Diagnosis Please - Tranny shifting too fast

[excobraguy]

87 GN with 200-4R. I just changed the stall converter from a 2800 to a Pro Torque 3200-3500 stall. I installed a new filter, 3 qts. of Dexron/Merc III and 6 or 7 qts of regular hydraulic tractor fluid, not the Mobil 424 (couldn't find it!).

So theres the setup, now the problem definition. The car with the 2800 stall had no shifting problems, all gears ran out nice and it shifted fine, but overderive did not work. It originally had regular tranny fluid. Now with the Pro Torque converter under WOT it shifts to 2nd and then to 3rd way too fast, the rpms are around 3000 on the shifts. It does however, go into overdrive where the 2800 didn't. Also, when around 35 mph and in second gear, I used to be able to hit WOT and it would downshift, now there's nothing...it just lugs until it shifts to third. Could the extra thickness of the tractor fluid be causing it to shift too early? It seemed a lot thicker than the Dexron III. The hydraulic fluid is Allison C4 rated and I read somewhere that this was OK for our trannys. I plan on changing the fluid this evening when I get home from work back to straight Dexron III. Does anyone have any other inputs based on my description? Is it the new converter? Are there computer settings that need updated with a converter swap? Oh, I also reset the TV cable thinking this might help, it didn't.

Thanks guys.

 

[excobraguy]

TTT Anyone??????????

 

[77 cruiser]

How did you set the TV? Is it back to the same position as it was before you swapped the conv.?

 

[excobraguy]

How did you set the TV? Is it back to the same position as it was before you swapped the conv.?

pushed in the D shaped lock, pushed the black stop all the way back Pushed the throttle to WOT and heard about 3 clicks..........

 

[excobraguy]

Has anyone experienced weird shifting problems with the tractor hydraulic fluid?

 

[Real-T]

pushed in the D shaped lock, pushed the black stop all the way back Pushed the throttle to WOT and heard about 3 clicks..........

Is the TV cable stopping the throttle arm from going WOT?

I would guess that based on the fact you can cruise along at 35 mph and go WOT that it doesn't downshift would mean that the TV Cable may be too tight.

I would loosen the cable a couple clicks at at time until you can get it to down shift. Some cable assemblies are so tight that using the throttle to get it to self adjust may not be enough and you may need to help it by pushing in the "D" tab. But don't loosen it too far as this will cause too late shifts and low trans. oil pressure in all gears.

 

[Blazer406]

I'm confused.....

You had a tranny that had no OD..... then you changed the converter.... and now OD is there... but it shifts too early....

IMHO you have other tranny issues... and I wouldn't have put the stall converter in there without figuring out what was wrong... that kept it from OD.

Maybe someone else can be of more assistance.

 

[excobraguy]

I'm confused.....

You had a tranny that had no OD..... then you changed the converter.... and now OD is there... but it shifts too early....

IMHO you have other tranny issues... and I wouldn't have put the stall converter in there without figuring out what was wrong... that kept it from OD.

Maybe someone else can be of more assistance.

I don't believe there are other issues. It was believed by the previous owner that the converter was the problem (He is a mechanic). He included the new Pro Torque converter when i purchased the car......I think it has something with the extra thickness of the tractor fluid.........don't trannys shift based on fluid pressure? I am in no way an expert but I think they work by fluid pressure, so if the fluid is thick then this would raise the pressure causing it to shift early? Yes or no?????

 

[77 cruiser]

Didn't happen to pinch the TV cable? Sounds like it's not working. Unhook it & pull it with your hand, should move easy for about 1/2 in. the get progressively harder to pull.

 

[excobraguy]

Hey guys, thanks for all of the great replies. I changed the fluid tonight back to regular Dexron/Mercron III and removed the tractor hydraulic fluid, BINGO! Problem solved. I guess the kind I bought was too thick for this transmission and was causing it to shift too soon from the extra fluid pressure? The guy I bought the car from had installed a new high performance servo and some other misc. stuff, don't know if that played a part in not being able to use the hydraulic fluid. Anyway, the car is running fine again!

 

[77 cruiser]

Good you got it. I've used 424 before & that worked OK.