Shopping For A Rear End... Some Questions

**Naaman** · 05-12-2010, 07:56 PM

I'm looking at some rear ends for a 98 Z convertible. My power goals are no more than 350 whp. It will be a daily driven street car that may or may not ever see a track.

Looking at different rear-ends, I'm noticing that I have to give certain info about my car in order to configure it. Also, I'm wondering exactly what makes the 10-bolt weak.

So, here are my questions:

1) The 10-bolt is 7.5 inches... what does that mean? What part of the car is the 7.5" referring to? My understanding is that it is this particular spec that makes it weak. If so, can I upgrade just that part, or do I have to buy an entire rear-end (center/gears/axles etc)? Is it possible to beef up the rear-end without spending $2000-3000?

2) Does my car have 3-channel or 4-channel ABS?

3) What are splines (are they teeth?) and what do they do? What difference will it make if I get 30, 33, or 35 spline? They are offered at the same/similar price, so are the different options more appropriate for different applications?

**Hi-Po** · 05-12-2010, 08:09 PM

Originally Posted by Naaman

I'm looking at some rear ends for a 98 Z convertible. My power goals are no more than 350 whp. It will be a daily driven street car that may or may not ever see a track.

Looking at different rear-ends, I'm noticing that I have to give certain info about my car in order to configure it. Also, I'm wondering exactly what makes the 10-bolt weak.

So, here are my questions:

1) The 10-bolt is 7.5 inches... what does that mean? What part of the car is the 7.5" referring to? My understanding is that it is this particular spec that makes it weak. If so, can I upgrade just that part, or do I have to buy an entire rear-end (center/gears/axles etc)? Is it possible to beef up the rear-end without spending $2000-3000?

2) Does my car have 3-channel or 4-channel ABS?

3) What are splines (are the teeth?) and what do they do? What difference will it make if I get 30, 33, or 35 spline? They are offered at the same/similar price, so are the different options more appropriate for different applications?

1) 7.5" refers to the actual ring gear itself. That is the diameter and no, you cannot squeeze a larger size in your 10 bolt housing. Beefing up the 10 bolt rear is kind of odd sentence to say/type. It will always have its weak links, and there is just no way around that.

2) Does your car have ASR/TCS? Does it have wheel speed sensors (WSS) on all 4 corners/wheels or just the back two? If its just the back two, you have a 3 channel, if you have a WSS on every corner you have a 4 channel. If you have ASR/TCS, you have a 4 channel.

3) splines refer to the number of 'teeth' at the end of the axle shaft the is inserted into the differential. They are attached to the axle shaft and in turn applies power the the wheel. Usually a 35 spline axle will only be a spool/locker/ or the recently available WaveTrac.

Hope that answers your questions, read the sticky at the top of this section and watch the videos. Read all the Wiki links and I'm sure you will have a better grasp on this situation.

**Naaman** · 05-20-2010, 05:24 AM

Originally Posted by Hi-Po

1) 7.5" refers to the actual ring gear itself. That is the diameter and no, you cannot squeeze a larger size in your 10 bolt housing. Beefing up the 10 bolt rear is kind of odd sentence to say/type. It will always have its weak links, and there is just no way around that.

Okay, got it. Does that also mean that I cannot just get a larger housing and put in a larger gear without buying a whole rear end?

Originally Posted by Hi-Po

2) Does your car have ASR/TCS? Does it have wheel speed sensors (WSS) on all 4 corners/wheels or just the back two? If its just the back two, you have a 3 channel, if you have a WSS on every corner you have a 4 channel. If you have ASR/TCS, you have a 4 channel.

I have no idea if it has wheel speed sensors on each rear wheel. It does not have ASR/TCS to my knowledge (there is no dash mounted switch next to the fog lights)

Originally Posted by Hi-Po

3) splines refer to the number of 'teeth' at the end of the axle shaft the is inserted into the differential. They are attached to the axle shaft and in turn applies power the the wheel. Usually a 35 spline axle will only be a spool/locker/ or the recently available WaveTrac.

Still lost on this one... what reason is there to have more or less teeth? The gear ratios and "splines" are selected as different options, so it seems like there is more to it than just the gearing.

Originally Posted by Hi-Po

Hope that answers your questions, read the sticky at the top of this section and watch the videos. Read all the Wiki links and I'm sure you will have a better grasp on this situation.

I've checked out all that stuff. Great info. I have a basic understanding of how a powertrain works (took a semester of auto shop in college), but some of the specifics are still a mystery to me

**35th-ANV-SS** · 05-20-2010, 10:17 AM

The larger the number of teeth, the more contact the axle has with the mating differential. Therefore, the more teeth the stronger the axle shaft is. Example: 35 spline is stronger than 31 spline.

A WSS is a device that is mounted in the backing plate (looks like a little solenoid with a small shaft sticking out of the end that is magnetic). The magnetic part of it senses how many times the reluctor ring on the end of the axle shaft turns (the reluctor ring is a ring with teeth on it). This in turn lets the computer know how fast each wheel is turning at all times. This is how it knows when to apply TCS or ABS when needed. This is how it works for a 4 channel with ABS/TCS. A 3-channel system will have the WSS on the pumpkin I believe (the center section of the rear end) and not at each wheel.

**Naaman** · 05-21-2010, 11:05 PM

So the more teeth the better? If they all cost the same, why would anyone want fewer splines?

**35th-ANV-SS** · 05-22-2010, 07:54 AM

Good question! I went with a 31 spline as that's the strongest rated axle that you can get with the TruTrac. 35 spline are only offered for lockers. My best response is weight. A 28 spline axle will neck down and become smaller in diameter and then will have larger teeth so it will weigh less than a 31 spline or 35 spline. There might be a different answer, but that's all I have

.

**pajeff02** · 05-22-2010, 10:17 AM

Lots of info in this thread: http://www.ls1.com/forums/showthread.php?t=125182 Also, here's a pic of the 28 spline stocker and 33 spline Moser axle for comparison:

**zmg00camaross** · 05-23-2010, 09:51 AM

OP is your car a auto or a manual car. if auto probly never have to upgrade the rear with your goals.

**tatertot91** · 05-23-2010, 09:57 AM

Originally Posted by zmg00camaross

OP is your car a auto or a manual car. if auto probly never have to upgrade the rear with your goals.

Well depending on gearing and whether or not a stall is going in there a stronger rear is good insurance.

**zmg00camaross** · 05-23-2010, 10:49 AM

Originally Posted by tatertot91

Well depending on gearing and whether or not a stall is going in there a stronger rear is good insurance.

Yeah stock gearing probly be ok. but OP said 350 RWHP which is full bolt ons. Myself have a 9 inch and love the insurance of it under my car.

**hutcher04** · 05-23-2010, 01:40 PM

what is trac-loc, locker, and wave track?

**Naaman** · 05-25-2010, 08:06 AM

Originally Posted by zmg00camaross

OP is your car a auto or a manual car. if auto probly never have to upgrade the rear with your goals.

Its an M6.

**35th-ANV-SS** · 05-25-2010, 09:03 AM

Originally Posted by hutcher04

what is trac-loc, locker, and wave track?

Read this.

http://www.ls1.com/forums/showthread.php?t=128718

**spordee1** · 08-11-2010, 04:53 AM

Used 12 bolts which are 8.75 inches, are an excellent buy, there are a lot of 3 channel coming onto the market if you do not plan to beat the heck out of your rear end. 8.8 Ford which is 8.8" is another alternative good buy for your money to get around cost. King of the Hill is the 9" slightly more in cost, built for abuse, and in some situations might consume 15 hp to operate it. The 9" trutrac is a 31 spline bargain because many owners are trying to sell because they are failing under severe abuse.
All that said, I reccomend a used complete 12 bolt 3 channel. My second choice would be the trutrac, either for $1200.00 to $1500.00.