[OldDiesel]

Ok, my truck has been parked for a few weeks now because the tranny was acting up. What it was (is) doing, is not shifting properly. It will shift, but only at the extreme upper end of the RPM range. Now, because of my work schedule and limited funds, I've decided to put it up for sale and disclose that I think it needs a transmission and take the loss on the value of the truck. However, in talking to a guy the other day, he informed me that there is a transmission vacuum modulator on the outside of the trans that can go bad and in some cases just come unhooked that will cause exactly my symptoms. Plan is to go under the truck today if the weather holds, and find this modulator and attempt to correct the offence. Anyone ever dealt with this before? I'd really like to get this fixed so I can drive my truck again.

 

[Davandy]

Yes I have on a Chevy truck C20
The thing was so busted it was sucking oil into the engine.
You can try to replace it the cost is minimum.

This is it.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=BMM-20234&N=4294925134+4294839071+4294815988+4294904018+115&autoview=sku

 

[OldDiesel]

Well, found the modulator valve, the part was twelve bucks, and took a grand total of 45 seconds to replace. Good news it that I can drive the truck around locally now, but I still seem to have issues with higher speeds. It seems like my poor old truck just doesn't have third gear any more. Now here is the funny part... If you manually pull the shifter down, there are distinct 3-2 down shifts, and 2-1 downshifts. Maybe my torque converter has gone bad?