filling a 12 bolt? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Goffer · 01-02-2005, 04:58 PM

The fill plug for the rear end is on the inspection cover, right? I don't see any way to fill my rearend the cover is solid and the only opening is the vent. it's a 12 bolt. could use a little help, I had to open it up to figure out what my ratio was.

skokie · 01-02-2005, 05:00 PM

Look for either a 3/8s hole that you would put a 3/8 ratchet into or a square bolt that takes a 5/8 wrench. You will need to open that to get the fluid into. My advice is getting the fluid that has a pump and a 2 foot hose attached to it. Much easier to fill it with the rear end under the truck.

Goffer · 01-02-2005, 05:06 PM

looked but cannot find... where is it. I'm starting to feel really dumb.

skokie · 01-02-2005, 05:08 PM

Let me get a pic for you. Be right back.

Goffer · 01-02-2005, 05:14 PM

found it. completly cover in grease, it was hard to find. Thanx for the help

skokie · 01-02-2005, 05:15 PM

Mine was the same. Completely covered in dirt. When I hit it with the brake cleaner is when I saw it. Just curious but what gear do you have in there?

Goffer · 01-02-2005, 06:40 PM

to find the gear ratio was the reason for opening it up. The guy who sold it to me had no idea. But know I know it's 3.07. My tranny went out this weekend th400. So I've decided to go with a 700r4 getting ready for the swap.

jmanz69 · 01-02-2005, 08:55 PM

You will get awsome milage with a 700-R4 and a 3.07 gear. The 700 will even help overcome the high gear off lights with it's low 1st gear ratio. It'll be more fun to drive now. Just don't put too much HP and torque to that 700, they aren't made for it and will go out. A stock or mild engine will be fine though.

Goffer · 01-02-2005, 09:05 PM

Yep. This truck is my daily driver not a racer. It has enough pedal (for now) to still be fun. I got this truck, so I could work on it (Oppose to a newer car and all that crap they put on ‘em), and I love it's style; hair stands up on the back of my neck every time a rice burner with coffee can exhaust scream by my house.

Goffer · 01-02-2005, 09:06 PM

looking at Bowtie overdrives for the 700r4. I've heard good things.

phanatic32212 · 04-24-2005, 02:44 PM

I was reading this post and I found my fill plug. My question is, is the diff not supposed to be full? The fill plug is on the side, but a little higher than halfway, right?

Thanks

jmanz69 · 04-24-2005, 03:22 PM

You fill it until it come out the hole. That's all in needs. Be sure to use gear fluid. If you have a "posi", use the friction modifier as well. Be sure the axle is level front to back AND side to side before filling.

phanatic32212 · 04-25-2005, 04:09 AM

I do have a posi unit, but what is a friction modifier?

jku72 · 04-25-2005, 04:29 AM

Virtually every new bottle of 80/90 weight has the posi additives already in it. There was a time when this was not true, and if your not sure, it says right on the lable. Since you have to fill it anyway, you ought to add synthetic.

FirstGen · 04-25-2005, 12:39 PM

Quote:

Originally Posted by jku72

Virtually every new bottle of 80/90 weight has the posi additives already in it. There was a time when this was not true, and if your not sure, it says right on the lable. Since you have to fill it anyway, you ought to add synthetic.

actually some limited slips will not work right with synthetic, like for instance the Eaton posi's... all the friction modifier does is allow the clutches to slip a little when you turn so it doesn't make a bunch of noise. You can just fill it up and then add a little till the noise goes away around turns... That assures you have just enough to not be anoying but you aren't allowing the clutches to slip too much.

01-02-2005, 04:58 PM	#1
Goffer Registered User Join Date: Apr 2004 Location: Commerce City, CO Posts: 66	filling a 12 bolt? The fill plug for the rear end is on the inspection cover, right? I don't see any way to fill my rearend the cover is solid and the only opening is the vent. it's a 12 bolt. could use a little help, I had to open it up to figure out what my ratio was. __________________ '71 C10 swb 350sb/700r4

01-02-2005, 05:00 PM	#2
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,354	Look for either a 3/8s hole that you would put a 3/8 ratchet into or a square bolt that takes a 5/8 wrench. You will need to open that to get the fluid into. My advice is getting the fluid that has a pump and a 2 foot hose attached to it. Much easier to fill it with the rear end under the truck. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

01-02-2005, 05:06 PM	#3
Goffer Registered User Join Date: Apr 2004 Location: Commerce City, CO Posts: 66	looked but cannot find... where is it. I'm starting to feel really dumb. __________________ '71 C10 swb 350sb/700r4

01-02-2005, 05:08 PM	#4
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,354	Let me get a pic for you. Be right back. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

01-02-2005, 05:14 PM	#5
Goffer Registered User Join Date: Apr 2004 Location: Commerce City, CO Posts: 66	found it. completly cover in grease, it was hard to find. Thanx for the help __________________ '71 C10 swb 350sb/700r4

01-02-2005, 05:15 PM	#6
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,354	Mine was the same. Completely covered in dirt. When I hit it with the brake cleaner is when I saw it. Just curious but what gear do you have in there? __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

01-02-2005, 06:40 PM	#7
Goffer Registered User Join Date: Apr 2004 Location: Commerce City, CO Posts: 66	to find the gear ratio was the reason for opening it up. The guy who sold it to me had no idea. But know I know it's 3.07. My tranny went out this weekend th400. So I've decided to go with a 700r4 getting ready for the swap. __________________ '71 C10 swb 350sb/700r4

01-02-2005, 08:55 PM	#8
jmanz69 Careful, they attack... Join Date: Aug 2001 Location: Waterford, MI, USA Posts: 1,107	You will get awsome milage with a 700-R4 and a 3.07 gear. The 700 will even help overcome the high gear off lights with it's low 1st gear ratio. It'll be more fun to drive now. Just don't put too much HP and torque to that 700, they aren't made for it and will go out. A stock or mild engine will be fine though.

01-02-2005, 09:05 PM	#9
Goffer Registered User Join Date: Apr 2004 Location: Commerce City, CO Posts: 66	Yep. This truck is my daily driver not a racer. It has enough pedal (for now) to still be fun. I got this truck, so I could work on it (Oppose to a newer car and all that crap they put on ‘em), and I love it's style; hair stands up on the back of my neck every time a rice burner with coffee can exhaust scream by my house. __________________ '71 C10 swb 350sb/700r4

01-02-2005, 09:06 PM	#10
Goffer Registered User Join Date: Apr 2004 Location: Commerce City, CO Posts: 66	looking at Bowtie overdrives for the 700r4. I've heard good things. __________________ '71 C10 swb 350sb/700r4

04-24-2005, 02:44 PM	#11
phanatic32212 It's Done When It Runs!! Join Date: Sep 2002 Location: Jacksonville, FL (Orange Park) Posts: 220	I was reading this post and I found my fill plug. My question is, is the diff not supposed to be full? The fill plug is on the side, but a little higher than halfway, right? Thanks __________________ Or Give Me DEATH

04-24-2005, 03:22 PM	#12
jmanz69 Careful, they attack... Join Date: Aug 2001 Location: Waterford, MI, USA Posts: 1,107	You fill it until it come out the hole. That's all in needs. Be sure to use gear fluid. If you have a "posi", use the friction modifier as well. Be sure the axle is level front to back AND side to side before filling.

04-25-2005, 04:09 AM	#13
phanatic32212 It's Done When It Runs!! Join Date: Sep 2002 Location: Jacksonville, FL (Orange Park) Posts: 220	I do have a posi unit, but what is a friction modifier? __________________ Or Give Me DEATH

04-25-2005, 04:29 AM	#14
jku72 Registered User Join Date: Jan 2002 Location: cornville, maine Posts: 659	Virtually every new bottle of 80/90 weight has the posi additives already in it. There was a time when this was not true, and if your not sure, it says right on the lable. Since you have to fill it anyway, you ought to add synthetic. __________________ jku Cornville, Maine 68 C10 burb 42 Willys MB 46 Dodge WF-32 1.5 ton 53 & 56 Olds' 60 Cadillac 22 Dodge Brothers



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