8 inch rear end

ballajb64 · Feb 17, 2009

I am doin the EFI swap into my Mustang. I have a built motor that will put out maybe around 325rwhp. Will my 8 inch rear end stand up to this power?

Stang_1973 · Feb 17, 2009

Ive heard of 8 inchers handling up to 500 hp, but im guessing thats at the crank.

Ive been looking into upgrading my rear end as well. So far ive found that finding parts for te ole 8" isnt very easy. That and upgrading to posi is pretty expensive, $400+ just for the unit. Ive looked at upgrading to a 9 but thatll cost over a grand easy... anyway thats what ive found thus far.

If anybody else has some input im interested to hear it as im in a similair situation.

ballajb64 · Feb 17, 2009

yea i came up wit the same price for the unit in unlimited mustang book. How does the car feel though with the 8 inch open?

rbohm · Feb 17, 2009

the 8" will handle the power your engine is putting out with few issues. you can even run slicks if you want. check out currie enterprises for 8" performance parts. the cost of building an 8" and a 9" is going to be about the same overall. differentials, gears, axles, bearings, etc. are all about the same price.

Decurion · Feb 17, 2009

It depends on what you have for a trans (manual or auto), what year the rear end is (later ones are a little stronger, but I dont know when they changed), tire size/type, and how you drive it. If you have an auto and street tires, youll be fine.

jcode68 · Feb 17, 2009

The 8" will handle that power level just fine. I replaced my open differential with a newly built True Trac or Traction Lock (I forget which is is) for $600. It was setup with 3.80:1 gearset, which was perfect for my T5 trans. I also looked into going to a 9", but the cost was significantly more unless you find a good deal in the classifieds.

zookeeper · Feb 17, 2009

I was going to go to a 9" rear, but I think I'm going to just put the money into my 8" instead. Here's a guy who sells brand-new limited slip units for $325

http://cgi.ebay.com/ebaymotors/8-Fo...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

and I already have 3.40 gears I like, so I can use them. I don't beat the crap out of my car, so I suspect it'll last a long time.

Vinyl66 · Feb 18, 2009

I am still using my 8" rear and have tons of 11 second runs on it. The automatic helps the rear end live greatly over a hard hitting stick car. Good traction bars that stop wheel hop are also a must. Wheel hop will break rear end parts.

All I have done is studded the pinion support (cheap and easy with 5 studs, hardened washers and lock nuts) and added a Detroit locker. I am also running some tame 3.55 gears which also helps keep it alive by having less torque multiplication off the line. That being said though.....I'd love to try a steeper gear and some real slicks to see what it would do

Stang_1973 · Feb 18, 2009

ballajb64 said:
yea i came up wit the same price for the unit in unlimited mustang book. How does the car feel though with the 8 inch open?

Well lets just say it gets overpowered very easily.

i was talking to a drag racer on another forum, based on a lets say 14 sec run @100 in the qtr with a 3.00 open like mine. You could take off up to .5 sec with a gear and locker swap. thats a significant difference.

calpolymustang · Feb 18, 2009

I have seen many 8" rear ends break when connected to automatics. I have one in my car and like it because compared to the 9", its lighter, takes less power to use, and is narrower than most 9"s.

What part of California are you from?

cavboy78 · Feb 18, 2009

You may also want to check this guy out. I'm in the same boat as you are and doing my research.

http://motors.shop.ebay.com/merchant/tj1141_W0QQ_ipgZ25

Buckhunter125@h · Feb 18, 2009

cavboy78 said:
You may also want to check this guy out. I'm in the same boat as you are and doing my research.

http://motors.shop.ebay.com/merchant/tj1141_W0QQ_ipgZ25

yep ............ me too .............. I've heard this guy is good !!!

phutch11 · Feb 20, 2009

Don't buy those crap LSDs from the guys on ebay. They take normal old open diffs and "convert" them to LSDs. They are junk.

Save your pennies and get yourself a TruTrac. It is the cat's ass. No maintanence, no clunking, fast lockup.

I would guess that with the power you are going to make the posi, some gears, traction bars, and some good drag radials will pick you up more like 1-1.5 seconds in the quarter when you can get traction.

Good luck...

Posted via Mobile Device

jspagna1 · Feb 20, 2009

I have a C4 and have been running 3.55's in my 8" for the last 11 years and GFG Drag Radials. No problems so far.

65ShelbyClone · Feb 20, 2009

Another option is to keep an eye out for a narrow 9" housing and get the T-Lok separately like I did. I don't think there is any more than $600 in the whole 1957 9" rear end under my '68. If you find a 28 spline T-lok and a small bearing housing, you can keep the axles and brakes from your Mustang.

doubled · Feb 21, 2009

jspagna1 said:
I have a C4 and have been running 3.55's in my 8" for the last 11 years and GFG Drag Radials. No problems so far.

How does it cruise on the freeway with your combination. What rpm are you at doing 80mph. I was wondering if I should go 3.55s or like the 3.26 in mine. Do you guys know if a 94 mustang 8.8 will bolt right into a 67? how much wider or narrower is it?

zookeeper · Feb 21, 2009

For anyone thinking of how gears might change the way their car runs at freeway speeds, check this out.

Engine RPM Calculator

jspagna1 · Feb 22, 2009

doubled said:
How does it cruise on the freeway with your combination. What rpm are you at doing 80mph. I was wondering if I should go 3.55s or like the 3.26 in mine. Do you guys know if a 94 mustang 8.8 will bolt right into a 67? how much wider or narrower is it?

At 80? Man at 70 I'm at anywhere from 3,000-3,500 RPM. I do as little highway driving as I can and you will always find me in the farthest right hand lane.
If your going to be on the highway a lot, then a 3.25 will better fit the bill.
I am not sure about a 94 8.8 fitting?? It might work. I know the Fax body rearends will work in the 67-68 body styles with some perch repositioning.

65ShelbyClone · Feb 22, 2009

The 8.8 rears are nowhere near being a direct fit, except for perhaps the elusive pre-Fox3 Granada 8.8 that I have only heard about. The axle tubes have to be modified and spring perches added.

57fairlane · Feb 25, 2009

My falcon only made 301rwhp and all it took was one launch on some old 26x10 et drags dumping the clutch at 3500 with a t5 to snap the driver's side stock axle and tear up the seals along with it.

I would at least try some mosers if you plan on racing it with slicks.

8 inch rear end

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