C6 Replacement?

[swampedout]

So my trans has been slipping simce I bought it. Havent flushed the whole thing yet, just kept the fluid topped off to keep it on the road until I can get time to work on it.

Someone locally is selling a c6 from a mustang, that they say bolts onto a big block. Will this bolt up with my t case or do I need a 4x4 trans?

Im doing my own research, but wanted to ask the experts.

[Gary Lewis]

It won't work.  There's a different tailshaft section for the 4wd transmissions than the 2wd's.  And from what I remember you disassemble the whole transmission to swap the tailshaft section.

[Machspeed]

swampedout wrote

So my trans has been slipping simce I bought it. Havent flushed the whole thing yet, just kept the fluid topped off to keep it on the road until I can get time to work on it.

Someone locally is selling a c6 from a mustang, that they say bolts onto a big block. Will this bolt up with my t case or do I need a 4x4 trans?

Im doing my own research, but wanted to ask the experts.

Be advised that if you flush that trans the slippage will likely be worse.

[Gsmblue]

Machspeed wrote

Be advised that if you flush that trans the slippage will likely be worse.

I have heard this from other sources but don’t understand why it is the case. Any chance you can help fill in the gap for me please?

[kramttocs]

Can't speak to if it's a valid concern or coincidental but I've always heard that since the flush sends the fluid backwards it can push pieces out of the filter and into places they don't belong. Also something about removing beneficial buildup but don't recall the specifics of that.

[86 1/2 Brutus]

All i can say is this, i've always heard this and have seen it happen.  I know on older transmissions, C4, FMX, C6, do not flush them out,  just keep adding transmission fluid.  i have no clue why other then metal filings getting into the transmission
We have to change the pan gasket on Brutus and am wondering myself if i should change the filter or not

[Gary Lewis]

"Flush" is different than "drain & refill".  I, too, have heard that you shouldn't have a transmission flushed, and I think it is probably as Scott said - due to pushing things into places they shouldn't be.

But I also know that some shops seem to confuse the two processes.  My SiL had a Jeep Cherokee that was slipping badly in reverse - so badly that it wouldn't back out of his driveway w/o racing the engine.  We proved that the problem was old fluid by adding a bottle of conditioner but, as I told him, that didn't last long as he needed all new fluid.

He tried to get it drained and refilled at two different shops and both refused to do it saying it would ruin the transmission.  When he called to ask for advice I told him to keep trying until he found one that would, but make sure it was only going to be a drain & refill.  He did find a shop that would do it and that solved the slippage.  The tranny was still going strong years later when he sold the truck.

There are all sorts of chemicals in ATF, like seal swellers and friction modifiers, and they lose their efficacy over time and with dirt and miles.  Draining and refilling with new ATF is the only way to fix that.  It may not solve a shifting problem, but it is sure a lot less expensive that a new transmission.  And I've seen it work many times.

[old55pete]

Something I learned from an older auto trans guy back in the day. The problem with these new trans flushing machines is that they do a pressurized flush at pressures higher then the trans would normaly run the trans at while driving. Not to mention that it is a reverse flush.

That being said, he told me to drain the pan, fill it with new fluid, remove the return line from the cooler to the trans, at the trans, and refill the trans with new fluid. Start the engine, IDLE ONLY, with the return line in a bucket and watch the fluid. When the fluid comes out clean or quits flowing, shut off the engine. If the fluid dident come out clean before it quit flowing, re fill the trans and do it again until it comes out clean.

Then remove the pan and change the filter and clean the pan magnets. I have been doing this for years and havent had a problem with it

[ratdude747]

My understanding is that if the seals and the like have conditioned themselves (worn) to accommodate gritty thick fluid, thinner new fluid will leak past and as a result, nothing will actuate.

That said, Lucas Stop Slip can help with such... although if the friction materials are burnt out, then no mechanic in a bottle will do anything.

[myrl883]

The biggest problem that makes this urban wive's tale seem true is that many older vehicles have been severely neglected. Many owners, when the transmission starts to malfunction, will finally service it believing that this will somehow magically fix it.

Changing the fluid when there is already a problem developing will not help a darn thing. But it will NOT make anything worse!

It's like saying "I have a cavity, maybe if I start brushing my teeth, it will go away". SHEESH!

[Machspeed]

ratdude747 wrote

My understanding is that if the seals and the like have conditioned themselves (worn) to accommodate gritty thick fluid, thinner new fluid will leak past and as a result, nothing will actuate.

That said, Lucas Stop Slip can help with such... although if the friction materials are burnt out, then no mechanic in a bottle will do anything.

This is my understanding as well and I have experienced it. A flush or even a fluid change in an already slipping transmission removes the free floating friction particles in the fluid making the situation worse. And, the Lucas Stop Slip, while a band-aide, is pretty good stuff....lol!