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OK blew up the tranny AGAIN.. third time now

22K views 114 replies 18 participants last post by  John Saxon 
#1 ·
1978 Ford Police Interceptor "Pursuit Special"

Blew the Planetary gear... blew it right off the planet HAHA!

anyways its a C6 trans, but why is mine so differant than other C6's?
Basic C6's have 13.5 inch tail shaft... mine is close to 17 inches!

Was told this is a heavy duty Police Special order trans.. basically the old man (who rebuilt it last time for me) told me its a heavy duty truck transmission with a Stage 2 shift kit from factory.

does this sound right to you guys?

this car eats these trannys :eek:

third rebuild in the last 12 summers ive been driving her..
 
#83 · (Edited)
well got the tranny back in and shes mobile again.. Only issue I have is that it shifts differant... differant meaning in "D" she shifts faster from 1-2 and slower from 2-3.. Differant than before!

also when I start off in low or first, then shift to second.. its good.. then I keep accelerating and shift into drive.. it takes like 3 seconds to go into third AFTER ive already put it in drive...

UPDATE==

ok just drove it again.. and from a standing start GIVE-r, she shifts into second at 4000 when it should be shiftn at 4500... how many turns will it take to turn the mod screw and which direction??
 
#87 · (Edited)
here is a pic of my Modulator pin..

how long should it be? My Modulator pin is "1-11/16"... the wire on top is a coat hanger and its very close in size.. was told a welding stick is very close also!

how much longer should I make it?



aaaand also seems like i overtightened the mod bolt... i was snugging it up and she went a lil to far and now just gets somewhat tight... if I tighten up anymore she seems to like.. strip :( any suggestions on that?
 

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#88 ·
I used a nail for my modulator pin. My stock one wasnt the correct length. U want it to have like a 1/16" of preload before its fully installed. And set modulator pin for 13lbs I believe... So it takes 13lbs to push the pin in by using the set screw.
 
#90 · (Edited)
ok great...
I added a slightly longer pin and noticed a change in shift pattern now in regular drive and crusin nicely (higher rpm)... then when I open her up WOT she still shifts to soon... 4000ish instead of 45-4600 like she use too

and another thing..

I have the hose goin from my modulator right to my intake.. Should the hose be connected on the intake or off the carb?

I remember years ago someone telling me that I should be running off the carb and at WOT there should be no vac pressure there!

BUT if im running off the manifold then there will always be vacuum...

anybody??
 
#91 ·
Intake is fine for modulator. Do you have your kickdown hooked up and properly adjusted? Is it engaging the valve in the VB?

There is very little change as far as the modulator is concerned once past about 3/4 throttle which is why you have the kickdown to tell the transmission you are at WOT...
 
#94 · (Edited)
Intake vacuum is fine. At WOT the engine should be at 0 vacuum anyway. U Dnt want it Hooked up to ported vacuum at the carb bc that will cause erratic shifting and issues. If u want the shift to accur higher in the rpm then screw in the modulator. Bit at WOT the modulator is basically useless. I was told lockdown doesn't affect the shift points but then I was told it does and also has an effect on the vb pressures. Make sure the lockdown is adjusted and is only occurring at the very end of the throw at the carb. My lokar lockdown says to set carb at WOT and then pull the kickdown cable as hard as possible and the. Lock down the adjusting nut. So right before WOT the kickdown is being pulled. But I'm not sure if the lockdown is even operating at WOT in 3rd gear as it shouldn't be Down shifting/kicking down at top speed.
 
#97 ·
the kickdown is working, but just at lower speeds than before.

Before rebuild I use to be able to kickdown at 50, now she kicks down at 35ish.. where I use to kickdown at 110+ she only kicks down at 100 now, NO HIGHER.... Am i making sense?

and at WOT, she would shift 1-2 at around 85+, now its around 65

All my shifts have dropped in rpm range :(

(Highway gears on this car) so shes sluggish now as to compared to before when I was in drive!
 
#101 ·
yes it appears to be installed correctly!

As I said, it kicks down BUT at a lower speed than before... it seems like everything is shifting, kickdown etc is all happening at a much lower RPM than before the rebuild.

I use to be able to kickdown at 35mph.. now she only kicks down like that at 20 mph

The car use to shift at wot at 45-4600 rpm... now it shifts at 3900 rpm into second at wot


COULD THIS BE THE CAUSE OF A 3500 STALL converter?
 
#102 ·
Did you actually do the test that I asked? If you disconnect the kickdown linkage and drive it are the WOT "Kickdown" points the same or lower? If the same then your kickdown is NOT working and time to pull the pan.

A higher stall converter will raise the WOT shift point. Your C-6 has no idea how fast the engine is turning. All it knows is road speed (governor on output shaft), engine load (modulator), torque demand - WOT (Kickdown).

Governor pressure works on one side of the shift valves and Modulator + kickdown work on the other. In the most simplistic terms when the pressure on one side overcomes the pressure on the other side the valve moves and a shift happens. Now the factory uses different valve area and spring pressures to modify when shifts occur, as well as a bunch of other valves, springs, and such to control shft firmness.

A VB or governor change can cause a change in shift points as well as its shift curve. Mixing up the springs can screw things up real good too...
 
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