HELP, Still havin' TH350 problems

[bouncytruck]

I just finished rebuilding my TH350 and took it for a test run last night. THE D#$% THING WOULDN'T SHIFT OUT OF FIRST! It just held in first and wouldn't shift up. Everything else seems to be working fine (except for a leak between the t-case and adapter ). Anyone got any ideas on what might be causing this. Is it the VAC advance? The kickdown? Maybe a stuck valve in the valve body? HELP!

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'69 K-5 Blazer - 350/TH350, 6" lift, 35" tires
Bothell, WA

[BigDave]

You've covered everything that I would check. Dunno what else it could be unless your selector on the tree is in not in sycn with the tranny.

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1972 Chevy Blazer 2WD - 400 SBC, bored, ported/polished heads, 9.5:1 dished pistons, Lunati 480/292 cam, electronic ignition, Edlebrock Performer intake, tricked out Rochester 850CFM Quadrajet, long tube headers, Flowmaster 40's, TH350-C with lock-up switch, 2800 rpm stall, shift kit, custom driveshaft, stock GM 12- bolt rear with Auburn Pro Series limited slip 3.73's, 2" drop spindles, 2" drop rear coils, track bar kit, front/rear stabilizers.

1999 30th Anniversary Trans-Am Coupe #1494 - M6, Flow-tech cut-out, Flowmaster, free mods. One of 292 coupes with M6 and in-dash CD.

[tom hand]

Vacuum hose came off the modulator valve,plug it back up. That or the valve is bad. hopefully

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72 GMC Sierra SWB almost finished---- 84 Softail
Olive Branch MS



[This message has been edited by tom hand (edited May 17, 2002).]

[bouncytruck]

Modulator Valve is brand new and the hose is on it. Maybe the hose has a crip in it somewhere?

How do you adjust the Kickdown. Maybe I did it wrong?

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'69 K-5 Blazer - 350/TH350, 6" lift, 35" tires
Bothell, WA

[kaycee]

Yeah what BIGDAVE said you sure it is insync with selector?

[71GMC_3/4T]

Where is the other end of the modulator vacuum line hooked to? Should be to the intake manifold. If you pull the line off the mod, it should have vacuum. Also, you may have the wrong mod in there. I'm not sure how many different ones are available for the TH350.
Hopefully you didn't miss putting one of the little balls in the valve body...

[bouncytruck]

I got all the check balls in the valve body. The vac modulator is the one that came in the rebuild kit so hopefull it it right. There are some slight adjustments on the modulator itself but not enought to compensate for not shifting. I'll double check the line routing but I believe that it is going to the spacer at the front of the carb. Is this not correct? I'll also see if I'm getting any vacuum.

When you say out of sync, do you mean if the shifter is in "park" the tranny is in "park", etc. It is definately going into park, neutral and reverse ok. I'll put it in Drive and disconnect the cable (has a B&M shifter) and double check that it is in "Drive" and not 1st .

What about the Kick Down. Could it be adjusted incorrectly?

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'69 K-5 Blazer - 350/TH350, 6" lift, 35" tires
Bothell, WA

[john]

Mine did that last year and the problem was in the governor. good luck

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67 SWB 350eng th400 3:07 posi tilt&tach PS/P/Disc Brakes old air a/c P/W keyless entry gaylord lid 70swb project truck 350/th400

[Zkast]

If it will not shift no matter how fast you go, the modulator is not your problem. The design of the valve body and line pressures are setup so the modulator valve raises or lowers line pressure depending on vacuum(engine load) .

About the kickdown cable adjustment? that simply boosts the line pressure which causes a delayed shift or forced downshift. It will also be overridden if line pressure is high enough(pressure will be overidden at 40-45mph in 1st). So eventually if run past this point it will go ahead and shift. If its not shifting after that point its likely you have trash in the valve body or stuck valve.

Typically most problems will lead you to a stuck valve or cut seal when installing. Very easy to "shave" a seal when installing.

One good thing though... If its staying engaged in 1st and does not "freewheel" at the normal 2nd range 18-35mph, then atleast you dont have a piston seal or clutch pack problem.

Check the govenor (its quick and easy to pull), Pull the gear, levers and make sure there is no trash in the ball seats. If that doesnt help, sounds like you need to R&R the valve body and go through it again. You did disassemble it during the rebuild and clean all passages right?




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Pictures and more...
Email me
'71 LWB
350/350T, PS/PB
Special options? Yes, RUST... Need some?

Garrett
Olathe, Kansas


[This message has been edited by Zkast (edited May 17, 2002).]

[69 longhorn]

I would look at the govenor.it only take a little pc of crud to bind it......I had the same prob,think I picked up a little trash from the cooler. I had to clean & reinstall the gov...........69

[72MARIO]

Hey How long did you drive it for ? Me and my dad put a Turbo 400 tranny in his 73 he has been keeping it for years . about 2 weeks ago we drained all the fluid out and put a new filter in then up it went hooked it up to the 350 whatever else to the point we took it for a drive and the frig'n thing wouldnt shift out of first we drove around for a few minutes in first then came second we were stuck in second for a another minute then third came up. had to be the scariest thing thinking we would have to pull it out and get a new tranny .

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72 Chevy 350 1\2 leaf springs soon to have ps, pb, 700R 2/4 drop , 88-94 bench ,67 front clip ,Blazer tank flip down tail light gas filler
Filled stake pockets minor smoothing to fire wall and Frame shortened.posible idea of ash tray into cup holder?

[Zkast]

The good ole govenor is the first thing that acts up when hit with debris. Any red rag fibers, dirt and god knows what else is in the cooler will hit the govenor and cause all sorts of problems. no shift... no downshift(stuck in 2nd or 3rd even at a stop)

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Pictures and more...
Email me
'71 LWB
350/350T, PS/PB
Special options? Yes, RUST... Need some?

Garrett
Olathe, Kansas

[bouncytruck]

Thanks for all the input. checked out the kickdown cable and it didn't have any spring return to it so I ordered a new one (be here monday). I also checked out the vacuum pressure and it appears I have none at idle. Today I'm going to try hooking it up to the manifold rather than the carb spacer plate. I'll also check out the govenor to see if it might have some crud in it.

I disassembled the valve body and cleaned it out very well. I let all the parts air dry so I wouldn't get any "rag dust" inside the transmission but it is still a possibility. I guess I won't be taking it on the 400 mile trip to the campground over memorial day. Even if I get it running before then, I'd like to have a few days to test drive it before such a long trip.

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'69 K-5 Blazer - 350/TH350, 6" lift, 35" tires
Bothell, WA

[bouncytruck]

Thanks for all the input. checked out the kickdown cable and it didn't have any spring return to it so I ordered a new one (be here monday). I also checked out the vacuum pressure and it appears I have none at idle. Today I'm going to try hooking it up to the manifold rather than the carb spacer plate. I'll also check out the govenor to see if it might have some crud in it.

I disassembled the valve body and cleaned it out very well. I let all the parts air dry so I wouldn't get any "rag dust" inside the transmission but it is still a possibility. I guess I won't be taking it on the 400 mile trip to the campground over memorial day. Even if I get it running before then, I'd like to have a few days to test drive it before such a long trip.

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'69 K-5 Blazer - 350/TH350, 6" lift, 35" tires
Bothell, WA