Me again :-/ - The 1947 - Present Chevrolet & GMC Truck Message Board Network

RedSierra · 10-06-2012, 03:49 PM

I'm trying to find a detailed description of how to remove the transmission from my 1986 Gmc Sierra. I have to replace the rear main seal.
I'm really new to this kind of thing so I thank everyone ahead of time for babysitting me.
Any ideas where I can get this info?
Thanks
RedSierra
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1981Stepside · 10-06-2012, 05:15 PM

It's pretty easy. A lot easier if you have a hoist. Disconnect your battery first. Disconnect and remove your starter motor. Also remove the cotter pin connecting your transmission linkage to your steering column, and pop the linkage free. Unscrew the speedo cable from the drivers side of the transmission. If you have a 700r4 trans, you'll need to remove the tv cable from the pass. side. It's held in with one bolt, and the cable is hooked into the trans on another cable. You'll have to half pull it out to see the connection. There is also an electrical pigtail the needs to be unplugged. Also remove the trans dipstick tube. There is one bolt up the tube holding it steady. Once that's out, it should just pull out.
Remove the 4 bolts connecting the drive shaft to the rear differential yoke. Have a drain pan under the back of the transmission as you pull out the drive shaft. You'll lose some fluid. Your choice whether to drain the rest of the fluid by dropping the pan. It'll make it lighter if you're doing this alone and on the ground.
Put a floor jack (or tranny jack if you're on a hoist) under the rear of the transmission to support it (try to get it between the trans mount and the pan to avoid putting too much stress on the tailshaft). Remove the torque converter access cover and remove the bolts connecting your flywheel and torque converter. You'll need to spin the flywheel to get them all. Usually a breaker bar on the crank pulley will do the trick.
Loosen and remove the transmission mount/crossmember - keep that jack in place for safety. If on the ground, put another floor jack under the front of the transmission, loosen and remove the bell housing bolts. Give a good shake and the transmission should pop free of the guide pins. Be careful when you're moving it free so it doesn't fall and land on you.
Someone chime in if I've missed anything.

Takes longer to describe than to actually drop the trans. Just take it slow, and you'll be okay. Also good to have someone here who has done it before to guide you through the process. Good luck!

RedSierra · 10-06-2012, 05:36 PM

Thanks A Ton!
Im a little anxious about getting it out but really want to give it a try.
Stay Tuned and Thanks again!
RedSierra

RedSierra · 10-06-2012, 06:24 PM

I got the truck up and got underneath and saw this...
Seems like a lot of oil everywhere.
Not sure where it's coming from.

INSIDIOUS '86 · 10-06-2012, 08:48 PM

Check your valve cover gaskets too
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RedSierra · 10-06-2012, 09:57 PM

Will do.
Keep em coming!
Thanks
RedSierra
Posted via Mobile Device

**hatzie** · 10-08-2012, 08:50 PM

Replace the front transmission seal too.

76Charlie · 10-09-2012, 04:59 PM

Rear seal will always leak, its not really a seal, it is ridged, it leaks less when you drive and leaks more when you let the truck sit.

RedSierra · 10-09-2012, 05:10 PM

Thanks! Im guessing it is hard to tell anything from my pictures above :-/
Red Sierra

ont_guy_38 · 10-09-2012, 05:11 PM

I would be checking that the intake gaskets , valve cover gaskets and oil pressure sending unit are not leaking before i took the tranny out .

ont_guy_38 · 10-09-2012, 05:16 PM

Just reach in behind the distributor along the rear of the block and along the top of the heads . You can usually tell if it,s pretty fresh oil or not

76Charlie · 10-09-2012, 05:23 PM

I have a rebuilt 454 in my truck and im still leaking oil, small from the valve cover gasket, the rest is coming through the hole in the bottom of my fly wheel cover(rear seal), that hole is there for that reason, the rear main seal leaks.

Your41Plague12 · 10-09-2012, 05:57 PM

If the engine in your truck is original, you should have a 1 piece rear main seal. 1986 was the first year for this. It is a lot less prone to leaking than its two-part counterpart. When you order parts, make sure you get one for a 1986 if the engine is original. If the engine is older, use any year before 1986.

Hulk Will Smash · 10-09-2012, 06:20 PM

Big blocks are like old Harleys... If its not leaking oil it means there's no oil in it... It's not if, it's how much it leaks that should be the focus of your attention.

Good luck with you project!
Posted via Mobile Device

10-06-2012, 03:49 PM	#1
RedSierra Registered User Join Date: Jul 2012 Location: Branson Mo Posts: 53	Me again :-/ I'm trying to find a detailed description of how to remove the transmission from my 1986 Gmc Sierra. I have to replace the rear main seal. I'm really new to this kind of thing so I thank everyone ahead of time for babysitting me. Any ideas where I can get this info? Thanks RedSierra Posted via Mobile Device

10-06-2012, 05:15 PM	#2
1981Stepside Registered User Join Date: Jan 2011 Location: Port Coquitlam, BC Posts: 202	Re: Me again :-/ It's pretty easy. A lot easier if you have a hoist. Disconnect your battery first. Disconnect and remove your starter motor. Also remove the cotter pin connecting your transmission linkage to your steering column, and pop the linkage free. Unscrew the speedo cable from the drivers side of the transmission. If you have a 700r4 trans, you'll need to remove the tv cable from the pass. side. It's held in with one bolt, and the cable is hooked into the trans on another cable. You'll have to half pull it out to see the connection. There is also an electrical pigtail the needs to be unplugged. Also remove the trans dipstick tube. There is one bolt up the tube holding it steady. Once that's out, it should just pull out. Remove the 4 bolts connecting the drive shaft to the rear differential yoke. Have a drain pan under the back of the transmission as you pull out the drive shaft. You'll lose some fluid. Your choice whether to drain the rest of the fluid by dropping the pan. It'll make it lighter if you're doing this alone and on the ground. Put a floor jack (or tranny jack if you're on a hoist) under the rear of the transmission to support it (try to get it between the trans mount and the pan to avoid putting too much stress on the tailshaft). Remove the torque converter access cover and remove the bolts connecting your flywheel and torque converter. You'll need to spin the flywheel to get them all. Usually a breaker bar on the crank pulley will do the trick. Loosen and remove the transmission mount/crossmember - keep that jack in place for safety. If on the ground, put another floor jack under the front of the transmission, loosen and remove the bell housing bolts. Give a good shake and the transmission should pop free of the guide pins. Be careful when you're moving it free so it doesn't fall and land on you. Someone chime in if I've missed anything. Takes longer to describe than to actually drop the trans. Just take it slow, and you'll be okay. Also good to have someone here who has done it before to guide you through the process. Good luck! __________________ Proud UA member since 2009 My LT1 Silverado build-up: http://67-72chevytrucks.com/vboard/s...d.php?t=549660 Check out my new YouTube channel! - https://youtube.com/channel/UCXk5mZOQI1sEnu5bIkhe7fA

10-06-2012, 05:36 PM	#3
RedSierra Registered User Join Date: Jul 2012 Location: Branson Mo Posts: 53	Re: Me again :-/ Thanks A Ton! Im a little anxious about getting it out but really want to give it a try. Stay Tuned and Thanks again! RedSierra

10-06-2012, 06:24 PM	#4
RedSierra Registered User Join Date: Jul 2012 Location: Branson Mo Posts: 53	Re: Me again :-/ I got the truck up and got underneath and saw this... Seems like a lot of oil everywhere. Not sure where it's coming from. Attached Images

10-06-2012, 08:48 PM	#5
INSIDIOUS '86 Registered User Join Date: Jul 2009 Location: washington Posts: 4,178	Re: Me again :-/ Check your valve cover gaskets too Posted via Mobile Device __________________ 377 sbc thumpr cam autogear m23 muncie 3:73 Detroit trutrac 3''spintech prostreet mufflers xpipe 1 3/4 headers build thread !http://67-72chevytrucks.com/vboard/s...d.php?t=577217 Iroc gauge threadhttp://67-72chevytrucks.com/vboard/s...d.php?t=554511

10-06-2012, 09:57 PM	#6
RedSierra Registered User Join Date: Jul 2012 Location: Branson Mo Posts: 53	Re: Me again :-/ Will do. Keep em coming! Thanks RedSierra Posted via Mobile Device

10-08-2012, 08:50 PM	#7
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,977	Re: Me again :-/ Replace the front transmission seal too. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.

10-09-2012, 04:59 PM	#8
76Charlie Registered User Join Date: Jan 2012 Location: henderson nevada Posts: 200	Re: Me again :-/ Rear seal will always leak, its not really a seal, it is ridged, it leaks less when you drive and leaks more when you let the truck sit. __________________ 1976 GMC SIERRA CLASSIC CAMPER SPECIAL! 454 BIG BLOCK BABY!

10-09-2012, 05:10 PM	#9
RedSierra Registered User Join Date: Jul 2012 Location: Branson Mo Posts: 53	Re: Me again :-/ Thanks! Im guessing it is hard to tell anything from my pictures above :-/ Red Sierra

10-09-2012, 05:11 PM	#10
ont_guy_38 Registered User Join Date: Jul 2007 Location: Ontario Canada Posts: 1,006	Re: Me again :-/ I would be checking that the intake gaskets , valve cover gaskets and oil pressure sending unit are not leaking before i took the tranny out . __________________ 1985 C10 2004 Avalanche

10-09-2012, 05:16 PM	#11
ont_guy_38 Registered User Join Date: Jul 2007 Location: Ontario Canada Posts: 1,006	Re: Me again :-/ Just reach in behind the distributor along the rear of the block and along the top of the heads . You can usually tell if it,s pretty fresh oil or not __________________ 1985 C10 2004 Avalanche

10-09-2012, 05:23 PM	#12
76Charlie Registered User Join Date: Jan 2012 Location: henderson nevada Posts: 200	Re: Me again :-/ I have a rebuilt 454 in my truck and im still leaking oil, small from the valve cover gasket, the rest is coming through the hole in the bottom of my fly wheel cover(rear seal), that hole is there for that reason, the rear main seal leaks. __________________ 1976 GMC SIERRA CLASSIC CAMPER SPECIAL! 454 BIG BLOCK BABY!

10-09-2012, 05:57 PM	#13
Your41Plague12 Registered User Join Date: Dec 2010 Location: Pittsburgh, PA Posts: 1,009	Re: Me again :-/ If the engine in your truck is original, you should have a 1 piece rear main seal. 1986 was the first year for this. It is a lot less prone to leaking than its two-part counterpart. When you order parts, make sure you get one for a 1986 if the engine is original. If the engine is older, use any year before 1986. __________________ Steve Member of the Foot Pedal Club '83 Chevy K20: 6" Rough Country, 3" Performance Accessories BL, Bushwacker Cutouts, 38x15.50 Mickey Thompson Baja Claws, 350 HP 350 crate engine from Jegs, Turbo 400

10-09-2012, 06:20 PM	#14
Hulk Will Smash Registered User Join Date: Apr 2006 Location: Huntington Beach, CA Posts: 492	Re: Me again :-/ Big blocks are like old Harleys... If its not leaking oil it means there's no oil in it... It's not if, it's how much it leaks that should be the focus of your attention. Good luck with you project! Posted via Mobile Device __________________ '87 R30 Crew Cab Dually It's 11 PM, do you know where your IAC pintle is?



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