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TH-350 Won't shift into 3rd

Discussion in 'The Garage' started by BigJ's K-Blaze, May 21, 2005.

  1. BigJ's K-Blaze

    BigJ's K-Blaze Registered Member

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    Just got everything put back together with the new transmission. 350/350/203 setup. Everything is working ok except the shifting into 3rd gear part. The TV cable is not hooked up to the carb... just hanging there... could this be a problem... or does this just tell the tranny when to downshift, when its on a th-350? Modulator is hooked up... and has enough fluid and everything... just not shifting into third. It will shift 1-2 just fine. Thanks for any help guys, it'll feel good to have everything working after 8 months off the road.

    -Justin
     
  2. diesel4me

    diesel4me 1 ton status Premium Member

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    Tranny woes..

    The "detent" cable SHOULD be hooked up!--however,its not likely to prevent it from shifting into 3rd unless its held in the "pulled" position like it would be when you floor it if it were hooked up..

    You say the modulator is "hooked up"--but to where??--the correct place on the intake??--if you put it to a port on the carb,it might not be manifold vaccuum--you should have a strong suction at idle at the place the modulator is getting vacuum from..."ported" vacuum might keep it from upshifting...so will a bad modulator...could be a stuck valve in the valve body,but not a common dilema..

    Have you tried to "help" it upshift by pulling it into 2nd gear manually,then accelerating and shifting to "drive"??--if it shifts then,its possibly the modulator,or maybe your just in 2nd gear to start with and your indicator is out of whack!...if it feels like it goes into neutral when you let off the gas,then back into gear as you give it gas,the modulator is usually to blame(or its vacuum source is lacking..)...good luck--I hate tranny troubles... :crazy:
     
  3. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    How is reverse? Does it clunk bam as soon as you shift it to R?
    Try brakestanding it in reverse and see if the tires will spin or if the tranny slips. This will check the direct clutches, which is used primarily in D and R.

    Have you played with trying to manually shift it a little past D into N to see if maybe the linkage is out of adjustment and its just stuck in 2nd and not going into D?

    Otherwise It could be the 2-3 shift valve is stuck. :thinking: You mentioned its been sitting for 8 months... maybe the shift valve in the valve body is gummed up a little.. :confused: OR is it a NEW transmission like you said?
     
  4. BigJ's K-Blaze

    BigJ's K-Blaze Registered Member

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    Sorry for not clarifying, the tranny is junkard new. It was pulled from a running truck. Everything looked good after we took the pan off. The fluid was even nice and red. The clutches seem to hold fine. It's seeming more and more like its a valvebody issue. Im going to redo the vacuum line to the modulator and get the detent hooked up. Thanks for the help.

    -Justin
     
  5. Dave1

    Dave1 Registered Member

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    After a recent engine install the mechanic had my vacuum lines run all wrong. The vac line from the T-400 modulator was run to a carb vac port and the trans was shifting very quick and hard.

    I moved the vac line to the manifold vac port right in front of the dist on the intake and the trans than shifted fine and like normal.

    Shifting from first to second OK, but not shifting into third gear? ............the linkage is susspect. Can you manually shift from 1-2, 2-3 and feel the linkage firmly shifting?

    Check the easy stuff out first.

    Dave
     
  6. gzzgfw

    gzzgfw 1/2 ton status

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    Take the vaccuum hose off the modulator on the back of the tranny. Inside the modulator through the hose opening is a set screw (need a small precision screw driver). Might need to turn this in or out until it starts shifting into third.

    I had one built and it didn't shift up so when i called the transmission builder he informed me of this mod. Good Luck
     

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