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just swapped in a th400 and no upshift.

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k5blayzer

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Location
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vehicle: 89 TBI 350 k5 blazer.

original tranny and t case: 700R4 and np208

swapped in: th400 and np205.

here is the problem, i pulled the old junk 700r4 out and tossed in a th400 that had supposedly been rebuilt. i pulled the pan prior to install and everything was clean and looked mint condition.

i just took it for the first test drive and it wont come out of first gear. reverse is fine and it cycles between forward and reverse without issue. but it just wont up-shift!

i ran a vacuum line to the modulator from a source i found on the firewall. i used rubber tube, which im now reading can cause issues. but can it cause it to not up-shift all together? or is something else wrong here?:dunno:

i read about the governor possibly being stuck- where do i find this? could someone elaborate? cheers!:bow:
 
Did you hook up the kick down wire or do you know if it has a manual valve body. If it has a manual valve body then try shifting it manually, it should work. This is the only way a manual vb will work. Then again if you did not hook up the kick down solenoid it will not shift at all. This solenoid has one wire running to it on the driver side that runs to a switch on the excelorator petal linkage. I believe it has power full time until you stomp down on it it kills the power to the solenoid which adjusts the pressure through your valve body.
 
i thought that the kick-down circuit worked opposite as you say? i do not have the kick-down wire set up yet but i heard they work fine without, is this untrue on some years?

yes i tried working through the gears with shifter, it doesn't make any difference for me..
 
Your problem is the vacuum source, you need full manifold vacuum. I'm sure if you took the vacuum from some hose on the firewall that it IS NOT manifold vacuum. There is a vacuum source at the number 8 intake runner and you'll need to get a fitting for that thread size and for the hose size you're running to the modulator valve. I would also suggest you run a piece of steel tube from the intake down to the trans and only run a short piece of vacuum hose at each end to make the vacuum connection.

The "electric solenoid" is nothing more than for passing gear and DOES NOT need to be hooked up for the trans to work properly (other than it won't downshift when you mash the gas).
 
this is the feeling i had, bad vacuum. could you elaborate on the numer 8 vac rail you speak of? like where exactly that is? im no mechanic but i try!:woot:
 
There is a tapped hole in the number 8 intake runner (rear passenger side last intake runner). The hole should be 3/8" NPT so you would need a 3/8" NPT to probably 1/4" vacuum hose fitting. I just took a look at my spare 89 TBI intake manifold and it is there 100% for sure. IIRC there is just a plug in the hole currently as nothing is used by that vacuum source.
 
thanks for the speedy replies, i will try and change this all tomorrow and report back.. does anyone have a pic of this solid line i need to build just so i can get a general idea? do these usually come from factory with solid lines?
 
It's easy to bend one up from a solid piece of steel brake tubing. Use a good thick rubber line at each end over a flare in the tubing and a little zip tie over the connection for insurance.
 
Even with no vacuum,you should be able to coax it into upshifting by manually pulling it into low and shifting into second and third manually,though the tranny wont seem to act right without vacuum,it'll feel like it goes into neutral when you back off the throttle..

The govenor gear might be stripped ,its only nylon and pretty fragile,or the valve in the govenor may be stuck--its easy to check,the govenor is under a steel cover that usually is just a friction fit on the side of the case,some had a wire bail like your master cylinder doesto hold it on--pry the cover off carefully and you'll see the govenor weights,pull it straight out and inspect the gear,and see if the sleeve valve inside the govenor is free to move when you open the weights--a little brake cleaner will work to flush any gummy goop out of it..

I bought my '81 Chevy G10 van in 1990 for 500 bucks in nice shape,because it had a stripped govenor gear and the owner thought the tranny was "junk"..got it for 500 bucks with 138K on it--I got a used govenor from a junkyard tranny and popped it in,and it shifted perfectly,all it had was first and reverse before..I drove that van to TN and countless other far off places and never had another tranny issue,it has 178K on it now!..
 
how the heck do ya adjust the linkeage on these things? reverse lights are on when it in drive.. and it grinds when u try and shift into park!:dunno:
 
Disconnect it from the trans and manually shift it Into park with a screwdriver or something. Then Put the column in park, and make it fit with the linkage adjustments.
 
Without the proper vacuum source, the trans will think the engine is at WOT, except for kickdown solenoid in your case. So it should shift, just higher RPM. However, if your linkage is not correct, that could be the problem as well. I hope it's the linkage or the governor, and not the clutches. Good luck.
 
i hope so to, we shall see.. the kick down switch is yet to be installed so i guess i will grab it tomorrow.
 
The t400 will up shift fine with out the switch, it just won`t down shift when you floor it. I didn`t have a switch for mine for over a year. Good luck with it.
 
4X4HIGH said:
There is a tapped hole in the number 8 intake runner (rear passenger side last intake runner). The hole should be 3/8" NPT so you would need a 3/8" NPT to probably 1/4" vacuum hose fitting. I just took a look at my spare 89 TBI intake manifold and it is there 100% for sure. IIRC there is just a plug in the hole currently as nothing is used by that vacuum source.
Click to expand...


mine seems to be taken, along with the rest:doah:
 
are these things available at auto parts stores? or are they dealer only? is it ok to tap off of the line coming out of that fitting?
 
k5blayzer said:
are these things available at auto parts stores? or are they dealer only? is it ok to tap off of the line coming out of that fitting?
Click to expand...

Most likely you'll end up at a junk yard and pull one from ANY kind of vehicle that has the proper amount and size of ports needed.

As for tapping off one of the other hoses that are there I have no idea what is connected so I can't say for sure.
 
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