Early shifting auto.

[Benz Dr.]

My problem is the transmission shifts up and down properly and the kick down works. It seems to shift up too early and into high gear at about 90 kph regardless of how much throttle I use except for kick down. Throttle is going wide open so that's not it. I haven't looked at vacuum yet.  My info is that the trans was rebuilt.

Anyone run into this problem and what did you do to fix it?

[Cees Klumper]

My Bronco started having this problem last week after we re-attached the vacuum line from the intake manifold to the transmission pressure modulator that had popped loose. As a result of which it was not upshifting at all anymore. Reattached it and now it upshifts too soon. I need to check on this, but am pretty sure these issues are usually vacuum pressure related. The pressure modulator on the MB trans is adjustable as far as I know so it should be a relatively easy fix if that is the issue. Of course I am just an amateur so am grateful for others to weigh in.

[Nicolas Aristodemou]

I would also think it is a transmission pressure issue. If the engine vacuum to the modulator is present and correct then it could be that the transmission pressure is probably low. It can be measured and set correctly as described in the technical manual under automatic transmission, or easier still is to try an increase the pressure on modulator by turning the adjusting screw 1-1.5 turns clockwise. Make a mark of the original setting so that you could always revert to it in case it doesn’t have the anticipated result.

[ja17]

Yes, I am in agreement with " naristodemou" , try a bit more modulator pressure.


 

[Benz Dr.]

Will do and report back with results.

[FresnoBob]

Hi Benz Dr.

I built a transmission modulator pressure gauge setup that I'm happy to loan you.  I'll ship it to you if you'd like. 

[Benz Dr.]

Thanks Bob. I'll let you know if we need it.