Last April, I had an issue regarding the Merc-O-Matic and its hard shifting going from 2nd to 3rd. The resolution was to lengthen the throttle linkage on the side of the transmission. As I proceeded to lengthen the linkage, the shift point from 2nd to 3rd became higher, the kick down engages with less throttle and the torque from 30 mph to 50 mph increased dramatically. It almost seems like the transmission was fighting the engine. Is it possible that the transmission was holding the engine back? After the adjsutment to the linkage, when the transmission has shifted from 2nd to 3rd and then when I allow the speed to drop down to 30 mph with it still in 3rd, there is allot more power and faster acceleration (low end torque) when accelerating from 30 mph to 50 mph+. Any insight as to just what the adjustment does? I am trying to understand what I am doing rather than just blindly adjusting the linkage until the issue resolves it's self. Even though there is something to be said for that too!
the Merc-o-matic is the same as the Ford-o-matic right? It's the 3 speed that has only 5 shifter positions. P,R,N,D,L. if this is right I'm running it in my '30 behind a 292. The linkage you are adjusting is the Throttle valve linkage, it changes the pressure depending on the throttle position this changes how the transmission shifts. The correct procedure for adjusting is to use a gauge and hold the throttle at differant positions and adjust rod for correct pressure. You will have to check a Motor manual for the numbers, or I think you can find it on the net with a search. I know that you will want this adjustment correct as damage may result from just turning the screw. The problem I'm having with mine is that the trans does not want to down shift under closed throttle, like when comming up to a light. It will wait untill the car is allmost at a stop before it drops to 2ond. that and it up shifts too soon. hope someone chimes in with more info
You are correct the Ford-O- and Merc-O look to be the same. I own the Transmission service manual (51-55 Mercury - Lincoln) and the discription as to the Low Upshifts: Throttle linkage too long Throttle lever bent Valves sticking in control valve Internal leak in control valve Rough 3-2 (closed Throttle) Downshifts: Throttle linkage too short Bands out of adjsutment Front servo sticking Valves sticking in control valve ***embly Internal leak in control valve "down shift from High to Intermediate (3rd-2nd).....downshift should occur from 11-3 MPH"
Shift timing and shift firmness are determined by the balance between throttle valve pressure and governor pressure. What you're adjusting controls the throttle pressure, which is half of the equation. Remember that there might also be something amiss with the governor pressure, which ideally increases and decreases with changes in wheel/road speed. I'm ***uming that these "-o-matic" trans don't use a vacuum modulator. Also remember that some transmissions might require multiple hydraulic events to complete a gear change. For example, first gear may require a clutch to be applied. Upshifting to second gear may only require that a band be applied. But third gear may require that a band be released and another clutch be applied simultaneously. The timimg of these release and apply events is critical. An internal problem in the trans or valve body can affect the timing and duration of these events and make the trans feel like it's holding itself back. Again, I'm only guessing that the Ford or Merc-o-matic transmissions may work in this manner.
"I'm ***uming that these "-o-matic" trans don't use a vacuum modulator".....appears to be a hydraulic spring loaded valve
thanks Merc-cruzer, I guess my 3-2 down shift could be about 3 to 5 mph so that may not be too bad. guess I could try to get that 2-3 shift higher be adjusting the rod. have you found that manual on-line?
Your transmission only 'transmits' power, and can only multiply AVAILABLE torque, not create it. The first thing to consider is, your engine does not produce either horsepower or torque in the same quan***ies from idle to peak rpm. And horsepower and torque are two different things, as suggested by the fact they have different names. Most engines, especially from the era of your Merc, produced max torque at mid range rpm and peak hp at upper rpm's. When you changed the shift point of the transmission to a higher engine rpm, the engine rpm was producing more of both hp and torque and you felt that in improved acceleration. That would be a double benefit, so to speak, because it kept the trans in 1st gear longer, taking full advantage of the favorable gearing for acceleration, and raised the vehicle speed considerably before shifting to 2nd. And, when it did shift to 2nd the rpm was higher in the power band because the rpm drop that occurred with the shift wasn't to such a low rpm as before and more power was available for 2nd gear acceleration. The same thing for 3rd gear. No magic to it, nor an indication of a faulty transmission, beyond improper adjustment, that is. Ray
It seems that the adjustment has provided more "available" torque through a broader band of speeds, most notably at lower speeds. Thank you, Roy
The torque converter has a say in torque multiplication. When starting out from a dead stop the torque converter multiplies torque. As the engine speed gets higher the torque converter does less and eventually just transmits power. Now if you are going at a slow speed with the transmission in 3rd, the torque converter will be multiplying torque, where as if in 2nd at the same speed, the torque converter will be doing less torque multiplying, if any. So your torque feeling is not far fetched at all. The TV rod, along with governor provide upshifts and downshifts, so don't discount the governor being out of whack.
The answer is, shorten the throttle linkage rod, by screwing in adjuster “U” bracket on the top of the rod, down until the issue is resolved. This will take a few adjustments and test drives until you are successful. The rod is located on the driver’s side of the transmission and connects to the throttle linkage behind the oil filter housing.
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