Which Diff to upgrade to?

**HXsman** · 13-06-2017, 04:44 PM

Hi all,

I am currently replacing my tired 253 with a 355. Everyone suggests I might need to worry about my diff. Its currently a GU4 (3.04?) behind a Trumatic.

What should I upgrade to other than a ridiculously expensive 9"

I'm not looking to race / drag or burnout (too old for that)

Just need to be sure it can withstand the 355

Appreciate your thoughts

**wbute** · 13-06-2017, 06:25 PM

Just stick with the Salisbury. If you drive to its limits you will get some miles out of it. They raced at Bathurst in an A9X with one. The alternative that's common is 9 inch.

**Sandaro** · 13-06-2017, 06:37 PM

No burnouts, then no problem requiring an upgrade

**Valencia** · 13-06-2017, 07:31 PM

Originally Posted by Sandaro

No burnouts, then no problem requiring an upgrade

Agree your diff is a 3.08

**Beachy** · 13-06-2017, 08:12 PM

How much is a 9 inch these days ?
If you put 3.00 or 3.25 9 inch in you would never look at it again

**Valencia** · 13-06-2017, 10:40 PM

Originally Posted by Beachy

How much is a 9 inch these days ?
If you put 3.00 or 3.25 9 inch in you would never look at it again

My 9 inch LSD 3.1 was installed in 1990 havnt even changed the oil ever
one thing i do know they are stronger than the keyway on a 308

**Dr Terry** · 14-06-2017, 08:05 AM

The 9-inch Ford diff is not that strong in stock form. OK, it's tougher than a 10-bolt Holden Large Salisbury, but it's not the be-all & end-all.

My B06 One-Tonner with 308 TH400, even in standard form was a bit hard on diffs back in the 80s. Yes, it was driven hard & did a lot of towing, but didn't do any burnouts. I killed 3 standard diffs, then changed to a 3.25 9-inch.

The side carrier bearings went noisy within 1 year & then the pinion seal began leaking badly, the diff guy said that this was commonplace, so I spent big $$$ having it overhauled.

Less than 18-months later it began making very strange noises so it out it came again. The 'hat' part of the centre carrier had cracked & separated, right around the outside thru the centreline of the crown wheel retaining bolts. Again this was a "common" failure so I had it upgraded with a aftermarket billet hat, the original was just cast iron. I do less mileage in it these days & it has held together. By the way, the original 28-spline axles are still in there today. The conversion involved using Holden axles & brakes with the Ford centre.

When we were drag racing, the 9-inch was the thing to have, but again all 9-inch diffs are not equal. In our Monaro we went thru 28-spline thin axles, 28-spline thick axles, 31-spline GT-HO axles, & then finally 35-spline aftermarket items (Mark Williams) & a billet one-piece spool to replace the standard LSD centre, before we stopped picking up broken diff pieces & spending money over & over again. This was a 10-sec sedan SS/A car, not far removed from a street car, it wasn't a Pro-Stocker or Door-Slammer.

Good alternatives for use in a Sandman would be an M75, M78 or M80 out of a late Holden or Falcon. More commonplace & cheaper than an overhauled 9-inch Ford unit.

Another conversion I've seen is the fitting of B-W gears & hemisphere to a standard Holden Salisbury housing. It is stronger than the original & the parts are plentiful, as some of the 10-bolt bits are getting scarce. It also looks concours original from the outside.

Dr Terry