MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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v8bloke
Mark Rawlins

(75 posts)

Registered:
02/02/2010 02:13PM

Main British Car:


Which rear end for 400bhp MGB
Posted by: v8bloke
Date: January 17, 2014 12:42PM

I am worried that my latest engine modifications ( TA heads for my 4.8 rover ) will be too much for the stock axle and composite springs.
Planning on a 3 link with coilover shocks and mumford link.

Have searched the net and have found conflicting views.
My requirements are simple, it needs to be strong enough for say 450bhp (one day) but at the same time as light as possible.
A well known rear end shop is suggesting that I need a 9inch to take that power. In pics the 9inch looks pretty big and would think that the rear seat/floor area will need panelling out which I don't mind as I would have to make room for the third link anyway.
Is anyone using this axle in their MG? Do I really need it? I see a light weight housing and aluminium gear case is available to help keep the weight down.

Mark


mgb260
Jim Nichols
Sequim,WA
(2461 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Which rear end for 400bhp MGB
Posted by: mgb260
Date: January 17, 2014 01:05PM

Mark, You are in England, what's available over there? In America I would recommend either the Jeep Dana 44 (perfect width) or 90-92 Ford Ranger 8.8.(Needs 1 side shortened) On the Ford I would also replace the crush washer with solid spacer and eliminate C clips by shortening axles 1" and using small 9" ends. I don't know if they are available over there.


DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: DiDueColpi
Date: January 17, 2014 01:26PM

My vote for the 9" is a huge "no".
It's a gigantic, heavy, power consuming monster.
It's only real claim to fame is that the neanderthals can't break it.
If you put one in you can never say the word "handling" again.
And say goodbye to 25 of your hard earned 450 hp.
Most R&Ps 8" or bigger can handle roughly 400ftlbs of torque.
(Torque is the yardstick that you need to use)
In such a light car as the MG getting that much power to the ground is a real challenge.
So an 8" is a realistic choice as long as a limited slip is installed.
Having said that.
I would probably lean towards a GM 8.5" rear end with a limited slip.
Just to have a little margin for error (drag racing).
Lots of choice (S10, Blazer, rear wheel sedans etc.) and lots of gear ratios available.
Some came with disc brakes as well.
Hope that helps.
Cheers
Fred


Moderator
Curtis Jacobson
Portland Oregon
(4576 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: Moderator
Date: January 17, 2014 01:44PM

Are you willing and able to consider purpose built racing axles, like this one? [www.1speedway.com]

http://www.1speedway.com/Images/Quick%20Changes/8100-c-1.jpg

One can be seen in Phil's MG here.

http://www.britishracecar.com/PhilLeonard-MG-RV8/PhilLeonard-MG-RV8-DR.jpg


v8bloke
Mark Rawlins

(75 posts)

Registered:
02/02/2010 02:13PM

Main British Car:


Re: Which rear end for 400bhp MGB
Posted by: v8bloke
Date: January 17, 2014 02:17PM

Thanks for your replies.
The only axle that I can think of over here is the Atlas which is ridiculously expensive and not a lot stronger than what I have now.
I was originally planning on a Currie 8" with ally gear case but they advised against it as not strong enough.
Love the racing axle but not much helpful info on their site, but have emailed them for more info.
Maybe an 8.8 ford is the way to go but would prefer one from a mustang rather than an explorer as the tube size is smaller.
Can only find one mustang axle for sale over here from an 84 car listed at £800 or $1300+. That's a lot for a worn out axle that needs chopping.
Which are the best rear end companies. tried Moser but didn't get a reply, Currie enterprises want to sell me a 9 inch.
Need to get this sorted

Thanks
mark



Edited 1 time(s). Last edit at 01/17/2014 02:36PM by v8bloke.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: BlownMGB-V8
Date: January 17, 2014 02:56PM

That 8.8 is also big and heavy. Several considerations:
-Strength is dependent on ring gear size. OEM MGB is 7-7/8", good for about 300hp/300tq max.
-An 8-1/2" is good for 500/500. (You don't need 8.8 or 9")
-As ring size goes up, weight and bulk increase exponentially.
-A Salisbury type is always going to be heavier than a Banjo type. Alloy hogsheads are available for many Banjos. Banjo housings should be internally gusseted if used near their limits.

The ideal solution? An internally gusseted 8-3/8 to 8-1/2" banjo axle with an alloy hogshead that used a shallow helix angle for greater efficiency. (Both the 8 and 9" ford axles use a deep helix angle and give up about 5% efficiency). But I don't know who made one. I don't doubt that it exists. There may be one in a European or Japanese car or truck. In metric that would be a 215 mm ring gear.

In terms of a Salisbury axle, the Dana44 is probably the best choice, followed closely by the 10 bolt Chevy. Both had an 8-1/2" ring gear, both are very suitable in terms of strength, weight, bulk, availability and price plus availability and price of components, gear sets, and carriers (posi).

Jim


mgb260
Jim Nichols
Sequim,WA
(2461 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Which rear end for 400bhp MGB
Posted by: mgb260
Date: January 17, 2014 04:14PM

8 3/4" Mopar banjo is the best, but don't know if you can find one in England.

[www.moserengineering.com]

[www.moparmusclemagazine.com]



Edited 2 time(s). Last edit at 01/17/2014 04:24PM by mgb260.



mgb260
Jim Nichols
Sequim,WA
(2461 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Which rear end for 400bhp MGB
Posted by: mgb260
Date: January 17, 2014 09:51PM

Mark, After some research, the Land Rover series III and V8 up to 2003 have the Salisbury(Dana 44). The 90 has a 4 pinion clutch type posi like the American Power-Lock. Same inner parts as Jag. Axles are offset and you may luck out and only have to narrow one side with another short axle. You want the one with the 640mm short axle. You will have to redrill wheel lug pattern. 95-2002 have 3.54 gear ratios in coil sprung vehicles, I don't know what others are available but Jag and Dana 44 will swap with the right bolts or tubing spacers. Will have to look at the rear axles stateside for MGB's. May be different. Look for this rear cover shape:
$T2eC16JHJH0FG0-d1!4TBSVB0r0TYw~~60_58.jpg
$_12.jpg



Edited 5 time(s). Last edit at 01/18/2014 05:53AM by mgb260.


v8bloke
Mark Rawlins

(75 posts)

Registered:
02/02/2010 02:13PM

Main British Car:


Re: Which rear end for 400bhp MGB
Posted by: v8bloke
Date: January 18, 2014 08:09AM

Thankls all,
This is so difficult as I don't want to make a mistake in choosing which way to go.
I like the look of the speedway rear end but they haven't replied to my email yet so hopefully will hear soon.
Really would have liked the ford 8inch with ally gearcase but is it strong enough?
The car is used mainly for track days so no hard launches and will never see the drag strip.
The land rover rear end looks interesting but am concerned about parts inter changeabilty. Really need a 3.25:1 or higher ratio,

Mark


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: MGBV8
Date: January 18, 2014 09:54AM

Hmm, wonder what that Land Rover rear weighs. Looks heavy. The 8 3/4 MOPAR is my fav for hodrods, but they are getting hard to find. Used to be plentiful & cheap.


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: BlownMGB-V8
Date: January 18, 2014 12:22PM

I wonder what the weight of the Mopar 8-3/4" is compared to the Dana44 or the Chevy 10 bolt. Neither will be as light as an 8" Ford of course but will be more efficient. The 8" has much stronger axles and spider gears than the MG axle but the ring and pinion is no better. Many have used them in higher horsepower applications but it is taking a chance, and in any event internal reinforcements of the hogshead flange would be absolutely essential in your application. Drag racers flogging the identically designed 9" found that flexing under hard launches changed the backlash causing greatly accelerated wear to the point where sometimes a set of gears would be shot after a dozen passes. That's 2-1/2 miles of hard use. Of course YMMV.

During the era that the MGB was manufactured, especially the Mark I and the MGA as well, it is reasonable to think that a larger sedan, perhaps some contemporary of Jaguar who was using the Dana hogshead but in the size you are looking for, might have used a larger version of the early MGB banjo axle. It is highly unlikely that any British car of the era used something like the 9" Ford, Dana 60 or 12" Chevy axle other than in a truck application but very reasonable to think they would use something a little heavier than the MGB used. What axle was in the Rover 3500 for instance? Wasn't that a Dana 44? Finding who manufactured the MGB Banjo axle would be a good first step. (Original application was a lorry? Or was that just the Salisbury?) Once you know who made it, finding what larger sizes they made and what vehicles they were used in should not be very difficult, especially if the company is still around. You could contact them directly. The design of that axle was really quite good, just what we are looking for in fact. An excellent balance of weight and strength and they are still very popular in racing even today. There is little doubt that the handling and ride of the car suffered with the upgrade to the Salisbury.

But one of the heavier/somewhat more powerful cars of the 50's/60's is bound to have this axle. And there are still a few old timers around who will remember it. Go up a class or two in racing cars and doubtless you will run across it. Very likely it is still to be found on the historic racing circuit.

Jim


NCtim
Tim Shumbera
Western North Carolina
(239 posts)

Registered:
01/19/2012 04:35PM

Main British Car:


Re: Which rear end for 400bhp MGB
Posted by: NCtim
Date: January 18, 2014 02:11PM

Why not a Jag E-Type rear end. I hear they're amazingly easy to fit on the MGB.

Tim


v8bloke
Mark Rawlins

(75 posts)

Registered:
02/02/2010 02:13PM

Main British Car:


Re: Which rear end for 400bhp MGB
Posted by: v8bloke
Date: January 18, 2014 03:31PM

Tim
I have spent many years trying to get the handling as good as possible. I think the E type rear end will be way too heavy and im not convinced that the handling would suffer.
this is how my car goes,

[www.youtube.com]

I want to keep the nimble handling characteristics. I have seen many Jag rear end conversions but never one that performs on track.

Jim
There are not many large powerful cars over here with a live axle. The SD1 isn't much stronger than the B axle looking at the shaft diameters.

Cheers

mark


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: MGBV8
Date: January 18, 2014 07:30PM

Yeehaw, that some great driving!


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: BlownMGB-V8
Date: January 20, 2014 11:14AM

>Why not a Jag E-Type rear end.

Because unless you fully flare the fenders to an extra 3" per side you cannot get the uprights and knuckles outboard of the frame rails. If you do not get the knuckles outboard of the frame rails you either reduce suspension travel, increase ride height or both, and if you do that the car will not handle any better or even as well as with a solid axle, though the ride may be a little better in some ways. Plus, you add weight and though it is sprung weight, if you do not need it to counterbalance a heavier, more powerful engine up front it shifts the car's CG rearward, away from the ideal balance it originally has.

Now, if you *do* flare the fenders out a full 3" per side, you can run up to 315 rubber on the rear and have up to a full 8" of rear suspension travel, the results being much better road holding with a more compliant suspension (MUCH better ride), a wider stance for flatter cornering, and more grip for acceleration. Plus you can accommodate another hundred pounds in the engine compartment and keep the weight balance in check. But you can't do that with the E-type suspension, it is too narrow. Use XJ-6.

Jim



DiDueColpi
Fred Key
West coast - Canada
(1365 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: DiDueColpi
Date: January 20, 2014 01:17PM

I'm still "all in" for an 8" rear end.
Particularly for a track car.
Unsprung weight is the concern here and the 8" is the lightest reasonable option.
It isn't going to be indestructible like a larger diff. But it will handle better. And it will live a long happy life if maintained well.
Have the axle tubes bent at the carrier end to give you some positive camber and away you go.
Cheers
Fred


v8bloke
Mark Rawlins

(75 posts)

Registered:
02/02/2010 02:13PM

Main British Car:


Re: Which rear end for 400bhp MGB
Posted by: v8bloke
Date: January 21, 2014 09:47AM

Yes I really like the look of the 8"! The drive shafts are 28 spline so stronger than the MG 21 spline shafts.
The weakness with the MG axle is the shafts but the diff itself holds up well. Is the 8" diff as strong as the MG axle?

Just taken out my half shafts and yes there are signs that the splines are starting to twist.

Its a shame that speedway didn't bother to get back to me.

Mark


BlownMGB-V8
Jim Blackwood
9406 Gunpowder Rd., Florence, KY 41042
(6468 posts)

Registered:
10/23/2007 12:59PM

Main British Car:
1971 MGB Blown,Injected,Intercooled Buick 340/AA80E/JagIRS

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: BlownMGB-V8
Date: January 21, 2014 02:05PM

The MG axle is weak in the shafts and the spider gears. About the same as the Ford 8" in the ring & pinion. But I personally have destroyed a stock MG R&P with a blown 215 and would be hesitant to push either it or the 8" much beyond 300/300.

Jim


MGBV8
Carl Floyd
Kingsport, TN
(4511 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
1979 MGB Buick 215

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: MGBV8
Date: January 21, 2014 03:45PM

From allfordmustangs.com

Quote:
The 8-inch rear end came out in 1962 [1962-1980]. The 8-inch 3rd members from '62-'66 are the weakest versions. Starting in '67-up, the 8-inch 3rd member case was revised [C7OW casting] to include more vertical and cross-webbing on the face of the case to strengthen it.
There are claims of people running these 8-inch rears with 400 hp, and they may be getting away with it, but these rear ends were not engineered to reliably handle that much power and torque --at least not without a lot of beefing up with [expensive] aftermarket parts.

All early V-8 Mustangs came with 8-inch rears except for the HiPo 289s --they came with 9-inch rears. The HiPo 289s were rated at 271 hp [Shelby 289s were rated at 306 hp].

The HiPo 289 carried over into the '67 model Mustangs. Even though the 8-inch 3rd member case had been revised by '67, Ford still did not use the revised 8-inch in the HiPo 289 Mustangs --they used the 9-inch.

Manual transmissions and sticky tires with lots of traction are not the only things that will kill an 8-inch. Most Mustangs suffer from wheel-hop, and this can also kill an 8-inch, even with regular street tires.

There are a few common failure points for an 8-inch; one is in the area of the input driving pinion support on the front of the 3rd member casting. The other is in the area of the pinion [spider] gears inside the differential, or with the differential main caps/bolts.

An example of a driving pinion support failure on an 8-inch [revised case] 3rd member:

[img387.imageshack.us]


An example of the main caps and main cap bolts breaking that lead to this disaster on this 8-inch [revised case] 3rd member:

1. [img387.imageshack.us]

2. [img383.imageshack.us]

3. [img362.imageshack.us]

4. [img387.imageshack.us]

I suspect the reason why so many people run 8-inch rears, in applications it wasn't really designed to reliably handle, is because a [wrecking yard] 8-inch is much easier to find in the right width for an early Mustang than a 9-inch of like parameters. It's your car and your money, so only you can make the decision of running a rear end that might last, or to run one that will give you no worries.

An 8-inch, beefed up with expensive aftermarket parts, is only as strong as your base-model, stock-configured, run-of-the-mill wrecking yard 9-inch rear.

8-inch rear ends only came with differentials that had 2 pinion gears inside. A 9-inch could have either a 2-pinion differential, or a much stronger 4-pinion differential to distribute the force over a greater surface area.


From forums.mustangandfords.com

Quote:
My point though the article didn't address any of the issues with an 8 inch. People give up on it so quickly. There is a way to help the 8" fix the pinion spitting issue. (1 of the 4 main ways an 8 inch dies). By tapping the 5 pinion support bolts further down (by about 5/8"), longer grade 8 bolts, adding a Currie enterprises heavy duty pinion support and extra large bearing that goes with it helps that issue. I haven't heard any pinions being spit out after that upgrade.
With aftermarket axles and tapping the main cap bolts further (down to 2.5 - 3 inches) and even upgrading to 1/2 bolts using caps from Currie, you really raise the strength of the 8 inch to something that fixes the other 2 main reasons why an 8 inch goes. Main cap spread and axle spline twisting. Getting a closed diff also helps spread that torque over the axles as well, help the twist issue.

Get the wheel hop out of the rear end suspension and your pinion teeth will probably become less of an issue.

What you cant fix is the inner pinion support without going to either a Currie Alumin8 or up to a 9 inch rear. From what I have seen, once you upgrade to a better pinion support on the front, the inner pinion support becomes less of an issue.

BTW I have built my 8" this way. Currie heavy duty pinion support, heavy duty pinion support bearings, 4.11 gears (not Richmond though), tapped pinion support and main cap bolts.


Ford 8" & 9" spotter's info:

[www.kevinstang.com]



Edited 2 time(s). Last edit at 01/21/2014 03:58PM by MGBV8.


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(1165 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Which rear end for 400bhp MGB
Posted by: ex-tyke
Date: January 21, 2014 05:28PM

Thanks Carl......this reinforces the fact that my choice of the 8.8 Ford wasn't flawed.
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