M1009 transmission th400

[suggsdr]

Hey guys I am have transmission issues.I have read & search till my eyes hurt.Here is what I have done so far.

1. replaced modulator
2. replace filter & fluid
3. replaced hoses

What its doing is hanging up in 2nd when it acts like it shifts its like its caught between 2nd & 3rd sometimes when I can get it to shift its pulls fine.I check the vacuum at the modulator & I am getting 2". at the regulator on the IP its 2" all checks done at idle. seems like the 2" is low.I can't find any info in the TM on the specs as far as vacuum reading.Has anyone run into this before?

 

[Warthog]

You can't get a correct reading at idle. The TM has a step by step procedure to check the correct vacuum reading.

Here is my tread with pictures.

http://www.steelsoldiers.com/cucv/50568-cucv-throttle-vacuum-valve-adjustment.html

Sound like it needs a possible rebuild.

 

[jdeoliveira74]

My truck was doing the same thing when I got it. Can you shift manually thru all gears?? Check the vacuum line make sure they are connected correctly also check the one going to transmission for leaks or holes...

 

[chevyCUCV]

Your vacuum is way to low. It should be 20" at the pump and 8" at the transmission i believe
I only know that because it has been posted here a bunch.

I just found it in the tm's, -20 page 198. Transmission Vacuum valve replacement

Use the manuals!!!!

 

[Warthog]

Your vacuum is way to low. It should be 20" at the pump and 8" at the transmission i believe
I only know that because it has been posted here a bunch.

I just found it in the tm's, -20 page 198. Transmission Vacuum valve replacement

Use the manuals!!!!

The pump should always be putting out 20" of vacuum. The 8" of vacuum at the valve is at partial throttle. The vacuum at the vavle is variable depending on the throttle position.

 

[Dave Kay]

Go under your truck and lay next to the trans ON THE DRIVER SIDE. Look for a wire that plugs into the side of the trans case. Disconnect that wire and test drive. Does it shift now?

 

[suggsdr]

Dave Kay
I have tried that also.I think that my Vacuum pump on the back side of the engine may be bad.I'll check that next but it will be Monday before I can get back on it I will post what I find wrong.When it shifts from 2nd to 3rd it kind of acts like is is between gears like it slipping but if I play with the gear shifter 2-3 back & forth I can get it in 3rd & it runs fine.hard to explain the way its acting.

Thanks

 

[Dave Kay]

Dave Kay
I have tried that also.I think that my Vacuum pump on the back side of the engine may be bad.I'll check that next but it will be Monday before I can get back on it I will post what I find wrong.When it shifts from 2nd to 3rd it kind of acts like is is between gears like it slipping but if I play with the gear shifter 2-3 back & forth I can get it in 3rd & it runs fine.hard to explain the way its acting.

Thanks

Roger that. Have you checked the TM's for the shift lever linkage adjustment? Improper adjustment on shift linkage can cause trans to go in between gears and not up-shift properly. This can also waste your trans in a fairly short time.

Also, that wire on the side of trans goes to another device under the dash, can't remember if it's on the gas pedal or ??? Check that out in TM's as well.

 

[suggsdr]

Follow up

I Checked the Vacuum pump at the regulator & had a good vacuum( rev the engine) & it showed good so I guess it will have to go to a transmission shop.I don't have the help or time to pull it my self.( Warthog was right on the money( post #5).

Thanks to all replys.

 

[ranchhopper]

Its probably the vacuum shift module on the side of the IP mine did that until I replaced it doghead had some brand new ones at a good price thats where I got mine.

 

[ryan77]

Mine was doing the same thing, i replaced the vacuum module like kevin said got one brand new gm part for $75.00 off ebay! My other blazer wouldnt shift from 1st to second i pulled the valve body and cleaned it had a stuck spring and piston!

 

[chrisknight_1985]

Sorry guys i may be posting this on in the wrong place, but i think ya'll can help me. On the passenger side of the trans, front right corner just above the transmission pan, then is the round looking thing plugged into the trans. Can somebody tell me what that is? I change my trans pan gasket, and noticed that there is a little drip coming from it, so if somebody could tell me what it is so, or even better a part number that would be great. Im sorry that i can't describe it more clearly. thanks in adavance

 

[Warthog]

That is the vacuum modulator valve. There is an o-ring that can be replaced.

If you don't know what the part is, look in the TM 9-2320-289-20P or TM 9-2320-289-34P parts manual for the general item you are working on (transmission) There is a parts breakdown with the items numbered. Below the picture is a listing of the parts with a name.

For this item, look at the TM 9-2320-289-20P, Figure 58

You do have a FREE copy of the Technical Manuals don't you?

If not www.jatonkam35s.com has them. Look under CUCV manuals

 

[chrisknight_1985]

i have the Original TM's In the black binder. I found a picture of it right after i made the post and realized that's what i was looking at. Would it be a good idea just to replace the whole thing?

 

[epitts]

i have the Original TM's In the black binder. I found a picture of it right after i made the post and realized that's what i was looking at. Would it be a good idea just to replace the whole thing?

Yup, they don't cost much.