GMC TRANS and GARY SHARP

[rich and dottie major]

Pennzoil "10 Minute" oil change establishments have a transmission service
that completely pumps out all the old trans fluid including the torque
converter then pumps in new fluid. I had it done on my 78 Kingsley recently.
The cost is about $90. I did not have the pan dropped or the filter changed
this time because I did that about a year ago. The cost is a bit more if you
drop the pan and change the filter. The price is a bit high, but it's worth
it compared to the alternative.

Rich Major
78 Kingsley

> Does any one have info on draining the all trans fluid, not just the 4 qts
> when you pull the pan?
> Gary Sharp how much and where etc. for your 73 ? Arden

 

[marilyn & arden sniffen]

Does any one have info on draining the all trans fluid, not just the 4 qts
when you pull the pan?
Gary Sharp how much and where etc. for your 73 ? Arden

 

[scott woodworth]

Arden,

I've overhauled quite a few transmissions and here's the procedure I
used many times with great results. If you have your factory GMC
motorhome shop manual handy, you may refer to Figure 13 on Page 7-25.

Step 1: Disconnect the lower transmission cooler line off the radiator
and connect a 3/8" hose to it.

Step 2: Place the other end of the hose in a large container and have
someone start the engine while you're monitoring the fluid output. When
the fluid stops flowing, stop the engine and fill the pan.

Step 3: Start the engine again and watch for a fluid color change,
which would indicate that all the old burnt fluid has been expelled.
When the color turns red, shut the engine off and reconnect the line to
the radiator.

Note: If you wish to purge all the old fluid, then your connection
point would be the driver's side transmission cooler line at the
transmission end. If your cooler and lines are really contaminated, you
can get a aerosol can of special transmission cooler flush from any
major transmission parts jobber. The can has a plastic hose and a brass
fitting that screws to the above mentioned cooler line. It's important
to follow the directions exactly as stated on the can.

Step 4: Pour 8 quarts of transmission fluid in. I highly recommend
synthetic due to it's higher heat tolerance. Re-start the engine and
_slowly_ fill the transmission to the lower end of the cross hash marked
area on the dipstick. Total transmission fill is approximately 12
quarts with a completely dry torque converter. The torque converter
takes 2/3 of the fluid, so about 4 quarts remains in the pan.

Step 5: Warm the transmission by driving for about 15 minutes then
check the level again. Add fluid as necessary. Don't add all the way
up to the "Full" mark. Just add until the fluid reaches the middle of
the cross hash marked area. The fluid will expand as it gets hot
eventually reaching the full mark.

Note: Always check the fluid level while the engine is running. Torque
converter drain back after shutdown will produce a false high reading.

- -Scott Woodworth