Rear ends, how do they work? Options

[SlowCelica94]

Since I've been looking into ls1 FC's, a lot of talk has been about the streagth of rear ends. So how does a rear end work? What's it consist of? Thanks guys

[Supersprynt]

huh?

[shid]

I'm with you super..

[SlowCelica94]

like guys talk about a 4.10 rear end. The gears, you've never heard the term rear ends?

[Supersprynt]

I'm pretty sure ur talking about limited slip or something which doesnt apply to our cars.

This post has been edited by Supersprynt: Dec 1, 2004 - 3:12 PM

[Ale_lock]

Automotive gear ratio is most easily explained as the number of turns of the drive wheels in relation to the number of turns of the engine.  Basically , if the engine is considered the input and the drive wheel is considered the output, then the input gear or pinion meshes with the output gear or ring gear to drive or rotate it. The number of teeth on each gear determines the ratio.  For example: A rear end pinion gear may have 15 teeth that mesh with a ring gear that has 45 teeth; mathematically (45/15) this yields 3.00 ratio. This means that the engine will turn 3.00 times for each turn of the drive wheels. Most manual transmission RX-7's came with a 4.10 rear ends, while most RX-7 automatics came with a 3.90 rear end.  A ratio of 4.10 means the engine turns 4.10 times as fast as the wheels.  A 4:10 rear end will help with low end torque which is great for a Rotary powered RX-7 because a Rotary engine does not produce a lot of torque.  However, a 4.10 rear end at high speeds means that  the engine RPM's will also be high because the engine is turning 4 times faster then the wheels.  Example:  A stock Rotary powered engine with a 4:10 rear end and stock tires going about 80 mph on a freeway would be cruising at about 3,500 RPM.  Since a Rotary engine redlines anywhere from 7,000-8,000 RPM's (depending on  the year) 3,500 is a comfortable cruising RPM for a Rotary engine.  Looking at the charts above, a GM Borg Warner (B/W) T-5 (5-speed) gearing is similar to the RX-7 5-speed gearing, so, at first,  it sounds like a good Hybrid RX-7 choice - but is it the best choice?  Since the B/W gearing is similar to the Rotary gearing, this means at 80 MPH you're still doing about 3,500 RPM's, but now you're doing 3,500 on a V8 engine that probably Redlines at about 5,500 RPM's.  This is why you want to choose a transmission with an overdrive,  let's say you install, a GM TH350 (Turbo 350) that has a 1.00 final gear and you have a  4.10 rear end, now at 80 MPH, you'll be spinning at about 4,500 RPM's (yikes!).

Borrowed off a site. It's starting to make sense after a few reads.

edit: I'll keep looking up more info.

This post has been edited by Meonspeed: Dec 1, 2004 - 3:15 PM

[Supersprynt]

Maybe its the final gear ratio, average gear ratio?

[bufferdan]

RWD cars like camaros/mustangs have a rear axel that has a differential in the center to distribute power. The drive shaft runs from the tranny to the rear differential...

3.73...4.11...thats just differential gear ratios.

[bufferdan]

you can swap out the differential gears to change the ratio also...4.11 gearing is very low...you will be reving in the higher rpms at highway speeds then you would with 3.73 gears. Its a pretty basic setup on rwd cars.

[Supersprynt]

ahhhhhhhhhh yes makes sense cuz its widely talked about with trucks and stuff for towing and whatnot.

[bufferdan]

http://auto.howstuffworks.com/differential.htm

have fun

[Ale_lock]

REAR END UPGRADES

Brought to you by: SONOMA96

By changing your stock taller rear end gears (numerically lower) with shorter gears (numerically higher), you can significantly improve the acceleration of your vehicle. When selecting the right gear ratio for your particular application, you must take into consideration many factors like your current and future modifications, as well as what type of driving you do most, along with rpm findings showing where in the rpm range it went from one gear at max shift to power range of the motor in the next gear. Typically vehicle equipped with taller gears, i.e. 2.73, 3.08, etc. trade slower acceleration for better high-speed performance. On the other hand, cars equipped with shorter gears, i.e. 3.73, 4.10, etc. will accelerate much quicker in the 1/4 mile but have a lower top speed. Gear ratios of 4.10 and higher should be reserved for the normally aspirated vehicles strictly set up for drag racing. Enthusiasts running high horsepower turbos, blowers, and or nitrous applications do not need as much gearing. These drivers generally limit the rear gear ratio of their vehicles to 3.73 and lower.

Since automatic-equipped vehicles are at a disadvantage to begin with, they seem to benefit much more by gear changes. This will in many cases bring the automatic cars up to par with the stock stick cars. In addition, the automatic enthusiasts will have the added comfort of not missing shifts and easier "hook up".

When upgrading the rear gear ratios on a stick-equipped vehicle, some drivers may initially have a harder time "hooking up" during racing or spirited driving. These drivers may have to adjust their driving technique and or purchase stickier tires/slicks to obtain proper traction.

The bottom line is that upgrading your rear gear ratio by two steps you can decrease your 1/4 of a mile times by approximately 3 tenths of a second. This is equivalent to finding 30 horsepower hidden under your hood. I think you would agree that hidden horsepower is always a good thing!!!

[Digndoug]

eh. never mind you guys coverd most of it

[97sccelica]

rear end could also mean the whole rear drivetrain/suspension

guys with V8 powered datsun z's tend to break everything back there.

some swap to an r200 differential and CV shafts which are several times stronger then beaf up the suspension

some convert to sold read axel

some use corvette c4 rear ends.

im sure its the same situation for an FC. car was never designed for the size and shape of a powerful v8's powerband, much like the datsun z's

[SlowCelica94]

Thanks ale, thats what I was talking about. Is any ratio more durable to power then another?

[FallenHero]

guys with V8 powered datsun z's tend to break everything back there.


[right][snapback]215379[/snapback][/right]

Seen it happen... it was beautiful.

Basically, the rear end transfers power from the drive shaft to the axle shafts. These old school datsun guys get a mean LS1 or such engine that has great power, and a great tranny. When they put big tires on, they get great traction. Hp is no problem, but that 3-400 lbs of torque have to go somewhere. The tranny is Plenty strong to handle it, but that little basket in the back just isn't up to the task.

This post has been edited by FallenHero: Dec 1, 2004 - 4:33 PM

[Fox-N-It2]

rear end could also mean the whole rear drivetrain/suspension

guys with V8 powered datsun z's tend to break everything back there.

some swap to an r200 differential and CV shafts which are several times stronger then beaf up the suspension

some convert to sold read axel

some use corvette c4 rear ends.

im sure its the same situation for an FC.  car was never designed for the size and shape of a powerful v8's powerband, much like the datsun z's
[right][snapback]215379[/snapback][/right]

Stock Turbo II FC drive lines will handle a 3 rotor so a V8 is no problem. They are good up to 400+. They also make a kit for FC's to use a ford rear end.

www.rx7club.com

Many there have ls1 FC swaps.

[SlowCelica94]

a lot of guys will use ****ty tires so they just spin, thus the power doesnt hit the ground. When hi torque cars hook up instantly (slicks) the rear end is more likely to bust.

[SlowCelica94]

a lot of guys will use ****ty tires so they just spin, thus the power doesnt hit the ground. When hi torque cars hook up instantly (slicks) the rear end is more likely to bust.

[SlowCelica94]

a lot of guys will use ****ty tires so they just spin, thus the power doesnt hit the ground. When hi torque cars hook up instantly (slicks) the rear end is more likely to bust.