Salisbury rear end HP limit

lippy · #1 (**permalink**) 03-07-2013, 09:04 PM

I'm settling on my final engine options for my Cobra, and the power range will probably fall in between 600-650HP. The car is an ERA 427 and it has the standard Salisbury LSD rear end with inboard brakes, 0.82 TKO600, 3.54 rear, and I'll be using Avon tires. ERA tells me it's probably fine with 600 HP as long as I don't drive like an a**hole, and it may take up to 650 HP. But at that point and beyond, I should go to the 31 spline half shafts, etc. I won't be tracking this car (maybe very occasionally), and while I will get on it sometimes, I won't beat on it.

So my questions are: how much power have folks put through a "standard" Salisbury LSD rear end with no problem? Has anyone had failures, and if so, under what conditions and using how much HP? Thanks.

RICK LAKE · #2 (**permalink**) 03-08-2013, 04:24 AM

Lippy It's the torque load that can cause a jag rearend to break no how much HP you are pushing. I used all better parts for my Jag rearend from CWI. Better Locker, 30 spline chrome moly stub axles, rear cover cap support cover the differential carrier caps to stop walking.
Alot depends on what tires you are running? BFG on the car, you will not hurt a thing. Nitto N5 in a 315 size, will put a load on the drive train more than BFG's. I would tell you to have the rearend built with 30 spline setup with cover and catch tank and not to worry. Avons are a good sticky tire when hot. Over built the car. This will give you piece of mind when playing. Other side note, 3.54 is alot of gearing for a 600HP motor. You didn't give the first gear ratio but if it's in the high 2.70 and up, you will never use 1st gear. Drop the gear ratio to 3.31 or 3.07 for all around better driving. I run 3.31 and the car hauls hard. Rick L.

blykins · #3 (**permalink**) 03-08-2013, 05:43 AM

If you have a choice on upgrading, upgrade. Rick is right, I would over-build the car here, then you don't have to worry.

The 3.54 is a good gear, especially if you opt for the peakier engine that you've been mulling over.

Mdman352 · #4 (**permalink**) 03-08-2013, 07:25 AM

The Jag rear was used with a 230 horsepower motor and a 700 series tire which worked ok. When you use more horsepower and torque issues abound, regardless of strengthening. Don't ask me how I know this. The half shaft twisted with Avons and a off idle launch.

lippy · #5 (**permalink**) 03-08-2013, 09:47 AM

How much power and torque are these cars putting out?

CHANMADD · #6 (**permalink**) 03-08-2013, 10:31 AM

The stock Jag stuff that is in my car , since 1989, has never given a problem. I currently have a 2.88 lsd, with stock S type axles, ie solid not tubular like the above pic. My motor is super strong and I have driven the car fairly hard. I do not "drop" the clutch but am aware of cars parts when driving. Also I think the most important thing is to control the longitudinal movement of the wheel by having good track rods. Many Cobra,s rear wheels will" shudder" back and forth.....that's what breaks the parts..........

lippy · #7 (**permalink**) 03-08-2013, 11:00 AM

Quote:

Originally Posted by CHANMADD

The stock Jag stuff that is in my car , since 1989, has never given a problem. I currently have a 2.88 lsd, with stock S type axles, ie solid not tubular like the above pic. My motor is super strong and I have driven the car fairly hard. I do not "drop" the clutch but am aware of cars parts when driving. Also I think the most important thing is to control the longitudinal movement of the wheel by having good track rods. Many Cobra,s rear wheels will" shudder" back and forth.....that's what breaks the parts..........

Thanks. When you say the motor is super strong, could you please give me an idea of the power/torque?

dcdoug · #8 (**permalink**) 03-08-2013, 11:32 AM

This thread is "kinda" long, but relevant. I don't make over 500HP and on Billboards I broke a stub axle (granted it was at the drag strip

). But that was WITH 31 spine axles.

I think the axle material they used was too soft (DCEL was going to test the metallurgy but then moved to a new company, so that's on temp hold, but I'll report back when I get it tested). Another guy with a 289 ERA broke a stub axle the same weekend.

Upgrade to 31 spline chrome moly for the peace of mind. You will probably do more spirited driving than you think and its easier to upgrade now than replace them later. Removing the diff was a real PITA. To me this is one of those no-brainer upgrades.

Need help diagnosing a clutch/tranny problem

EDIT: added the link

CHANMADD · #9 (**permalink**) 03-08-2013, 10:24 PM

Quote:

Originally Posted by lippy

Thanks. When you say the motor is super strong, could you please give me an idea of the power/torque?

It has never been on a dyno.............400 small block Chevy, Solid roller with rev kit Edelbrock heads 800 spreadbore double pumper and a lot of other stuff ..........at least 500 hp/500 torque.......also the rear tyres are 255 so they spin before the mechanics break.....

Cobra #3170 · #10 (**permalink**) 03-08-2013, 11:29 PM

Quote:

Originally Posted by lippy

I'm settling on my final engine options for my Cobra, and the power range will probably fall in between 600-650HP. The car is an ERA 427 and it has the standard Salisbury LSD rear end with inboard brakes, 0.82 TKO600, 3.54 rear, and I'll be using Avon tires. ERA tells me it's probably fine with 600 HP as long as I don't drive like an a**hole, and it may take up to 650 HP. But at that point and beyond, I should go to the 31 spline half shafts, etc. I won't be tracking this car (maybe very occasionally), and while I will get on it sometimes, I won't beat on it.

So my questions are: how much power have folks put through a "standard" Salisbury LSD rear end with no problem? Has anyone had failures, and if so, under what conditions and using how much HP? Thanks.

I have been running various Salisbury diffs for years with minimal problems. I have broken several stub shafts but they were the original 10 spline Cobra and later 19 spline Jag units I have only broken 1 ring and pinion and that was this year at the Laguna Seca 50th anniversary Cobra race. The gears are very durable and if you get 30 or 31 spline stubs you will have no issues.
Ratio's were 3.31,3.54,3.90,4.10 the 3.31 was the easiest to drive because of
less wheel spin at lower speeds.
As Rick said, make sure your car doesn't chatter because that will break most anything. I run Hoosier 335x30x18 A6 tires and they hook pretty well.
Flywheel HP 806 @7500 Torque 652 lb/ft @ 5500, 594 lb/ft @ 4000 probably around 500 lb/ft @3000 so the Diff isn't getting much of a break at low rpm.

joyridin' · #11 (**permalink**) 03-09-2013, 06:44 AM

I never broke a stub or an axle, but I have blown out the spider gears on the LSD.

DonC · #12 (**permalink**) 03-09-2013, 08:03 AM

Once you get the diff. figured out don't ignore the potential problem of wheel hop with the standard rear suspension. Not a problem with the ERA outboard brake set up but a potential with the standard setup.
Here's a link to some discussion on the subject.
ERA wheelhop

DonC

Mike Bontoft · #13 (**permalink**) 03-13-2013, 11:30 PM

Mark Williams machined all of my HD stub axles, They are expensive but the best. We even had them machine 19 spline axles and I don't remember ever breaking one on a Cobra. We did have some applications that could break them but it was never on the spline. They would shear off at the threaded portion, we fixed this by eliminating the threads and using sweat on collars.
The next weakest link then becomes the outer stub shaft.
The later Powerlocks, 30 spline, one piece side gears, metric/LH case bolts were the ticket but became very hard to source. The Auburn Pro 30 spline worked well with the correct additive. Main case needs to be ground on some.
Mike