Pontiac renovations, part 24.

Strip-down of the gearbox began in earnest. With the service manual in hand, I was able to determine the correct procedure to dismantle it.

Upside down

The manual states the first thing to do is to upend the gearbox and mount it in the gearbox holding jig. I don’t have a jig so it just sat upside down on my new bench instead.

A volume of dirt

First impressions upon removing the oil pan were not good. There was a lot of black gunge, which draining the fluid belied, being rather clean red when it came out.

Dirt flushed

I flushed a lot of the dirt out, which left behind a lot of metallic swarf and a few molten globules of metal. Not a good start at all. I was hoping at this point it was merely remnants of a burned up clutch plate.

Clean oil pan

I thoroughly cleaned the oil pan and leveled the gasket surface with my orbital sander.

Clean steel

I then cleaned the old paint and rust from the exterior of the oil pan. Originally the pan was zinc coated and not painted; somebody had painted it gray in the past.

Painted oil pan

The original color is battleship gray, but I opted for Solstice Blue again.

Oil filter

I removed the gauze oil filter. Somebody had added blue sealant to the rear pump pickup point. This made me cringe.


I began to follow the manual to remove the control block, reverse control and band servos.

Planetary sets and reverse

That left the core of the gearbox in place; the front and rear planetary sets and the reverse mechanism. I removed the reverse gear assembly and undid the main bearing cap holding the two planetary gear sets in.

Rear assembly removed

I removed the snap ring holding the rear assembly in place and pulled it off the fluid delivery sleeve (the section that provides hydraulic pressure to the clutches). At this point I was able to determine the source of the swarf and metal shavings in the oil pan.

Oil delivery sleeve

One oil control ring was fractured and the sleeve itself was very badly scored. The sleeve should not make contact with the drum at all where the rings are.

Overheated bearing

The bearing surface showed it had overheated and worn away significantly, allowing the drum band system to pull it off center and force contact with the oil delivery sleeve.

Main bearing

Removing the snap ring from the front assembly showed similar damage to the bearings, allowing it to be well off center and tear up the fluid delivery sleeve on this side also.

Main driving shaft

The main driving shaft (output of the primary epicyclic to the fluid coupling torus) is made of much tougher metal than the fluid delivery sleeve and has escaped much in the way of damage.

Thankfully, parts are available and I will be able to rebuild all the damaged sections. I need to take the assemblies apart and check the clutches for condition.

Leave a Reply