So my 3 speed auto just stopped shifting into third. Im guessing a shift lever just came undone or something but I havent had the time to spend some time under neath the thing. Where are the shift arms on these things? Any ideas?
not likely a linkage problem .. more likely a vacuum problem .. look for a vacuum leak going to the trans shift modulator ..
Wheres is that located? On the block or trans?
If I may butt in: The vacuum modulator is on the transmission. If it is disconnected or has no vacuum for any reason, it will rev way up before shifting HARD to second (late shift).
mike
Quote from: Pintoman1971 on July 03, 2015, 08:47:32 PM
Wheres is that located? On the block or trans?
It's on the back of the trans on the right side should be a hose on the end of it going to a solid line, follow it and check for a leak.
(http://diyford.com/wp-content/uploads/2013/12/trans.jpg)
it`s the round gold thing at the bottom of the picture .. as lugnut said it will shift once at a higher rpm than normal but will not shift into high if the modulator has no vacuum .
It will shift into high around sixty plus mph , and it will shift hard , Hoss429 , 74 pinto wagon and lugnut are right , you are missing engine vacuum, and more than half of the leaks I found on ALL the cars using the C-4 is the rubber elbow that goes to the modulator to the steel line at the bottom , over the years it get oil covered and turns to a goo or swells up and falls off , or splits , and it can happen on the top also, valve cover leaks and does the same thing to the hose there , good luck, and have a great 4th
Located it yesterday but the internet has been down at our house we just got it back up and running. Luckily i didnt drive it other than a test drive up the road after i put the new head on it and noticed it wasnt shifting into third.. Shifts through all gears now after reconnecting the hose. Thanks you guys are a big help when im stumped with things ;D
The modulator is how the trans senses much higher load like high rpm merge on freeway. When vacuum drops off like with a leak, the trans then shifts at higher rpm and the clutches lock up much harder, why it hits each gear so hard when using low throttle amounts. It thinks you're wanting passing gear all the time. Third still works but at such a high rpm it looks like it's gone.
With proper vacuum the shift points drop way down and closer together and the shifts get much softer at normal driving rpm and load. The modulator essentially adjusts the trans constantly based on the load it is under.
There are literally no shifting arms or levers in an ATX at all, usually only one shaft that opens and closes a manual valve inside the valve body.