Hello everyone! I've had my 4L80e in my 99 RCSB now for about a year. I bought a used trans off of CL, added a Transgo HD2 shift kit and installed it with a Circle D converter. It's been working flawlessly and hasn't skipped a beat. It has never showed any signs of slip whatsoever.

The past two mornings or so, I've noticed a strange noise. It sounded like a idler pulley on it's way out. I popped the hood and listened more closely and it sounded like the alternator. As soon as the truck ran for a minute or so, the noise would go away. No big deal.

Well it happened again the next morning and sounded like it was coming from the trans this time. I popped the hood and checked the fluid and it looked slightly low so I added a quart. I drove to work and as I got close to work the noise came back. As I pulled into my parking lot, I romped on it a bit and the revs went up but without any wheel spin or acceleration (it was snowy). I thought UTOH to myself and went into work.

When I went to leave for the day, the truck seemed fine for about a half a mile and then I had pretty much no movement. I limped it back to work and now it will not really move in any gear. Just feels like it "slips'. If I let the truck sit for ten minutes and start it back up, it will briefly move forward or backward but then refuses to move again and just slips.

Now I have never once had a slippage problem. The truck is 4wd and has gone 11.6 in the 1/4 with zero issues. Two days ago it shifted perfectly under full throttle and part throttle, in both 2wd and 4wd.

It seems to me that I have just suddenly lost the pump. I don't know why the pump would suddenly die, but that's what my gut is telling me.

Any thoughts? If this is the pump, what actually "goes bad" on it?

I've rebuilt auto trannys before so I am not afraid of tearing into it. I've just never had a pump problem before and it seems like that's what this is.

I am all ears for any suggestions or ideas.

Thanks!
Adam

 

Possibly the gears or the gears wore into the pump cover. Could be a clogged filter as well, but if it is, it needs to be rebuilt anyway.
It could also be a stuck pressure regulator valve.

 

Thanks for the reply!

Is the pressure regulator valve in the valve body?

Do you sell a pump rebuild kit? Or would the frictions and everything have to be replaced at this point if the pump died or filter clogged?

 

Any more ideas?

 

There isn't really a pump rebuild kit, it usually requires pump replacement if damaged.

You'll have to get it apart to see what is damaged and what needs replacement. A failed pump usually means failed clutches as well.