Hot Rod Cadillac Adventure

Figured it was time to have a build on the Caddy, since it is turning out to be an adventure of sorts. First, the vehicle in question:

Purchased from Poopshovel, here it is at his home, and then at mine.

I love that car.  To bad my cheapness prevented me from buying it.

Put on the engine covers to see how it looked. It does look better, but of course the LS engine isn't much of a looker stock.

While giving it a bath, I did notice something odd about the rear wheels.

Drivers side, sedan wheel, 19x9.5, 56 offset

Passengers side, coupe wheel, 19x10. 40 offset

Coupes had different rear wheels than sedans. The coupe wheel fits okay, just a bit close to the edge of the quarter. So I will either find a sedan or coupe wheel if I can, prices on them aren't cheap, at least GRM cheap that is. 

Stampie (FS) said:

I love that car.  To bad my cheapness prevented me from buying it.

Wait till I post some more, your cheapness might be a blessing.

Since the car had the slip/flair going into 3rd, I decided to do a trans service, to see if that helps. Not too bad to do, other than refilling it taking a bit longer since GM didn't put a dipstick on it.

Inside the pan, where all the vodoo happens.

That did help it some, shifts were better, but the 3rd gear slip/flair was still there. I did take it to an Atlanta region autox, did okay for my first time in this car, better once I figured out how to correctly put it into manual shift mode. Round trip was just over 250 miles, so it performed well.

Now that autox was on a Sunday. I didn't drive the car again until that Thursday. Well, tried to drive it. Caddy wouldn't back up the driveway, it would just stop, bringing the rpms up did nothing. It would move on flat ground and probably would go up the driveway forward, but I decided not to push my luck. I knew the car might need a transmission when I bought it, just hoped it would last a bit longer than this. Oh well, rolled the dice, got snake eyes. Now on to the fun part.

First, had to get a tool for the job. Note: if you have a 4 post lift, get a 2-stage trans jack, this one didn't drop low enough to get under the lift with the transmission on it. 6L90 is a big beast.

So what do you do when this happens, you improvise. Used the engine hoist to get trans off the jack, then onto a rolling tool box of course.

So now that it is out, its time to make a mess, literally. No matter how much you try and drain an AT, there is always fluid hiding somewhere. Pulled the pan and there was quite a bit of crap in it considering it only had 400 miles since the service.

Here is the valve body and TCM (the brown part). Yep GM put the trans computer inside the pan. Thank you engineers.

Here it is with the valve body and TCM removed.

Took the pump/bellhousing off, the pump is made into the bellhousing. Pump was in great shape. Turns out the transmission had been rebuilt before, they had used the good red clutches in it. Torque convertor felt like it had more stall than stock, but no ID on it to tell what it was.

Pump/bellhousing

Here are some of the drums, including the problem one.

Here is the offending part. You can kinda see the crack on the inboard part of the weld, easy to see in person. Here is a video showing the problem, the part where he test 3-5-R.  Video

Now I get to order parts for it, plus get the special snap ring pliers to get the intermediate support snap ring off. Tried my luck with screwdrivers and pliers, decided it was a better idea to get the right tool. Big old snap ring around the inside of the case, you can sort of see it in this picture, ends of the ring are near 10 and 12 o'clock. More to come as I go through the rebuild.

In reply to 81cpcamaro :

This is fascinating, thanks for sharing the rebuild process!

In reply to Pete Gossett (Forum Supporter) :

You're welcome. Figured as I am learning about doing this, it might help someone else out. 6L80s are the same (few minor differences) and there are a lot of them out there. 

Plus it was one of the last things I haven't done myself on a car, done a few manual trans, so just time to add this to the list of things. Not sure I would want to do it for a living though.

In reply to 81cpcamaro :

I changed an AT filter on the 700r4 in the Vette and that was terrifying enough for me. I think I'd rather take up voodoo as a pastime than dig into another automatic transmission. 

I wondered where this went ......will definitely be following this.....have stories of my own on my 2010 'V'  6spd.......and  I have the original rims up in the grosh attic ...just sayin'

Interesting thread!  I have cars with both the 6l80 and the '90.  Generally, they work great, and they are big, fat, heavy pigs.  In case you find too much trouble in this endeavor, the 2WD truck/SUV versions can be had pretty cheaply used (and they use slip yokes).  That said, the aftermarket/hotrod world is finally addressing these things, so maybe not for long . . .

In reply to 759NRNG (Forum Partidario) :

Hmm, black, silver or polished? I might be interested.

To rustomatic, easy enough to fix this one, putting an 80 behind a LSA might just find its weakness real quick. No slip yoke on the Caddy though, IRS setup.

I think the torque input limits on both the '80 and the '90 are about the same; they should take up to 650 lbs-ish, with reasonable driving.  One obviously just has some heavier parts/case, shaft size, namely the output shaft on the 6L90.  A bummer about the '90 is the lack of a slimmer pan.

The slip yokes work great for installing in IRS setups; both of mine are IRS.  They make it a ton easier to change the rear seal, if needed (haven't done it) . . .

81cpcamaro said:

In reply to 759NRNG (Forum Partidario) :

Hmm, black, silver or polished? I might be interested.

To rustomatic, easy enough to fix this one, putting an 80 behind a LSA might just find its weakness real quick. No slip yoke on the Caddy though, IRS setup.

sent you a PM (rims)

In reply to rustomatic :

Easy enough to fix this transmission, no need to find another. Getting the rear yoke off was quite easy on this trans, it isn't pressed on, just remove center bolt and tap off.

In reply to 759NRNG (Forum Partidario) :

Got it.

Decided to pull some of the clutches out of the bad drum to see how bad they were. They were BAD, really bad. The friction disc on the bottom of pict is bowl shaped, warped as can be. They will make some great garage wall art for sure.

Tonight I pulled the clutches for the back section of that same drum, completely different look. This is how the clutch frictions should look.

Here are the clutches out of the drum.

I also wondered where this car went, and am also fascinated by the inner workings of this car's transmission. You are a brave man for tackling this. Will definitely be following. 

Thanks for posting the detailed pics!  One might assume the culprit is excessive heat, as that seems to be the main offense in auto destruction.  You have any guesses as to what else may have contributed?  Too much tap shift action?

On that note, I'd definitely add an external cooler (or a bigger/better one if the factory already did) while you're at it . . .

Great car. Saw it when it was for sale. 

Question, since you are saying this will be the cars SECOND trans rebuild! How many miles does this thing have? Are these glass trannys like Honda V6 ones from back in the day?

Car has 163K on it. It has been rebuild before, not sure if just once or more. 

To rustomatic: Problem is caused by the drum leaking at a weld, causing a pressure loss on the 3-5-R circuit (which caused heat in that clutch pack), there is a video link several post up between the picture of the drums/hubs and a close up of the bad drum. That shows the problem. If it was just heat, all of the clutches would be showing signs of that.