Slooooowwww 1-2 on 200R4

[Robert Wilson]

Need help trying to solve slow/weak 1-2 shift. I can also feel a little slip or chatter as band is applying that seems to be worse with more throttle/ power. I have only tried minumum and part throttle due to fear of burning up band.

Transmission was worked on by a general transmission repair shop prior to me workin on it and from the parts list, it has an Art Carr shift kit and .500 boost valve. PR valve and spring appeared stock. Drum and stock band was scorched when I recieved the car.

I installed good used drum, carbon band, and a sonnax servo. Band clearance is .110"

Hooked pressure gauge up saw the following readings:
min TV pressure @ 1000 RPM in Park, N, D is 70 psi.
max TV pressure @1000 RPM in Park and N is 210 psi
min TV pressure @ 1000 RPM L1, L2= 170 psi

TV pressure while driving would climb quickly of idle to 180psi at part throttle and only drops about 5-10psi on any shift.
Couldn't get a max TV pressure while driving as it was too hard to read the gauge and watch where I was going.

So far, I tried the servo with and without cushion spring with no change.
Tried blocking 1-2 accumulator with no change.

2-3 and 3-4 shifts are firm and quick.

Any suggestions?

 

[77 cruiser]

Band clearance sound a little too much, but as long as you have enough travel it should be OK. How are you checking the clearance?

 

[Robert Wilson]

Band clearance sound a little too much, but as long as you have enough travel it should be OK. How are you checking the clearance?

Clearance was checked by measuring servo cover travel.

 

[LOT]

servo shaft

Check shaft just after the taper--I once had one that was (for whatever reason) out of round and was binding. If so it will show with wear marks. What about the 2 small shaft seals, altho I don't think that would cause your problem.

 

[77 cruiser]

Can you tighten it up by .020 or .030 thou.?

 

[JDSfastGN]

Even at minimal throttle angles it doesn't take much slipping/slow apply to burn the band imo. Don't be surprised if the damage has been done already. Just don't want ya to keep making changes when in fact you may fix the problem and no know it because the band/drum are too far gone to show the improvement.

 

[Robert Wilson]

Even at minimal throttle angles it doesn't take much slipping/slow apply to burn the band imo. Don't be surprised if the damage has been done already. Just don't want ya to keep making changes when in fact you may fix the problem and no know it because the band/drum are too far gone to show the improvement.

I should have noted that once I do feel 2nd start to hold, I can go on give it more throttle with a little boost and it appears not to slip and it makes a clean 2-3. Haven't been WOT in 2nd though.

 

[Robert Wilson]

Check shaft just after the taper--I once had one that was (for whatever reason) out of round and was binding. If so it will show with wear marks. What about the 2 small shaft seals, altho I don't think that would cause your problem.

Pin moves freely in bore and I am using stock style split seal rings.

 

[Robert Wilson]

Can you tighten it up by .020 or .030 thou.?

I don't see a good way to tighten the clearanace with the Sonnax servo unless its OK to get rid of the C-clip that retains the apply piston to the servo pin. Anybody left this C-clip off?
Another option would be to cut a new C-clip groove in the pin possibly.