C6 Problems--Advice Needed

[Diogenes]

Tonight was a beautiful night here in NW Ohio, so some country road cruising was in order. Unfortunately, I barely got the Galaxie home. I slowed for somone making a turn, downshifting into 2nd and then got into the throttle once I was able. It accelerated as usual and I upshifted into drive--it free revved a bit and then was fine. it did it again but then stayed in drive. I went straight home. It felt like there was some mild vibration, but I chalked it up to the road. I turned down my road and it didn't want to go into drive, but manual shifting got it there. Went to put in garage but had to back it up to line up, but it was done. Checked fluid, looks good but may have been a bit low, added some fluid, started engine and tried getting into gear--nothing. No forward or reverse, thought I may have heard a little "sheet metal" like sound, very little. Now, with car in park if I start engine there is a vibration.

Any thoughts would be greatly appreciated.

[fryedaddy]

it may be something as simple as a modulator valve or line to modulator valve stopped up.unhook at both ends and blow through it,it may just be clogged.i have to blow mine out every now and then or it wont go into drive,but yours wont move at all so i dont know.

[e philpott]

Sounds like your torque converter is coming apart and would explain the “ won’t move “ yet fluid still looks good along with the vibration.

[Diogenes]

I've had mine accidentally disconnected in the past, it just wouldn't upshift into drive. I did as you suggested anyways, since it is simple to do-no change. When I rev engine I hear something, but hard to describe. Its faint, and a vibration. Friend thinks it may be convertor related.

Jegs has a TCI street rodder transmission package for just shy of 1500.

[Diogenes]

Sounds like your torque converter is coming apart and would explain the “ won’t move “ yet fluid still looks good along with the vibration.

I was responding while you posted--my friend agrees. If that is the case, how would one determine that to indeed be the case? Does it trash the whole trans? I'm an automatic trans ignoramus, unfortunately. Toploaders always seemed more simple--and fun.

[e philpott]

Just install a new stock converter for around 120.00 dollars.

Vacuum Modulator controls pump pressure which has a direct effect on light throttle cruise shift points like you found out , full throttle romp through the gears you would never know the vacuum line was off

[e philpott]

If the fluid in the pan is good just change out the converter and go

[Diogenes]

Just install a new stock converter for around 120.00 dollars.

When I pull the converter, will there be obvious sign of failure? I'd hate to put it all back together for nothing.

[e philpott]

Nope, it probably has a bad spragg in the stator freewheeling both directions instead of holding one direction

[Diogenes]

Thanks for the info. I guess I gotta tear into it. At least its about the end of driving season in this neck of the woods.

[67xr7cat]

I'd start by adding a quart or two of fluid.  It may be low and dipstick is off.  Next step be check for line pressure. Stuck pressure regulator, pump problem be no or low line pressure . If line pressure is good then be a converter or input shaft broke. 

[Diogenes]

I'd start by adding a quart or two of fluid.  It may be low and dipstick is off.  Next step be check for line pressure. Stuck pressure regulator, pump problem be no or low line pressure . If line pressure is good then be a converter or input shaft broke.

I did add a quart, thinking it was a little low, but no change. What is the best way to test line pressure? I'm not familiar with anything beyond filter, fluid, and linkage on an AT. I guess its time to educate myself.

Thank you for the information!

[Lowrider]

Possible that the input shaft spline stripped out. Either the spline in the convertor, forward clutch or the shaft itself. Had that happen to me on a C4 years ago. Bad thing is it sends metal debris throughout the trans. I "only" needed a convertor but had to disassemble & clean the whole trans because of the metal in it.

[gt350hr]

  Reverse has very high line pressure and will engage when forward gears won't. In your case  ( as others have already said) since you have nothing , the input shaft isn't turning the planetary it is hooked to. It certainly could be the splines ripped out. The convertor sprag could break , but they usually "lock" , not freewheel. Once ( in a C4) my convertor broke the pump fin section away from the rear cover. That meant the outer shell was only turning the trans pump , nothing else! My convertor guy ( Munsinger) had never seen this happen.. My bet is the planetary splines.
   Randy

[cjshaker]

I used to rebuild automatics about 35 years ago, and I've forgotten 95% of what I used to know, but I've seen pumps go bad on several occasions. Symptoms are very similar to what was stated here. I don't know if that's the issue, but just shows that there are quite a few things that can give similar symptoms. One reason why I hate autos.