Rear axle limited slip, ratio and 10 vs 12 bolt rear
April 7th, 2016, 09:34 PM
#1
Registered User
Thread Starter
Join Date: Dec 2014
Posts: 884
Rear axle limited slip, ratio and 10 vs 12 bolt rear
1.How do I determine if my cars rear axle is limited slip on a lift. I have been told that if the rear wheels when turned, turn in the same direction manually, then the rear is limited slip differential.
2. How do I tell if I have a 10 or 12 bolt rear. I've heard many stories on this.
3. How do I determine the rear axle ratio by turning the rear wheels with one revolution of the driveshaft.
Assume for these questions that the engine is off, no build sheet, invoice, no posi tag, and of course,no documentation.
The car is a 1970 442 with a turbohydomatic 400 transmission.
Thank you in advance for your help.
2. How do I tell if I have a 10 or 12 bolt rear. I've heard many stories on this.
3. How do I determine the rear axle ratio by turning the rear wheels with one revolution of the driveshaft.
Assume for these questions that the engine is off, no build sheet, invoice, no posi tag, and of course,no documentation.
The car is a 1970 442 with a turbohydomatic 400 transmission.
Thank you in advance for your help.
April 7th, 2016, 09:48 PM
#2
Registered User
Join Date: Jul 2006
Location: Richfield, Oh
Posts: 1,736
Id
1. usually both wheels are locked by clutches or cones in the behind the spider gears. Usually it will take some torque to break these components lose.
Usually YES both tires will spin in the same direction when the car IS IN NEUTRAL IT IS LIMITED SLIP (ANTI SPIN, POSI , TWIN GRIP, TRAC LOCK ETC.)
2.The 10 bolt 12 botl thing is all about the ring gear bolts.
So if the rear has 10 bolts it is a 10 bolt 12 bolts HOLDING THE RING GEAR IS 12 BOLT Sometimes the rear differential cover will match the ring gear bolt count...Some will not.
IE dana 60 is a 12 bolt ring with 10 bolt cover
IE 12 bolt oldsmobile has a 12 botl cover but 10 bolt ring gear so really ir is a 10 bolt rear end.
3. You have to mark the pinion and a reference spot to the housing (none moving part) and also mark the wheel axle flange to the drum backing plate and none moving part. Watch how many turns the pinion turns to the ONE REVOLUTION of the wheel / axle flange. that is yoru ration ... 3 to 1 or 3.75 to 1 etc,
This is for Limited slip diffs only not open differential (non Posi)
Jim
J D
Usually YES both tires will spin in the same direction when the car IS IN NEUTRAL IT IS LIMITED SLIP (ANTI SPIN, POSI , TWIN GRIP, TRAC LOCK ETC.)
2.The 10 bolt 12 botl thing is all about the ring gear bolts.
So if the rear has 10 bolts it is a 10 bolt 12 bolts HOLDING THE RING GEAR IS 12 BOLT Sometimes the rear differential cover will match the ring gear bolt count...Some will not.
IE dana 60 is a 12 bolt ring with 10 bolt cover
IE 12 bolt oldsmobile has a 12 botl cover but 10 bolt ring gear so really ir is a 10 bolt rear end.
3. You have to mark the pinion and a reference spot to the housing (none moving part) and also mark the wheel axle flange to the drum backing plate and none moving part. Watch how many turns the pinion turns to the ONE REVOLUTION of the wheel / axle flange. that is yoru ration ... 3 to 1 or 3.75 to 1 etc,
This is for Limited slip diffs only not open differential (non Posi)
Jim
J D
April 8th, 2016, 04:01 PM
#3
Registered User
Thread Starter
Join Date: Dec 2014
Posts: 884
Rear Axle Ratio and 10vs 12 bolt rear
Mr. Monzaz,
Thank you for your response. I'm still confused on the 1970 442 rear 10 vs 12 bolt. If I understand you clearly, you're saying that just because the cover has 12 bolts doesn't necessarily mean that it is a 12 bolt rear. In fact, a 12 bolt cover may contain a 10 bolt ring gear. Do the 442's come equipped with a 12 bolt ring gear? If not,will the 10 bolt ring gear withstand the torque from the starting line? Barring legitimate documentation, the sure way to determine if the ring gear is 12 bolt is to remove the cover and count the bolts?
Thanks again for your help.
Thank you for your response. I'm still confused on the 1970 442 rear 10 vs 12 bolt. If I understand you clearly, you're saying that just because the cover has 12 bolts doesn't necessarily mean that it is a 12 bolt rear. In fact, a 12 bolt cover may contain a 10 bolt ring gear. Do the 442's come equipped with a 12 bolt ring gear? If not,will the 10 bolt ring gear withstand the torque from the starting line? Barring legitimate documentation, the sure way to determine if the ring gear is 12 bolt is to remove the cover and count the bolts?
Thanks again for your help.
April 8th, 2016, 05:16 PM
#4
Registered User
Join Date: Feb 2013
Location: Phoenix, AZ
Posts: 13,738
Olds built its own rear from '67 to '70, which we call the O-Type. It has a 12 bolt cover and a 10 bolt ring gear, which is likely what your car has as that was the standard rear on Cutlasses in 1970. I have heard the Canadian built cars used the Chevy 12 bolt rear, and it is also possible the rear could have been changed in the past 46 years.
Only the Canadian cars with the Chevy 12 bolt.
That depends upon a few variables, such as your engine output, torque converter stall, rear tire traction, etc. The O-Type should be equivalent in strength to the later 8.5" corporate 10 bolt rears.
No need for that; it should be easy enough to ID the rear with some pictures.
Only the Canadian cars with the Chevy 12 bolt.
No need for that; it should be easy enough to ID the rear with some pictures.
April 8th, 2016, 09:04 PM
#6
Registered User
Join Date: Jul 2006
Location: Richfield, Oh
Posts: 1,736
Ring size
ALL rear ends are fine for the street. Worse thing you can let happen to a rear is low maintenance and they do not even ask for much at all. Change the oil every 3 years or so and your good... lol. ALL depends on the mileage and punishment you put the rear through.
10 bolt 12 bolt it is all moot on the street.
the track is the only place your going to destroy parts as long as the rear was build correctly.
If you do not live at the track your stock 10 bolt / 12 bolt etc will live fine doing burn outs on the street and taking your small or big block power and even some fun runs at the track at reasonable launch RPMs.
NOW if you have a stick shift and abuse the drive line a lot on the street that could be a need for a bit bigger beefier rear.
Ring gear size : you will measure the ring across the center furthest most outside of the circle to furthest outside across the tooth side.
Ring and Pinion usually are not your failure area. The spider gears will usually always be the weak link in the system. NOT too much you can do about that... BUY the newest unit you can as the metallurgy will usually again be the most updated. The more spider gear to side gear contact points will be the best to handle the torque load output.
SO that is the reason a lot of POWER LOCK DANA spicer units 4 pinion spider gear units and Super duty 4 pinion auburn units were revered as strong work horse units.
As better hardening came into being that was not as big a deal and 2 spider gears again were used and the cars started to loose power and torque also.
Later in the 90's they started to realize to make the side gears smaller and the pinion spider gear bigger to square up the size of the planetary gear in the open and posi unit was necessary also for better strength again
Now we have another shift to the Torsen type posi units the German and Japanese super cars ushered in. True trac etc (WORM GEAR POSI )supply a good 3 touch point to the side gears giving strength and the cases are hardened for the worm gears to slide through to keep there house stable they slide through from left to right engaging and disengaging the side gear to transfer power / torque % to the left or right drive wheels.
So hope that helps with more info again.
Jim
JD
10 bolt 12 bolt it is all moot on the street.
the track is the only place your going to destroy parts as long as the rear was build correctly.
If you do not live at the track your stock 10 bolt / 12 bolt etc will live fine doing burn outs on the street and taking your small or big block power and even some fun runs at the track at reasonable launch RPMs.
NOW if you have a stick shift and abuse the drive line a lot on the street that could be a need for a bit bigger beefier rear.
Ring gear size : you will measure the ring across the center furthest most outside of the circle to furthest outside across the tooth side.
Ring and Pinion usually are not your failure area. The spider gears will usually always be the weak link in the system. NOT too much you can do about that... BUY the newest unit you can as the metallurgy will usually again be the most updated. The more spider gear to side gear contact points will be the best to handle the torque load output.
SO that is the reason a lot of POWER LOCK DANA spicer units 4 pinion spider gear units and Super duty 4 pinion auburn units were revered as strong work horse units.
As better hardening came into being that was not as big a deal and 2 spider gears again were used and the cars started to loose power and torque also.
Later in the 90's they started to realize to make the side gears smaller and the pinion spider gear bigger to square up the size of the planetary gear in the open and posi unit was necessary also for better strength again
Now we have another shift to the Torsen type posi units the German and Japanese super cars ushered in. True trac etc (WORM GEAR POSI )supply a good 3 touch point to the side gears giving strength and the cases are hardened for the worm gears to slide through to keep there house stable they slide through from left to right engaging and disengaging the side gear to transfer power / torque % to the left or right drive wheels.
So hope that helps with more info again.
Jim
JD
April 8th, 2016, 09:21 PM
#7
Registered User
Join Date: Feb 2013
Location: Phoenix, AZ
Posts: 13,738
As stated previously, a '70 442 built in the U.S. would have come with an O-Type rear and a Canadian built would likely have a Chevy 12 bolt.
Last edited by Fun71; April 8th, 2016 at 09:24 PM.
April 8th, 2016, 09:31 PM
#8
Registered User
Thread Starter
Join Date: Dec 2014
Posts: 884
Hi Jim,
Thank you very much. You should add after Jim PHD!! What an education. What I learned is invaluable. As an example, change the oil in the rear once every three years isn't asking much at all. I also learned that when someone tells me their rear is a12 bolt rear that it is actually a 10 bolt ring gear. Again Jim, thanks for your patience and the education you have provided.
Thank you very much. You should add after Jim PHD!! What an education. What I learned is invaluable. As an example, change the oil in the rear once every three years isn't asking much at all. I also learned that when someone tells me their rear is a12 bolt rear that it is actually a 10 bolt ring gear. Again Jim, thanks for your patience and the education you have provided.
April 9th, 2016, 01:49 AM
#11
Registered User
Join Date: Nov 2008
Location: Redmond, Oregon
Posts: 3,326
If it is on the rack change the fluid. It is cheap and smart. While the cover is off it will have a ring and pinion teeth count on the edge of the ring gear. Like 40 13 or something like that. Divide them into each other and you have the ratio. 40 divided by 13 = 3.0769 or 3:08 and so on. This also give you a chance to inspect it and change the fluid and that is all good.
You can also see the carrier and it will be either an open with no posi clutches or it will be a posi ( limited slip, trac lock, and so on) Lots of terms for the same basic thing.
Pictures of the rear will help us help you. Also on the right axle tube between the center section and the right spring there usually is a code stamped into the tube. It is often upside down. This will help also.
You can also see the carrier and it will be either an open with no posi clutches or it will be a posi ( limited slip, trac lock, and so on) Lots of terms for the same basic thing.
Pictures of the rear will help us help you. Also on the right axle tube between the center section and the right spring there usually is a code stamped into the tube. It is often upside down. This will help also.
April 9th, 2016, 07:13 AM
#12
Registered User
Join Date: Jul 2006
Location: Richfield, Oh
Posts: 1,736
oIL
Hi Jim,
Thank you very much. You should add after Jim PHD!! What an education. What I learned is invaluable. As an example, change the oil in the rear once every three years isn't asking much at all. I also learned that when someone tells me their rear is a12 bolt rear that it is actually a 10 bolt ring gear. Again Jim, thanks for your patience and the education you have provided.
Thank you very much. You should add after Jim PHD!! What an education. What I learned is invaluable. As an example, change the oil in the rear once every three years isn't asking much at all. I also learned that when someone tells me their rear is a12 bolt rear that it is actually a 10 bolt ring gear. Again Jim, thanks for your patience and the education you have provided.
Jim
Thread
Thread Starter
Forum
Replies
Last Post
terrapin
General Discussion
4
November 22nd, 2012 11:53 AM
rickbmac
Drivetrain/Differentials
6
July 19th, 2008 04:51 PM
