How many transmissions have you broke?

[folkenheath]

Well, I spoke too soon.

I finally wounded my 4L80E, almost didn't make it home ( I was less than a mile away anyway).

Been sitting for a month. Go to drive it to a race engine shop for a meeting and to deliver an intake, and everything is fine going from my shop to the house, but when I pull out of the driveway then it shift's soft. I thought, that's weird, it does not shift soft. Then a go a mile down the road and nothing, won't go forward, backward, nothing. I flip the screen on my digital dash and I see it has almost zero pressure (I installed a 500 psi pressure gauge in the port for data logging).

Anyway, I checked the fluid and it looked fine, level was good, wasn't burnt (I just changed it last fall before a race that went fine).

Anyway, shut it off to think. Started it back up and it had partial pressure, so I backed up toward the house quick. That lasted a minute before it lost pressure again. I limped it back home in reverse after letting it sit for a minute again. Added a quart anyway just to test it, same result.

Then I unplugged the trans ECU connector to test if it was electrical, same result.

So its mechanical. So I need to pull the pan and look for something obvious like the filter came loose or something. (I've never had that happen to me)

Otherwise it may be time for a rebuild after 12 years of abuse street driving and drag racing at the track.

It's just weird, it will have pressure at startup, and then it slowly drops over about only a minute to almost zero. Like its pumping all the fluid somewhere and there isn't any left, but where is it going? I'll check the filter but there are no external leaks, and I only use a separate trans cooler.

I still drove it home, so it's only wounded thus far!

 

[Bent77]

Probably all that cheater spritz…

 

[Greg Ducato]

Sounds like the filter is clogging with whatever is doing a come apart.

 

[folkenheath]

Update...I pulled the pan and there was very minor clutch material in there, nothing that isn't normal for wear. Fluid wasn't burnt. Filter was still in the seal, looks near impossible for that to come out of a stock 4L80E pan as it wouldn't fit. No metal, no sludge, nothing out of the ordinary.

So I thought about Greg's comment above because it just made sense if the filter wasn't out of place like I was thinking. I went and got a new Wix filter and put the same fluid back in (never done that before but it looked fine and I just flushed it last fall and was worried it was a goner trans) and bam, works fine! Presssure is back to 175 psi.

Although I fear it is still wounded since that filter was apparently restricting the fluid flow. I'll see if it lasts until winter and plan to rebuild it over winter. It can only take over 1000 HP so many times anyway so its past due for a refresh. So even though the filter wasn't that dirty, it was blocking flow, strange. I would expect that with a Fram maybe, but I don't buy Fram, ever. But the filter wasn't new, I just flushed the fluid and left it in there with clean fluid anyway and low mileage.

 

[Greg Ducato]

We have seen the socks in the filter collapse and cause restriction, that may be what happened here. Hopefully you will get some more life out of your trans and spare yourself the trouble and expense of repair for a while longer.

 

[folkenheath]

I think you are right Greg.

I've seen that with Fram oil filters. Once you block the filter bypass bad filters show up immediately, and we have had brand new Frams have zero oil pressure. Swap to a Wix or Mobil 1 (or I used to use Delco) and bam, problem solved.

Seems to be the case here it just happened over time with minor wear is all.

 

[miniwally]

We have seen the socks in the filter collapse and cause restriction, that may be what happened here. Hopefully you will get some more life out of your trans and spare yourself the trouble and expense of repair for a while longer.

I have a recall on my snowmobile for exactly this, the fuel filter sock was collapsing and restricting fuel flow and thus made it throw limp mode. That's not cool on a big climb in deep snow.