302/Stock Rear End

[pspeaks]

I know I ask a lot of dumb questions and this one is embarrassing.  I plan to use a Ford 8" rear end in the future but for now I'm forced to keep the 1972 MGB rear end.  The 302 is basically a stock 1979 2V motor with a four barrel and duel plane manifold; horsepower and torque should not be excessive.  With normal non-tire-burning everyday street driving can I expect the MG rear end to hold up at least temporarily or will it, as a general rule, fail quickly?

[Dan B]

Hi Paul,
My brother Jim ran a stock B diff for many years with his supercharged 215,
and a turbo before that. He wasn't gentle with it and it was still intact when I blew the motor up last year.
Dan B

[Moderator]

The MG "Salisbury" rear axle is very tough, and it will hold up fine indefinitely if you drive it reasonably gently.

[MGBV8]

No racing slicks, & no rev it up & launch it,  you'll be okay. If you're breaking loose the rear tires, you probably won't be breaking parts. A T-5 with a .63 overdrive will be very helpful.

[pspeaks]

Thanks guys, I have a T-5 SVO 5.0 Mustang transmission with a .63 overdrive that I bought from a friend (new,never been installed) for $600.00, so that area should be fine, and it has a stock NAPA clutch for a daily driver.  Well, I'm finishing the welding and grinding on the firewall today so I better get busy.  Thanks for the info and letting me know it wasn't that dumb of an idea.    "P"

[kstevusa]

Paul,  may I suggest you ck the pinion angle after you have the drive train installed.  I used the MGB R/E at first, but the u-joints did not last.  The pinion angle of the R/E was adverse and too much out of alignment.  The stock R/E took some very hard shifts and did not break.  you should be OK if the angles are close.

[BlownMGB-V8]

I'd say that for up to about 250 hp the stock axle will last pretty well. In the 300 hp range though the gears will wear faster. I abused the heck out of mine and eventually had to swap it out after it started to growl but it never broke.

JB

[pspeaks]

Thanks, I have the motor and transmission out for firewall fabrication, which we finished today; a little more grinding and it will be ready for paint.  Pinion angle is on my checklist, I'm an old airplane guy from way back so every project has to have a check list, I'll make sure it's OK.  As a T-Bucket fan I've been around some extremely big horsepower buckets that blew u-joints on a regular basis because they weren't set up right.  Thanks for reminding me.   "P"

[crashbash]

Paul
If Mr. Blackwood says it will work I'm sure it will, but I have had to replace an mgb axle on stock car from kid doing hole shots.

[TBailey]

Just wanted to say thanks for posting this question.  I found the question and comments to be very helpful.  I too am planning a 302 swap.  I just picked my project car up this week.  I am curious if one can not only use the stock rearend but also the stock front suspension and rear suspension components as well.  

Todd

[pspeaks]

You're welcomeTodd and welcome to the club; OK it isn't really a club, but it feels like one.  I ask a lot of dumb questions, but nobody makes fun of me for it.  Fitting a 302 into a pre-74 1/2 MG (1972 for me) isn't as easy as one might think but I'm told rubber bumper cars are a little less diffacult.   I'm sure any question you have can be answered;  there is a lot of smart people on this site.    "P"

[Moderator]

I am curious if one can not only use the stock rearend but also the stock front suspension and rear suspension components as well.

Welcome to the site, Todd!

You can certainly leave the front and rear suspension essentially stock. If they're in good repair, they'll serve as well as they ever did. For a Ford 302 swap, you'll most likely have to modify the MGB's front crossmember to provide oil pan clearance. Some people will argue that if you update the car's power, you really should update this or that too (e.g. brakes), but many other people complete their engine swap and then drive their car for awhile before deciding what to do about the suspension. I usually try to make one major upgrade to my car every winter: front suspension one year, rear suspension another, etc...

The later MGB axle is pretty strong... but an axle swap might give you other features / benefits:
* a more favorable rear axle ratio,
* a limited slip differential,
* brakes that are more resistant to fading or more serviceable (e.g. disc brakes),
* unsprung-weight reduction for improved ride quality, etc.
* wider track (assuming you flare your fenders),
* a different lug pattern that suits your wheel preference,
* another learning opportunity / challenge for you as a hot-rodder,
* one more thing to brag about,
* etc.

Most people who do an engine swap go to a local Dana/Spicer shop and have a prop shaft made to suit. If you change axles later, you'll probably need a second new prop shaft. You'll at least need to have the first one modified. So you probably stand to save $100-300 by doing the axle swap at the same time as the engine.  Even with junkyard parts, it'll be hard to do an axle swap for less than about $1200. (Most people spend appreciably more.)



Note: the early (through ~1965) MGB "banjo" axle isn't as strong as the later "Salisbury" axle. I wouldn't recommend a banjo axle for a Ford 302 engine swap.

[Bob in Vancouver]

Paul, I would suggest eliminating the planetary gears in the stock differential by using a limited slip or torque-biasing center section if you can justify the extra cost. Many breakages occur when one wheel spins on an open diff. and then transmits a shock load to the small planetary teeth when the spinning wheel regains grip. This can break the teeth off  and they then destroy the C/W and pinion gears. I have used a Quafe ATB for years without problems with the diff or axles and I believe there is a US-produced item that is similar in design and less costly. Cheers, Bob.

[MGBV8]

"I believe there is a US-produced item that is similar in design and less costly"

Bob,

There are quite a few of us that would be interested in knowing the name of this US item. Less costly than a Quaife would be very good.

[Bob in Vancouver]

Carl, I think the ad I saw was for the Eaton Detroit Truetrac - but I'm not sure they have a model with a flange to mate with an MG C/W or axle spline.  The price is about half of the Quaife equivalent - if the saving would cover whatever mods were needed. Cheers, Bob.