CUCV M1008 - Bypassing vacuum regulator

[jgb680]

Three days ago my truck was shifting a little hard, so I decided I would change the vacuum modulator. It drove a lot better for about an hour after that. Then it started shifting harder than it was before I changed it. After this I decided to replace my vacuum hoses and it still did the same thing. I then decided to bypass the vacuum regulator. Now when I start out from a stop it sometimes starts in 3rd gear. I was wondering if this is normal operation? Again 3 days ago my truck was driving fine just shifting a little hard...

 

[Cucvnut]

your truck wont run right with out the vacuum modulator. you need to run that. have you searched for hard shifting on here? lots of threads about it. have you changed the filter and done a fluid change on the th400?

 

[jgb680]

I still have a modulator on the truck, I bypassed the vacuum regulator on the side of the injection pump...

 

[Cucvnut]

that tells when your truck will shift. have you made sure the connector from the hoses to the the regulator is not cracked and bad?

 

[jgb680]

I have checked it all

 

[tdfontaine]

have you tried adding a can of Sea Foam then changing the fluids? That helped my tranny shift a lot better.

EDIT: I also changed the filter too.

 

[jgb680]

a little less than a month ago I changed my fluid and filter

 

[jdeoliveira74]

You will not shift right with the vacuum bypassed it has to be connected hard shifts something may need adjusting but the th400 shifts hard to begin with. Did you try to adjust the modulator. Mine is pushed all the way towards the firewall the one on the ip pump! Also check vacuum lines to the transmission

 

[mikelee]

Article in manual has a step to setup. For proper shifts just need to make a gauge block for setting gap. And use a vaccum source for setting (I used a vaccum generator) Like the one Harbor Freight sells well worth the time to do this.

 

[jgb680]

I ended up having to adjust my vacuum regulator and my new modulator. Now everything is working correctly and shifting like it should