I just put my new (rebuilt) 351W into the Bronco, hooked everything up and the transmission is slipping. Pan was leaking so I changed the gasket and filter, put 4 1/2 quarts of mercon into it, did the 2 minute idle shift through the gears and checked it and the level was good. Drove it maybe 2 miles and it was slipping bad, got it back on level ground and check the fluid. Not even on the dipstick, so I add another quart and drive it another mile. Still slipping, check it and add another quart or quart and a half and same problem. It's a C-6 and it worked great less than a month ago when I pulled the motor. It leaked the whole time it was on the jacks till I changed the gasket yesterday. Any ideas why it would be doing this all of a sudden? It honestly feels like it doesn't have enough fluid but I've added quite a bit. I'm pretty frustrated right now. Any help is greatly appreciated! I want to drive this thing!!!!--Eric

 

Sometimes when you change the fluid it can cause some nastiness’ knocking build up loose and what not. Is the fluid level good now? If not keep adding till it is. If it still slips try getting a bottle of lucas transmission fix, that did it for my friends Toyota.

 

fill it up until it shows on the dipstick!

 

when you removed the engine and trans did the torque converter some how get drained? if so it will take about 13 quarts of trans fluid to fill the converter and trans.you also need to check yout radiator to make sure that there are no internal leaks in thre trans cooler which is built into the radiater.my guess is that the torque converter got drained and just needs to be refilled. when you drive it pumps the fluid into the converter. as pops 91710 says refill until it shows on the stick and stays at the proper level.try not to drive until it is full or you will be putting a trans in it also

 

That's interesting. I didn't realize the torque converter could drain out other than through the torque converter drain plug. I guess that does make sense though. The whole trans was propped up at somewhat of an angle while it was on blocks during the engine swap. Honestly I don't know what the dipstick is showing as of my last addition. Along with this problem it was overheating so I shut it down. I think the overheating was just air in the system as I failed to purge it before I test drove it. So just out of curiousity, on average how much fluid is normally added after a gasket/filter change? Or is it just entirely dependant on that particular trans and when the dipstick shows the proper level? thanks for the help, I'll be sure to check the dipstick after refilling my coolant now that I have some daylight to work with. This all happened last night after Midnight. --Eric

 

i would say that on average filter and gasket change would be about 3 quarts. of course this will vary by transmission type but that is an average.

 

If the torque converter neck pulled out from the front seal on the trans, it surely could have drained out. Not only that, as long as the front pump isn't turning (which it can't do out of the vehicle) and if the trans is sitting tail low, the oil can drain from the converter directly into the trans. and the oil in the back of the trans can pour out past the rear seal when there's no driveshaft on the output spline.

 

hmmmm, come to think of it, when I drained the trans doing the gasket/filter change it did seem as if I got alot more than 3 or 4 quarts out of it. Sure hope that is what my problem is. Probably closer to 3 or 4 gallons thinking back.....

 

Well, messing with it for just a little bit yesterday the level seems right on the dipstick but the problem is still there. What would the symptoms be if the torque converter had pulled off the front pump? Or is it possible that the torque converter is low and not being refilled properly? The only thing I can think of at this point is to drain the entire system, torque converter also, and just refill it with the proper amount. I guess there is no way to fill the converter itself, just drain it at the plug. Maybe if I can get all the fluid out and put in the proper amount, something like 13.5 quarts according to my Hanes manual, I can at least eliminate the fluid level as the culprit. Any other ideas? I really don't want to have to pay a shop to fix this. The transmission shops around here are notorious for being crooks, and I'm already over budget on this project. My wife's ready to kill me! thanks, --Eric

 

Eric, Give us a little more detail on what you mean by slipping. Is it slipping as you pull away from a stop, or is it slipping as it changes from first to second and second to third, or slipping in all gears, or slipping after it gets into third at a staedy speed.

How long does it take for it to actually drop into gear as you move it from park to rev or fwd?

Is it chattering? Or is the engine revving betwen shifts?

If you are between the dots on the tranny dipstick you are okay on fluid level. Are you checking the fluid level on a level driveway?

How does it shift when you use the shift lever manually thru 1,2,D instead of letting it shift itself in just D ?

Your front pump has to be working or you couldn't move at all.

Did you drop out the valve body for any reason?

Check your vacuum modulator and make sure the hose is on tight and not cracked and that it's hooked somewhere to a vacuum source on the manifold. Check the modulaor to make sure it wasn't damaged while moving the trans and engine around. A bad vacuum modulator can cause these symptoms too. Make sure you have no vacuum leaks on that modulator's hose.

Theres still more to go over, but this should keep you busy for now.

That C-6 is an awesome tranny. I'd hate to see it get ruined. Rebuilding them is really a piece of cake and not expensive at all, but that's not the diagnosis yet.

 

By slipping, I mean when I push the accelerator the engine revs but not much happens in the form of movement. I had a hard time getting up to 30mph. It does it in all the gears, none of them being worse than the others, and that's including reverse. I didn't actually try manually shifting from 1 to 2 to D. I will try that as soon as I can though. When I put it into gear it seems to go in right away. no delay at all. I've been checking the level in the garage where I did the engine change and everything else so it is definitely level. I know what a great reputation the C-6 has and since it worked perfectly before the engine change I can't believe it just happened to go bad sitting there. I am certain there is something stupid or obvious I have either done or overlooked. I think the vacuum modulator is a real good idea. I will check that out as soon as I can. Also, I wonder if my timing is far enough off if that could have an effect since the wrong timing could affect the amount of vacuum produced. Well, I will hopefully figure this out with all the good input I've gotten here. I've got waaaay too much time and $$$ invested to give up now! Thanks! --Eric

 

As an update to help anyone with this same problem in the future, it turned out to be my ignition timing. Somehow, I don't know how, but somehow putting the engine together and installing it the timing wound up being 10 degees AFTER top dead center, rather than 10 degrees BEFORE TDC. So now you know. Apparently the timing screwed up the vacuum so the modulator on the tranny wasn't able to do it's job, or something to that affect. Regardless, it works now, and runs oh so much cooler. Kind of surprising the dang thing even ran. Anyway, thanks to all for the input!