| Transmission Fluid Unknown Age [message #352760] |
Sat, 14 March 2020 18:22  |
Melbo
Messages: 144
Registered: August 2018
Location: Albuquerque NM
Karma: 0
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The GMC was started for the first time today since I bought it. It has new timing chain and gears new water pump new fan clutch new fan new fan shroud all new fuel lines new fuel filters electric fuel pump and the starter alternator and radiator have been gone through. New belts and hoses. I changed the oil and pulled the dizzy and ran the pump. New antifreeze. New power steering pump and new belts. I have some more new parts to install but I was at a point where I could see if it was going to run and it fired right up and runs nice and smooth. I am wondering if moving it (this is my first opportunity to do so it was towed in and parked) with the old transmission fluid is a good idea or if I should change it as well before putting it in gear. Any opinions would be greatly appreciated.
Thanks
Melbo
Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
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| Re: Transmission Fluid Unknown Age [message #352763 is a reply to message #352760] |
Sat, 14 March 2020 18:49  |
Melbo
Messages: 144
Registered: August 2018
Location: Albuquerque NM
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Thanks Emery
I already did the headlight oil with the motor oil and the p/s fluid with the p/s pump (and conversion to electric wipers). So I will dive in tomorrow and get the last two (trans and final drive) done. The brakes are on the list along with some brake lines that look like they need to go but not before I get a chance to move this so it is a little more accessible.
Thank You
Melbo
Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
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| Re: Transmission Fluid Unknown Age [message #352767 is a reply to message #352760] |
Sat, 14 March 2020 20:51 |
Melbo
Messages: 144
Registered: August 2018
Location: Albuquerque NM
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I was checking the maintenance manuals. I'm guessing 90 wt for the final drive and Dexron for the trans. Any advice on this (I know I'm opening a can of worms but a sense of direction is helpful) would be greatly appreciated.
TIA
Melbo
Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
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| Re: Transmission Fluid Unknown Age [message #352768 is a reply to message #352760] |
Sat, 14 March 2020 20:52 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Melbo,
I've published this several times but not int he last several years, so...her goes again for the newbie'e and others that have not seen it.
You can take it to a "Jiffy Lube" type place to have them change the fluid, and to my way of thinking that is the only way to
*completely* change all of the fluid, as long as you have the filter changed also. The only catch is, the last couple of times I
stopped at a "Jiffy Lube" type place, they were *not* offering synthetic fluids as a change option. So you may have to make a sort
of deal with the owner/manager to use synthetic fluid. That being said, you can get most of the oil out using the following
procedure. Keep in mind, there are several...perhaps many... that would not do this (including IIRC Manny). I've done it many
times with no ill results. Sooooooo.....
This is a very messy procedure...you're gonna spill fluid, so be prepared with Oil dry, rags and the like to clean-up afterwards.
1. Do this with the trans cold. Wait at least over night.
2. Raise the coach high enough to get a 5 gal pail under it with room to spare.
3. Disconnect both trans lines at the radiator, and be prepared to catch the fluid coming out of the cooler in the radiator.
4. Attach hose extensions to the lines and drop the lines into the 5 gal pail.
5. Using two people, start the motor for only couple of seconds. Do this to identify which line the fluid will come out of. Now
you know which line you *must* keep in the bucket.
6. Again, using two people, (one to run the motor, the other to watch the fluid) start the motor.
7. Run the motor until the fluid line begins spurting air. Shut motor off immediately!! The fluid will get quite frothy.
8. Allow to stand without the motor running for 4-5 minutes. This will let excess fluid in the trans drain down into the pan.
9. Start the motor again for no more than 5 seconds. Shut off the motor, This will pump out that last little bit in the pan and
make dropping the pan a lot less messy.
10. Let the oil lines drip into the pail while you drop the trans pan.
11. Drop the trans pan, and replace the filter using two (2) "O" rings at the filter.
12. Hook up the two trans lines to the oil cooler at the radiator.
13. Fill the trans with about 7 qts of trans fluid.
14. Start the motor and allow it to idle for about 30 seconds or so before checking fluid level.
15. Check fluid level and add accordingly.
16. Once full, drive until normal operating temp is reached, and recheck fluid level. Add fluid to bring to "Full".
I've used this procedure on every auto trans that I've owned for....well....forever. This is just the way I do it....your mileage
may vary.
Just my relatively informed, off the cuff, back yard mechanic, gut level, eyeball it up and guesstimate, way of doing
things....that's all...
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: Transmission Fluid Unknown Age [message #352770 is a reply to message #352760] |
Sat, 14 March 2020 21:13 |
Melbo
Messages: 144
Registered: August 2018
Location: Albuquerque NM
Karma: 0
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Larry
Thank you for the "plan" however you did not give any advice on which fluids to use. My coach is up in the air and I have oil pans to catch everything I will plan on Dexron and 90 wt.
Thanks
Melbo
Albuquerque NM Bus Conversion 1978 MCI 1973 GMC
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| Re: Transmission Fluid Unknown Age [message #352774 is a reply to message #352760] |
Sat, 14 March 2020 22:42 |
Scott Nutter
Messages: 782
Registered: January 2015
Location: Houston/San Diego
Karma: 4
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Thanks to Emery for the headlamp oil replacement reminder. It is amazing how many people forget/by pass this scheduled maintenance procedure. Another often overlooked recommended update is the addition of a inert gas additive to Co2 whistle Running any tire different than a 16.5. Methane gas from a grain only farm animal is most desirable, but honestly, any captured gas from animals ingesting any alfalfa products should work in a emergency situation. as long as it was humanly recovered. Could be the difference between life or breath....
Stand by for next weeks update...."how to use your toe nail clippings to modify your tires for winter use"...
Scott.
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, Dave Lenzi super duty mid axle disc brakes, tankless water heater, everything Lenzi. Alex Ferrera installed MSD Atomic EFI
Houston, Texas
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| Re: Transmission Fluid Unknown Age [message #352777 is a reply to message #352760] |
Sun, 15 March 2020 09:04 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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My transmission advice is DO NOT FLUSH. Change what you can get out by suction device through dipstick tube or the messy way dropping pan. I got out about 6.5 quarts after sitting a long time and torque converter drained back to the centerline. Drive it and do it again in a month or some miles later. After several changes it will appear clean. Many old varnished transmissions fail shortly after a full transfusion as the fresh fluid additives suddenly do too much cleaning. There are many "failed shortly after flush" stories on line. I have never had a failure using the gentle method. GM does not mention the flush method in service manual ( did not exist back then). The current most correct fluid to buy is the Dex/merc. Not ATF! I buy the Valvoline Dex/merc in gallons. As far as filter goes, if unsure of the Chinese filter, better to stay with used correct sized old one(.750 tube) than ruin trans with defective new filter. Or buy new one from a vendor that has screened them as good. Check level engine running, warm in Park.
John Lebetski
Woodstock, IL
77 Eleganza II
[Updated on: Sun, 15 March 2020 09:08] Report message to a moderator |
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| Re: Transmission Fluid Unknown Age [message #352779 is a reply to message #352760] |
Sun, 15 March 2020 11:17 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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I think it is a generally good idea to get a baseline on any new to you vehicle by changing all the fluids as soon as it is convenient to do so. The transmission fluid/filter is only a little bit more complicated than doing an oil change, same with the final drive.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Transmission Fluid Unknown Age [message #352780 is a reply to message #352760] |
Sun, 15 March 2020 12:47 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Also-- I'd never let anyone hook up a shop trans flusher machine to any vehicle I own. Who has been on the machine before you and was it properly"sanitized" of sludge and particulate matter that can ruin a valve body are the unknowns.
John Lebetski
Woodstock, IL
77 Eleganza II
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