Fmx transmission2-3 shift

[Terpatin]

Hello

Whats wrong my fmx transmission, when i accelrate hard transmissin not shift 2-3. When i off pedal then shift to 3rd gear..

 

[Fabrice]

[Whats wrong my fmx transmission]

Its a 50 years old transmission. If it's never been revised or long ago, there are tons of stuffs that can lead to this.

Can be a tiny bit of dirt jamming one valve into the valve body or clutches loose way beyond clearance specs..

I'm not a trans specialist at all. Far from that, but I do have a FMX in running condition, serviced minimum stuffs like the pump and just rebuild my 71 C6.

So with that tiny trans guts knowledge, if of any help, that's what I'd do:

Start by making sure you have the right fluid ATF-F at the right level (trans needs be hot and level checked while running in park)

before fill, smell the oil at dipstick. If it smells like no oil should, burned or sometimes even like fish.

No need to search further, fill it to level and be gentle with it, till you get the parts or a shop, as the trans needs be revised.

As it operates and shifts,

When you are engine running and go from reverse to D and once engaged back to R. Does it shifts in less than a second while engine idles or does it takes more time?

I'd look first if the modulator is well connected ( if not connected at all, the trans could slip a bit even make weird noises)

You can also (carefully, not damaging the gaskets) inspect the servos and clean everything in there. The piston seals or entire units can become hard loosing their sealing properties.

If the trans is in its "juice" for decades, I'd bet it's a piston o-ring that is damaged, where it seals when pressure isn't too high but leaks under higher pressure.

probably also because friction plates lost their thickness forcing the piston to travel more.

On my c6, never serviced, which ran 25 years ago before the car was parked. I saw that because of the heat caused by friction, the plates were very thin and blue, and because of the heat, the inner o-ring of the forward clutch piston was damaged, burned/cut. It stayed in place because it can't go anywhere trapped in its groove. So trans would operate, but because of the leak, the piston would not set the clutch under the full right pressure, causing slipping, which causes heat and wear on the plates, making the situation a bit worse every time. It likely leaded to similar situation as you describe for yours. Which unfortunately also means the trans needs to be revised.

 

[turtle5353]

Check modulator.

 

[Don C]

+1 on the vacuum modulator, start there and kickdown adjustment.

 

[Hemikiller]

Might be absolutely nothing wrong with it.

WOT 2-3 shift point on an FMX car is going to be in the 70-80 mph range. These FMXes were only installed behind 351-2V and 302-2V cars, which all had 2.75/2.79, 3.00 & 3.25 gears. Take a look at the attached shift speed matrix for a C6. FMX will be very similar.

 

[rvrtrash]

I'll add to make sure the shift linkage is adjusted correctly. If it's off a little, the shifter may say "Drive" but the lever on the transmission might be between 2 and 3. Cheap easy check, no parts to buy.

 

[NewAgeMuscle]

Had a similar problem with my car except would almost seem stuck between gears... Was a weird sensation turned out to be my kickdown rod.

 

[Terpatin]

Thanks to the answers.

Vacuum system and pressure cheked and modulator and governor. 

Yesterday i removed the  sump and ther are only 1.5 L oil   

My oil stick has something wrong. Now i waitin it i can test drive.

 

[Vicus]

Thanks to the answers.

Vacuum system and pressure cheked and modulator and governor. 

Yesterday i removed the  sump and ther are only 1.5 L oil   

My oil stick has something wrong. Now i waitin it i can test drive.

Check also this check ball in upper body of the valve body for free movement. It has to sit in the slightly wider area below its current location. 

 

[Terpatin]

I changed new type-f oils and test drive. Not working. ? maybe i must rebuild it

 

[Don C]

Are you checking it with the engine running and the transmission warm and in Park?

 

[Terpatin]

Yep oil level ok. Maybe second gear clutch pagage slips i think. Sorry my bad english. ? it feels like the car's acceleration stops at full throttle. mystical fault. Can the turbine slip?

 

[machattack]

Thanks to the answers.

Vacuum system and pressure cheked and modulator and governor. 

Yesterday i removed the  sump and ther are only 1.5 L oil   

My oil stick has something wrong. Now i waitin it i can test drive.

Check also this check ball in upper body of the valve body for free movement. It has to sit in the slightly wider area below its current location. 

You hit it right the Ball bearing. That ball bearing is a good probability. I just rebuilt my FMX any dirt or debris will make the bearing stick thus preventing a correct shift. 

These Fmx's are tough cookies....dont give up on the old girl.

 

[Spike Morelli]

Over the years, I haven't found a lot of transmission re-programming kits offered by the aftermarket. However, a company called Trans-Go does offer re-programming kits ( shift kits), for the FMX. I've been running one for some time now and really like it.

I know the question was about a shifting issue, not re-programming, but I just thought I'd insert this bit of info, just in case somebody is considering a trans hop-up in their overhaul.

 

[Gregaust]

Thanks to the answers.

Vacuum system and pressure cheked and modulator and governor. 

Yesterday i removed the  sump and ther are only 1.5 L oil   

My oil stick has something wrong. Now i waitin it i can test drive.

Check also this check ball in upper body of the valve body for free movement. It has to sit in the slightly wider area below its current location. 

That's interesting . Does that cause a 2-3 delay? 

O.P be good to know what you find . Does it shift ok at normal acceleration? Is it only W.O.t? Did you try if so back off the kickdown some ?