Slow shifting auto

Now that I've been able to drive the car a little, I remembered the trans issue. At very light throttle acceleration, the trans shifts very slowly and the engine races a little in between shifts. If you accelerate at moderate throttle, shifts normally. Trans is an 80's C-4

I noticed the trans fluid is filthy, so I'll be getting that flushed. Think that's it or could it be something else?

Thanks!

Sounds like the trans filter is clogged and shifting valve bodies are dirty - so flushing it and a new filter should do the trick. Good luck

I only ask this for my own clarification only... I have always been told not to flush a transmission as it will loosen up more of the sludge/dirt and can lead to more issues then just changing the filter and fluid?? kind of made sense to me but in the same breathe it didnt, so just asking out of sheer curiousity...

It depends on what you flush it with - just adding new fluid will flush it to a point, but if the fluid is brown and has a burnt smell to it - it maybe more than just old fluid - It would be just like changing the oil - it's going to flush a little sludge from the system, but unlike a engine, if the trans has a lot of sludge in it - it has more problems than just old fluid and it maybe material from a clutch pack or ? The trans is one of the most neglected pieces of equipment on a vehicle.

Thanks! The fluid doesn't smell burned, just dirty. More brown than red. I'll try to get that flushed soon, see if that works. Certainly can't hurt!

Well I changed the fluid and filter, no difference. Probably has a little something to do with the broken peices plastic of plastic I found in the pan

It looks like it was some sort of gear sleeve - smooth on the outside but gear teeth on the inside. Hard black plastic. Any idea what that was?

Either way this trans is probably on its last legs. Tons of sludge in the pan, probably never changed.

Either way this trans is probably on its last legs.

I'm thinking what you're thinking

Modulator valve

You said its shifting slow. Dose it hold way too long in a all gears before shifting? You didnt mention it slipping. Before you take it out, try adjusting the modulator valve on the back of the trans. Check the vac hose to it make sure it tight. The modulator valve tells the the trans when to shift, I think its set at 1.5 turns out from tight. You will need an allen to stick inside to adjust. I think thats the problem. Buy a new one for about $9.00.

Well the 1st to 2nd shift snaps off like normal. The 2nd to 3rd shift happens at the right rpm, it just takes forever for the actual shift to occur. I guess it's slipping during that time b/c the engine races a little. If I let off the gas it will shift alot faster.

I'm really wondering if I actually have a 4-spd C-5 thats just really screwed up and not going into 4th at all. The 3rd gear rpms seem really high, esp given the town car rear end. I also could never find any "C-4" marks on the trans to identify it. It's def not a C-6 b/c I have one of those and its quite a bit bigger.

I think I finally found something which confirms it - it's a C-5, basically a c-4 with a lockup torque converter (which isn't working). Probably explains the broken plastic gear in the pan.

64-83 (now designated "C4" by Ford)
Case fill {C4 to C9, D0 to D9, & E1SP)
Pan fill {C5 to C9, D0 to D9}

82-86 (now designated "C5" by Ford)
Case fill {E2AP only)
Pan fill {E2TP only}

Finally got around to messing with the modulator - got it shifting much better. Now its basically fine, certainly good enough that I'm not going to replace it.