700-r4 Failure

[west85]

Today When leaving the drive way I noticed a ticking noise when starting off in either drive or reverse. It kind of almost sounded like there was a buzzing noise as well. It would do this when taking off then go away and seem to be fine. I did not go far from the house so i only got into third gear, but 2nd and 3rd gear seemed to work fine. Then when turning out onto the road back to the house there was a pretty loud bang and it started slipping, and running rough. I shut the engine off, started it back up put it into gear and the engine died. I then tried it again and it doesn't bog the engine down anymore, it just won't move. When I put it in either 1st or reverse it will lerch just a little bit and then just sit and squel a little bit, I haven't done this much in fear of burning up the clutches. Any ideas? The pump maybe? Don't know why the pump would kill the engine. I have some tranny experience but am far from an expert and any help would be greatly appreciated. Thanks.

[DmaxMaverick]

If it were a 4x4, I'd say transfer case. But, since it's a C20, sounds like a broken flexplate or torque converter. It doesn't sound like a "normal" 700R4 failure at all. Pulling the tranny should tell the tale.

[Robyn]

If this is an early 700 it could have a cracked input shaft.

The 700 has many flaws that if not corrected with aftermarket upgraded HD parts can let go.

The only solution is to get the tranny out and see what happened.

Sorry to hear of the loss.

Robyn

[west85]

I just got done with a pessure test. Every gear is within the range it should be. So the pump and the valve body should be working. There is a almost kind of hissing, whirling noise with a tick that gets much faster when put into gear. Flexplate looks good. If it is just the converter that would be great but I don't know. Any ideas? I'm going to pull the tranny sometime soon but would just like to know if there are any other opions on what it could be. Thanks for the replies so far I appreciate it alot.

[DmaxMaverick]

The stalling when you put into gear is a pretty good indicator. Fairly likely the TC has failed internally. Even if the transmission has seized (everything behind the TC), the converter wouldn't allow the engine to stall. If it's stalling the engine, you've lost your fluid coupling, which is the primary function of the TC. The TCC has probably grenaded. At this point, running it any further will increase the chance of contaminating the tranny with whatever it may be puking out.

[west85]

Well,
I pulled the tranny and it was the converter that puked. When I pulled the pan there was quite a bit more metal than I would have like to have seen in it, from the converter. I was wondering were the return from the converter goes? Does it go directly into the pan past the TCC, or does it go anywere else contaminating those areas as well. I just rebuilt the tranny 20,000 ago and would like not to have to pull it all back apart, maybe just get away with a flush, but if I have to I will.
Thanks

[Robyn]

Sorry to hear of the untimely death of your little critter.

Now that its out I would seriously recommend ripping it apart and washing it out.
There are just too many valves and other devices in this box that can get fouled up with loose crap.

The entire box needs to be washed out and cleaned of all debris.
This means all the servos, the clutch drums and the valve body as well as all the passages in the case.

Be sure to flush the tranny cooler/coolers well as the last place the oil goes before it reenters the tranny is the cooler.
The passages in the coolers are finned on the inside and can habor tons of crap.

Flush the things in reverse of the way the oil normally flows.
One very important thing that MUST be done at this juncture is to add an inline spin on filter to the return line to the tranny.

Even with a good flushing there will still be a lot of crap that wont come out for some time and when it does it can still spell trouble to your tranny.

A nice little remote engine oil filter (does not need to be a huge one) will catch any crud and then during engine oil changes you can spin on a fresh filter and add a pint or so of oil to the tranny.

Auto boxes are always churning up junk even if they have not had a failure and the extra filter is a lovely addition.

The filter in the pan is to be BLUNT a clod sifter and takes out the big stuff but having a good filter on the return will drop the size of any returning particles to a much smaller level at least down into the 5 micron size.
I would not go below 5 microns and this is why I say engine oil filter.

Be sure the filter mount or filter has a bypass just in case the thing plugs up.

I would recommend changing the filter after a couple hundred miles and then every oil change therafter.

With this in place the tranny filter in the pan will have a fairly easy time of life.

Under normal operation these boxes make all sorts of very fine metal particles (the gray to black sludge in the pan) plus clutch lining and other stuff like bushing and thrust washer material.


Best of luck

Robyn

[DmaxMaverick]

The fluid from the converter is dumped into the pan. Problem is, any small particles will be picked up, and what doesn't get filtered by the "filter", gets pumped through the tranny.

The best thing to do is as Robyn suggests. While you are in there, a hardware/clutch kit is not a bad idea, and relatively cheap (since labor is already spent). And, an inline filter is a good idea, any time.

However, if disassembly is not an option, or not economically sound at the moment, a flush of the system and cooler is necessary. The valve body also needs to be dropped and cleaned. Short of that will be certain death in short order. Depending on how the failure occurred (instant or long term), and how long you drove it like this (or attempted to), you may get lucky. If it was instant, and not much driving attempts afterward, internal contamination should be minimal.