Shifting issues?

[irocjoecool]

Hello guys,

I have an 85 M1009 with the TH400.
My truck seems to shift into 2nd and 3rd WAY too soon.
It also doesn't want to downshift after it is in 3rd gear unless you almost come to a stop.
Truck feels down on power but that could just be the general lack of power from the 6.2
Thank you

 

[Warthog]

The TM 9-2320-289-20 tech manual has a step by step testing procedure for your truck.

Have you replaced all the rubber tubing for the transmission and vaccuum pump? Have you adjusted the throttle position vaccuum valve?

There some very basic items to check. We have discussed this many times.

 

[Vhyle]

I should do this as well. I feel that my shift points are a bit high. I have to accelerate to 55-60 to shift into 3rd, every time.

 

[jacksmad1]

I should do this as well. I feel that my shift points are a bit high. I have to accelerate to 55-60 to shift into 3rd, every time.

It sounds like your vacuum modulator on your transmission needs adjusting. Remove the vacuum hose from the modulator, insert the proper size allen wrench and adjust, test drive, adjust, until you get it like you want it. If that doesnt get your shift points where you want them, follow the troubleshooting guide for further diagnosis.

 

[Keith_J]

Before you go adjusting the modulator, check to see if the vacuum regulator on the injection pump is functioning properly. Tee in a vacuum gauge to the TOP line, then drive and see if vacuum is roughly 18" Hg at idle, dropping to under 2" at wide open throttle.

The regulators are nearly impossible to fix, they are $60+ from various online sources. I got mine from the place named after a big river in South America.

I had the exact same symptoms. Now it is perfect.

 

[Vhyle]

Awesome replies, thanks guys. I'll consult the TMs as well for diag.

Another task to add to the list, I suppose. Hah.

 

[MarcusOReallyus]

Find and fix problems first.


Then adjust.

 

[truck1]

I had late shifting issues with my 1028 and excessive engine RPM's. MY fix was to start engine, pull rubber hose at modulator,put finger on hose and feel for any vacuum.In my case there was none and the rigid 3/8ths line came off in my hand! Followed line to engine compartment and where the line crossed the firewall it contacted same and wore through severing the line. Spliced in a short piece of rubber 3/8ths fuel line with 2 clamps and adjusted away from firewall. Truck shifts quiet and smooth at way lower speed and RPMs,better than it has since I bought it 2 years ago. Check your vacuum lines first!