1995 Aurora Classic transmission problem and solution...

[turbokinetic]

Hey all. I have posted a few threads here about my dad's 1995 Aurora Classic.

Dad bought this car with about 80,000 miles on it. Now got about 200,000 miles. There have been a few small issues with the transmission over the years. Early in our ownership of the car, the shift solenoids broke. Literally, they broke off and fell in the bottom of the trans pan! The transmission stayed in 2nd or 3rd gear (can't remember which) and the Check Engine light came on.

We took it to the local GM place, and they were happy to read the codes. The tech cheerfully told dad his car has a "blown tranny code" and they would be kind enough to install a new transmission for fifty bajillion dollars and ninety-five cents, if we left the car with them for at least a month. (exaggeration but not by much!)

I did some on line research and found out there was an updated solenoid kit. This fixed the transmission for about $75 including transmission oil.

Fast forward to about 150,000 miles. The car started to shift hard, and had a code for Input Speed Sensor. This requires removal of the powertrain to access it, so I made a software modification to bypass this part.

Finally, at 200,000 miles, the transmission developed a problem which requires removal. One day dad called me to explain that the transmission would go to Neutral if the engine speed was low. In other words, you had to revv the engine, before the trans would engage, and as long as you kept the RPM's up, it stayed in gear. But let it go to low idle, and it would fade to Neutral.

The problem turned out to be a stuck-open pressure regulator. There is a chip of aluminum caught in the regulator. It looks like the chip came from the pump casting, because there is no damage to the pump rotors and the aluminum chip is not crushed as if it went through the pump. Lucky break I guess.

So I am going to chronicle the repairs here on the ACNA forum for your enjoyment!

Here's the car, last year, fresh from the painter's shop:


And as they say, you don't remove the engine from an Aurora.. you remove the Aurora from the engine:


The cause of the transmission operational problem. See the small chunk of metal caught in the valve?:

[wfooshee]

I got pictures. I guess you fixed the post?

My Big Question is where did that come from??!??!?!? You said maybe pump casting, but unless you find a void that it fits into, you're guessing. Were it mine I'd really want better info than that!

[turbokinetic]

Jun 17, 2015 15:43:05 GMT -6 wfooshee said:

I got pictures. I guess you fixed the post?

My Big Question is where did that come from??!??!?!? You said maybe pump casting, but unless you find a void that it fits into, you're guessing. Were it mine I'd really want better info than that!

You are correct. I am going to tear the entire transmission down and inspect it, because it is 20 years old. I wanted to find a cause for this problem as early in the process as possible, so I took the pump off before separating the engine and trans.

I'm pretty sure I found the place on the casting where it came from. Looks like there is a place on there where a large check-ball can hit the aluminum and it has chipped away some of the casting. There are only a few placed it could come from, because of its position. It couldn't have come from BEFORE the pump, because if it went through the pump rotor, it would be crushed. The pump only pushes oil one way, so it can't have come BACK from the remainder of the valvebody. There are several other "shaggy" casting points on the pump, too.

I just got the subframe washed up and it's out drying in the sun. Got the engine and trans separated and about to wash the transmission. Got to find some plugs to put in the axle ports, first. It is very important to spotlessly clean the exterior of the transmission before tearing it down. It's much harder to get dirt and grit out of the parts, than it is to keep it clean in the first place.

As for the pictures, I tried to upload them to the forum, but it didn't work. Instead, I put them on Photobucket and then edited the post and put the Photobucket IMG codes there.

[turbokinetic]

Ok got a few more pictures to share!

The subframe was kind of grimy, so I started by washing it. I used a caustic water-based degreaser called Zep Industrial Purple Degreaser. Spray it on full-strength and then pressure-wash it off.


After washing:


Then the transmission goes on a dolly to roll out to the wash area:


All sprayed down with soap. Foaming nicely....


Now for a little pressure wash action! To quote a friend "I don't wash it until it's CLEAN; I wash it until it's HOT!"




So after that dries off a little, I'll start the teardown and inspection of the parts inside.

I have a spare 4T80E transmission that I bought for a project. I don't want to tear it down unless I have to because I want to build it for the project. I can't use it in the Aurora as-is because it came from a Cadillac and the final drive ratio is not the same. But, if worse comes to worst, I can use it for parts and buy another core for my hotrod project later.

I've built plenty of 440T4 / 4T65E variants but this will be my first 4T80E build. If I run into any specialty tool needs, I will fabricate what I can. With the factory manual, and the ATSG manuals, I am sure the information is here.

[turbokinetic]

And I got the transmission mechanical parts torn down! There were only a few problems. It was definitely time for a rebuild - but the transmission would still have functioned with only clearing the stuck valve.

First the final drive cover comes off.


Then the final drive and ring gear come out. I mark the OUTside of each snap ring so that there isn't any question later. It often does not matter, but sometimes it does and I don't want to take a chance.


Now the other end. The cover off. You can see the horribly located input speed sensor there in the center!


Chain assembly out.


No Chinese bearings here.


Now the parking lock comes out:


Now all the guts are out of the case!


So for the damage? Here is the first area. This is the 4th gear band. It must grip the drum and hold it stationary to make 4th gear work. With the stuck valve, the engine speed was too low in 4th and the transmission would cycle in and out of 4th gear. The band and drum got hot. The drum I can polish, but the charred band will require replacement.


These clutch plates look perfect.


These also look perfect.


This clutch is the Forward clutch, necessary for all forward motion. The clutch doesn't appear burned but the friction lining has severe fatigue and one plate is almost totally worn out. I can scratch it off with my fingernail.


Next, the clutch piston seals need to be changed. They are in the clutch baskets, under the return springs. The spring retainer has to be mashed down to get this out. There are special tools for this, but I have been using homemade and makeshift tools because I am just that kind of guy. LOL.


The seal is fine, but it's 20 years old. This is a common failure point on all auto trannys. If this gets hard and shrunken, the clutch won't apply firmly. It will slip and burn out.


Had to use a modified gear puller to compress this one....


Some more gears out.


So, it looks like there isn't any severe mechanical carnage. I didn't expect any severe damage because of the failure symptom. Dad is a mechanical engineer and he stopped driving the car as soon as this problem appeared.

[RCA1186]

Wow great pictures and read, thanks for sharing it with us!

[turbokinetic]

Hi guys! I have been busy with other things for a few days. Also had to wait on a few parts for the Aurora trans job. But now the transmission is fully re-assembled and ready to go back in the car! I have taken a load more pictures and will post them here.

I like to take many pictures during any major repair like this. It helps when putting it back together. The ATSG manual shows 99% of the critical steps of the build, but there are some things that are not easy to tell from the printed manual. The teardown pictures tell the story. One such thing is the position of "special" external fasteners. The transmission housing bolts are mostly "plain" but there are a few with stud heads that mount external parts such as the shifter cable, wiring harness etc. Those need to go in the same position so that the parts will all mount back in their correct places. The manual often doesn't show the stud positions.

New clutch friction discs get soaked with oil before installation. They work by surface oil fluid film (surface tension) and if they are dry they will not grip.


New pressure control solenoid and torque converter clutch solenoid ready to go in the valve body.


The new pressure control valve (force motor). Notice the blue paint spot, with the center screw turned IN about 1/8 turn? This increases the pressure developed per any given current signal. This will help the transmission to have better torque capacity under heavy loads. During light-throttle use, the ECM will adapt for this and it won't cause harsh shifting.


Pump rotors all clean and going back in the pump housing.


More valvebody parts, clean and looking ready for another 200,000 miles!


New clutch piston going in. This is called a "bonded piston" or "bonded seal piston." It doesn't have a removable seal like the older transmissions. This makes for a longer-lasting transmission before the first rebuild. The problem is these pistons are expensive. Some shops may skimp and re-use the old ones. I did not re-use them because the old ones have 20 years old rubber in them and they are harder than the new ones.


NOTE I have more pictures but having upload difficulties at the moment. Will post more later.
Thanks,
David

[turbokinetic]

So yesterday and today I have been a little bit distracted! A friend of mine gave me an early birthday gift. It is a 1980 Oldsmobile Cutlass Supreme Coupe. Complete, unbastardized, and 100% original including paint. It has the Buick 3.8 carburetor V6 engine. I spent some time repairing the air conditioner and that took me away from the Aurora project.







Here are some videos of the Cutlass:

The car:


The A/C rebuild:


So, now back to the Aurora transmission repair! As said, the transmission is fully assembled and ready to go back in the car. Here are the rest of the pictures of the subassemblies going back together.

Another bonded seal piston - the old and the new:


This is a "standard" piston with removable seals. I have put in the new seals with TransJel to lube and help them slide in the bore.


Next the return spring goes in:


And the clutch plates, pressure plate, and snap ring!


The pump completely assembled - both the primary and secondary charge pumps, and the scavenge pump.


Lower valvebody all together. Note the Shift A and Shift B solenoids on it.


Ready for the lower valvebody assembly to go in the transmission..


Lower VB installed and pan going on....


Upper valvebody and pump installed. Putting the side cover in place....


Now ready for the final drive to go in the housing....


Final drive in and cover going on....


New Transtar GM84 torque converter in. All external parts on.


So that's a rebuilt 4T80E transmission ready to be mated to the 4.0 V8 engine and put back on the subframe! I hope to make progress on it tomorrow!
Sincerely,
David

[turbokinetic]

Ok! For today's update, I have the powertrain back in the car!

First I turned my attention to the subframe. I don't know if I blasted away the reflective foil with the pressure wash, or if it was damaged already. But, the steering gear heat blanket needs attention. The exhaust is RIGHT above this and it's going to get too hot.


The roll of thermal tape sitting next to the blanket with the foil removed.


Thermal blanket with new foil tape covering:


refurbished blanket installed over the steering gear:


Now for the powertrain install to the subframe! The engine and trans assembly are installed to the subframe. Note that there are only 2 mounts and they are on the transmission end. The green strap is holding up the other end of the frame. Otherwise it would "droop" down and put a horrible bind on the 2 mounts. There is a special tool that holds the engine and frame together but I don't have it.


Now for the scary part. Got a logging chain connected to the car's frame and about to hoist the car body up.


The Aurora is High and Exalted!:


The engine can now be rolled under it with the furniture dollies.


And the car lowered....


And now the hoist connected to the engine its self, to "suck" the engine / trans / subframe assembly up to the body.


And the subframe has firmly contacted the body!


And she's in! That's my stopping point for the day. Powertrain and subframe in the car. Steering column connected and subframe bolts in.


Hope to get all the things hooked up and connected tomorrow.

I hope this is interesting people here. If I get comments I will post more like this otherwise if it is boring or off-topic I won't. I hope this shows you that you can do these kind of jobs with basic mechanics tools and don't have to have a mint of money worth of specialty stuff to get the job done.

Sincerely,
David

[turbokinetic]

Alright! Finally got her back on the road! The only problem is, the exhaust pipe is broken. Someone had made a crappy repair to the pipe, and I guess I caught it up on the engine while hoisting the car body off the subframe. The pipe got bent down at a 45° angle, and then it cracked when I bent it back up.

So today the car was dropped off at a muffler shop and hope to get it back tomorrow.

Here's a test-drive video:
www.youtube.com/watch?v=sGsS-aN1LJI


Once again, I hope this has interested some of you.

Sincerely,
David

[tigger]

Nice work!

...om both the trans and this thread, haha!

[turbokinetic]

Jun 30, 2015 13:59:19 GMT -6 tigger said:

Nice work!

...om both the trans and this thread, haha!

Thanks!

[chokung]

Wow, Great work!!

I have a question on how you do the software modification? I got the classic 95 as well, now has about 137k and start to shift hard some time; oddly I scan with Acton CP9145, only code 84 popping up and if I clear the code, car shift normal again!


"Fast forward to about 150,000 miles. The car started to shift hard, and had a code for Input Speed Sensor. This requires removal of the powertrain to access it, so I made a software modification to bypass this part."