoses are good but the modulator should effect all shifts making them late. if 1/2 shifts correctly but 2/3 does not i would suspect the governor.
> there is a round steel cover on the side of the trans that hides the governor. just remove the cover pull the governor out and inspect the gear and other parts.


It sometimes affects 1/2 shift as well, its sometimes slow to shift and will turn some rpm's before it shifts. 

It only really acts up when its been sitting/idling/driving awhile.
Cold start/driving it shifts quick and normal. :confused


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## Thumpin455 (Feb 17, 2010)

If it is dropping out of 3rd and going into 2nd at a steady cruise you are getting dry clutches. In other words there isnt enough fluid reaching the direct clutch to lubricate it and keep it applied. A number of things can cause it, but the big one is a clogged filter, another is a weak pump, and an internal leak can do it too. All of these create low line pressure, and a number of things can cause that other than what I mentioned. If the modulator goes out, it will not shift until the governor kicks in. If the governor has teeth missing or the gear is stripped, it wont shift at all.

Since it shifts fine when its cold, then its looking like it has too much clearance and when the fluid warms up it isnt as thick, that lowers line pressure and causes the erratic shifting. If you had a kit with the seals and clutches in it, and you were closer than Texas I could rebuild it for you in about 4 hours. They arent hard to do, with a book or a video you could probably do it yourself if you can get the apply pistons out, they are held in with a snap ring and a bunch of small springs. I have a small press I use to get those, but then again I do lots of transmissions compared to most people.


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## 66tempestGT (Nov 28, 2009)

any time i have had issues with an old 350 the first thing i do is change the filter. very good results more often than not.


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## Hot_Rod (Feb 10, 2011)

Very good info guys, thanks. I'll definatly look into some of these things. It's odd, sometimes it does it sometimes it doesnt. Mainly when its really warm and been drove awhile is when it does it.

What's all involved and how do you go by replacing the filter? Is it hard? Can a shop do it for a decent price?


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## likethat (Oct 5, 2007)

You can. Just get the car up in the air with jack stands. Take out all the bolts from the tin cover/ trans pan on the bottom of the trans. Watch it, it has about 5 quarts of trany fluid that is going to come out. You need a very large, as in width and length, drain pan and you can leave a couple bolts in by the motor so it will drain out slowly into the drain pan and not all over everything. Once in there you will see a metal or maybe even a plastic frame with some kind of paper/ felt or plastic mesh like material on the bottom. That comes out it might have a couple screws holding it. Here is a pic of both.








once you get it all out clean every thing well with shop rages. Try not to leave any lint on things. Next when you are cleaning the pan there might be a magnet inside that will have fine shavings on it. Just be looking when you pour out the oil for any chunks and excessive shavings in the oil or bottom of the pan. Clean everything and the gasket area's till it is free of all gasket material, oil, and shavings. Reinstall the small gasket for the filter, the filter and 2 screws, then a couple of bolts and the pan + gasket. Get all the bolts going but do not tighten any more then finger tight. Once every one is in there start with one in the middle and criss cross from the middle out till you have every one tightened and you just need to see the gasket squeeze a little when tightening. Then move to the next across bolt. Once that is done I would go over the same pattern one more time with just a bit more turn but not very much to make sure they are all tight, and have not been loosened by the others getting tighter. Now add 4 quarts of dextron type or compatible tranny fluid in the dipstick tube for the trans with a funnel. Once all 4 quarts are in, start it up, shift into reverse and back to drive a few times. Why running and in park, check the dip stick after cleaning it, and see how much oil it needs. If it is at the line closest to the tip of the stick it needs a quart. If it is under the cross hatching area it need 1/2 quart or less. Try not to get it over the top fill line.


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