Rear End FAQ!
I was bored Sunday so I looked at some of my gear ratio charts and came up with these ratios for the 4 rear ends often found in F body's might miss a few but they should give anyone a good idea feel free to add...
GM 7.5... 3.08 3.23 3.42 3.73 4.11 4.56
GM 8.5...2.73 3.08 3.42 3.73 3.90 4.10 4.56 5.13 5.57
Ford 8.8..3.08 3.55 3.73 4.10 4.30 4.56 4.88 5.13
Ford 9 inch..2.91 3.00 3.08 3.25 3.33 3.40 3.45 3.50 3.55 3.60 3.64 3.70 3.75 3.80 3.82 3.89 3.91 4.00 4.11 4.22 4.33 4.44 4.50 4.57 4.63 4.71 4.78 4.86 5.00 5.14 5.25 5.29 5.37 5.43 5.50 5.57 5.67 5.83 6.00 6.14 6.20 6.33 6.43 6.50 6.67 6.83 7.00 ...
difference in weight between a nodular and Iron center section is approx is 19 pounds if you run 35 or 40 spline axles you'll need a 3.250 dia carrier bearing third member keep in mind a set of 31 spline axles should cover 90% of people's builds
GM 7.5... 3.08 3.23 3.42 3.73 4.11 4.56
GM 8.5...2.73 3.08 3.42 3.73 3.90 4.10 4.56 5.13 5.57
Ford 8.8..3.08 3.55 3.73 4.10 4.30 4.56 4.88 5.13
Ford 9 inch..2.91 3.00 3.08 3.25 3.33 3.40 3.45 3.50 3.55 3.60 3.64 3.70 3.75 3.80 3.82 3.89 3.91 4.00 4.11 4.22 4.33 4.44 4.50 4.57 4.63 4.71 4.78 4.86 5.00 5.14 5.25 5.29 5.37 5.43 5.50 5.57 5.67 5.83 6.00 6.14 6.20 6.33 6.43 6.50 6.67 6.83 7.00 ...
difference in weight between a nodular and Iron center section is approx is 19 pounds if you run 35 or 40 spline axles you'll need a 3.250 dia carrier bearing third member keep in mind a set of 31 spline axles should cover 90% of people's builds
I think someone needs to mention how the Moser bolts slip. Even though we may not want to offend any particular company, it is a fact that the Moser design uses four bolts instead of two bolts that go directly through. Many readers of this site have still fallen victim to this including myself. Even when you buy a UMI torque arm for a 12 bolt there is a warning at the top of the instructions that torque arms broken due to moser bolts slipping are not covered under warranty.
I read a lot of set up specs that say to use less pinion bearing preload if your bearings are used, more if the bearings are new. You say to use more or less if the crush collar is new or used. Which is correct?
I hate sticky threads that just come to a dead end. I think it's an important point.
Everything I've ever read says use more preload with new bearings, less with used bearings. Now this says use more with a new crush collar, and come to think of it you're not even supposed to reuse the crush collar if you do it the right way.
So whats the word on pinion preload?
Everything I've ever read says use more preload with new bearings, less with used bearings. Now this says use more with a new crush collar, and come to think of it you're not even supposed to reuse the crush collar if you do it the right way.
So whats the word on pinion preload?
Originally Posted by John_D.
I always heard it was related to the crush sleeve, not the bearings. For a new crush sleeve, it takes more load to crush it down. But for a used one, that's already been done.
New bearing preload is tighter to anticipate the break in of new bearings becoming loose during break in, used bearings are already broken in and don't need as much.
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Originally Posted by Optimus_Prime
I forgot to say...Any rearend can hold an unlimited amount of horsepower....Until you start moving
Teching In
Joined: Mar 2006
Posts: 49
Likes: 1
From: Northwest Indiana
I am rebuilding a 10 bolt myself. It is a 2 series. What is the best differential for street and weekend races. I was thinking Auburn or possibly Eaton. Any suggestions would be well appreciated.
Also with a 2 series you need the thicker gears right or is that the 3 series, I'm confused.
Also with a 2 series you need the thicker gears right or is that the 3 series, I'm confused.
Thread Starter
TECH Addict
iTrader: (22)
Joined: Jan 2005
Posts: 2,928
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From: Mooresville, NC
Some helpful definitions of common rear-end terms:
Backlash – the play between the ring and pinion gear
Differential – a gear arrangement that allows the drive wheels to be driven at different speeds
C-clip – a c-shaped piece of metal used to retain an axle shaft
Coast – a load condition in which the vehicle is driving the engine, as during deceleration
Drive – a load condition where the engine is applying power to the drive wheels
Heel – the outer end of a gear tooth
Limited slip differential (LSD) – a differential that uses internal clutches to limit the speed difference between the axles.
Pinion depth – how deep the pinion gear is in the housing, where it contacts the ring gear
Race – a hardened surface for the bearing rollers/***** to roll on (kind of ‘cups’ the bearing)
Toe – the inner end of a ring gear tooth
Backlash – the play between the ring and pinion gear
Differential – a gear arrangement that allows the drive wheels to be driven at different speeds
C-clip – a c-shaped piece of metal used to retain an axle shaft
Coast – a load condition in which the vehicle is driving the engine, as during deceleration
Drive – a load condition where the engine is applying power to the drive wheels
Heel – the outer end of a gear tooth
Limited slip differential (LSD) – a differential that uses internal clutches to limit the speed difference between the axles.
Pinion depth – how deep the pinion gear is in the housing, where it contacts the ring gear
Race – a hardened surface for the bearing rollers/***** to roll on (kind of ‘cups’ the bearing)
Toe – the inner end of a ring gear tooth
Launching!
Joined: Aug 2002
Posts: 231
Likes: 0
From: Ontario, Canada
Here is a quick on for the FAQ masters!
When using a 9", 8.8 or 12 bolt housing, how would you handle things like your ABS functionality? The Moser/Strange rear's have provisions for this I know, but for homebuilts, is this something that can be addressed?
There is a shop locally that claims they can build me a 9" for my car. I have a 3 series carrier and 3 channel rear. Should I believe them? Is it as simple as drilling a hole in the top of the new 9" pumpkin and mounting the reluctor ring to the 9" carrier?
When using a 9", 8.8 or 12 bolt housing, how would you handle things like your ABS functionality? The Moser/Strange rear's have provisions for this I know, but for homebuilts, is this something that can be addressed?
There is a shop locally that claims they can build me a 9" for my car. I have a 3 series carrier and 3 channel rear. Should I believe them? Is it as simple as drilling a hole in the top of the new 9" pumpkin and mounting the reluctor ring to the 9" carrier?
Thread Starter
TECH Addict
iTrader: (22)
Joined: Jan 2005
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From: Mooresville, NC
Another question & answer:
Can't I just get a 9 inch out of a junkyard? I'm on a tight budget.
For this answer, I consulted Bob @ Exotic Performance plus.
Bob@EPP:
"Moser does not sell the torque arm mounting parts separate, so you would have to have them made for you. Welding the bosses on the rearend housing will typically warp the housing, so a jib fixture should be used to keep the housing in place until it cools. Warpage may still occur and the rear-end may have to be straightened once the torque arm mounts are installed.
The Moser 9" housing with the torque arm mount, pn# 7H9FBNT, retails from Moser for $510.00. For those trying to cut cost, I recommend purchasing the Moser housing, and picking up a used third member."
Can't I just get a 9 inch out of a junkyard? I'm on a tight budget.
For this answer, I consulted Bob @ Exotic Performance plus.
Bob@EPP:
"Moser does not sell the torque arm mounting parts separate, so you would have to have them made for you. Welding the bosses on the rearend housing will typically warp the housing, so a jib fixture should be used to keep the housing in place until it cools. Warpage may still occur and the rear-end may have to be straightened once the torque arm mounts are installed.
The Moser 9" housing with the torque arm mount, pn# 7H9FBNT, retails from Moser for $510.00. For those trying to cut cost, I recommend purchasing the Moser housing, and picking up a used third member."
how about this:
i just put my 9" in, and now when i hit a hard bump, the rear end feels like its hitting the floor?
the top of the torque arm mount can hit... usually its just the tip of the top bolt..
i put a 9" in and now the torque arm hits the trans tunnel...?
heh, theres a few aftermarket rear questions someone should type up.. if i remember, and i get the time, i'll do it..
i just put my 9" in, and now when i hit a hard bump, the rear end feels like its hitting the floor?
the top of the torque arm mount can hit... usually its just the tip of the top bolt..
i put a 9" in and now the torque arm hits the trans tunnel...?
heh, theres a few aftermarket rear questions someone should type up.. if i remember, and i get the time, i'll do it..
Thread Starter
TECH Addict
iTrader: (22)
Joined: Jan 2005
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From: Mooresville, NC
I had an aftermarket torque arm on my 12 bolt and it made so much racket, drove me ******* insane. I couldn't stand the constant banging & the amplification of the rear end noises. I would rather break torque arms every week then do that again!! lol
Originally Posted by maxxer442
So what about the oldsmobile 12 bolt? It's referred to as a 12 bolt, but only has 10 bolts holding the ring gear-but its got 12 cover bolts.
Other than parts availability (don't think anything interchanges w/ a Chevy rear), it's a solid rear end, as strong as any Chevy 8.5" rear (12 or 10 bolt).