Auto transmission slipping (or something!)

Car is a Mav 1975, 6 cyl 250 cu in automatic.

For the last three days, I have noticed that the thrid gear doesn't come on at around 24-25 MPH as it always had before, but rather it takes from 30 to 33 or even 34 MPH before it shifts into third gear. This is very scary and very irritating.

There's more: when on flat level ground it does as above, but if I'm going uphill, it gets worse (even higher speed before it shifts). But if I'm downhill, it will generally shift into third at around 24 to 26 or 27 MPH.

The ATF level is normal.

What could be the problem?

 

Thank you, Don, I will!

 

Does anyone else have any other ideas?

 

Comet Fever hit it pretty dead on. Replace your vacuum module. They're easy to replace, and about 10$ or less from Napa

 

Can Lzoesch or Comet Fever tell me where exactly is the module? I look but I just can't tell it apart from other things. Not too mechanical, that's me!

 

or


Looks like



here is a tutorial for a mustang, but C4's are C4's regardless of which car model. Although, they vary briefly between inlines, and V8 applications -- they're generally the same thing and is very simple task at hand.

http://www.mustangmonthly.com/techa...e_ford_mustang_c4_transmissions/photo_18.html

When I replaced mine, I also replaced the trans fluid, and the seal for the cover.

 

Here is a link to a similar thread for what you're asking and it even includes the link to orielys for a 74 mav

http://www.oreillyauto.com/site/c/d...=Search_C0073_1132209_2212&pt=C0073&ppt=C0338

here is maverick forum thread

http://mmb.maverick.to/showthread.php?t=82480

 

And last post -- I swear haha

Here is a step by step how to adjust the screw if needed

http://www.ehow.com/how_8049803_adjust-modulator-valve-ford-c4.html

 

Thank you so much, you guys are awesome!

 

Before you start swapping a bunch of parts, FIRST check for a vacuum leak.

 

More than hoses leak...

 

I still can't find the transmission modulator on my Maverick. Is it inside some other contraption,, so I have to remove it, like inside teh fluid pan or something? I looked all over the passenger's side underneath the car and nothing.

I haven't driven it practically since this whole thing started. I really need help. guys.

 

Look on the passenger side of the transmission. Above the transmission pan. It will have a vacuum hose on it. If it's a 72 it will not screw in it will have a clip that holds it in. The clip will bolt to the transmission.

 

Question, I removed my 200 I6 from my 71 and installed a 351W, would there have been a vacuum module on the C4 for it? The transmission is slipping terribly. When driving my car I literally have to shift it like a manual going from L1-Drive to drive the car. The transmission was fine before I swapped the engine.