Just pull the pumpkin out and take it to a diff shop. They ‘ll replace the bearings, fit a new collapsible spacer, seals etc and set the gears.

An original HK V8 Kingswood. Nice. There were plenty made but today you normally only find Brougham, Premier, GTS and Monaro. HK Kingswood and Belmont optioned with V8 are not common.

Note that there are cheaper options around than a Borg Warner conversion. A Volvo diff Dana30 is pretty good, right stud pattern and about 125mm or so narrower so you can run wider offset rear wheels. Lots of ratios available as its the same as Jeep.

You can also fit a VB to VB 5.0L rear axle, but it's Commodore stud pattern. Slightly narrower too than HK-HG. Even just a stock VL Borg Warner might be OK if your car is standard 307, has Commodore stud pattern again but its a much cheaper diff than a V8 one.

The other one is a 67-69 Camaro or Firebird in 10 bolt or 12 bolt. 10 bolt examples turn up cheap here on Facebook or Gumtree, just have to change the hangers and run the GM drums. Will normally be a 4.75" PCD though. All parts are available new from the USA.

Edited by user Thursday, 18 July 2024 3:21:01 PM(UTC)  | Reason: Not specified

Apart from Volvo, yes they will. If you want your wheels and hence width and stud pattern, it’ll be a custom diff.

You won't be able to use Volvo with your current wheels either, as the diff is about 60mm narrower per side. You'd be running deep dish rears. Good for when you want to fit 8" US racers or similar under the rear, but finding that sort of stuff in 4.25" PCD will be hard. So most likely custom wheels.

Volvo 240 and I think even early 740. They are a disc rear end, drum handbrake inside the disc I believe like a Commodore. I have heard that wagons had a slightly wider diff but only by 10mm or so, but that may also just be wheel track not diffs. There will be some catches though, like the hub may be too big for your wheels? I remember Dr Terry stating the brakes are OK but not fantastic.

The Volvo diff would be only if you are competent at fabrication yourself and able to save a bit, as the diffs are very cheap. You'd still need a custom tailshaft, custom handbrake cables, brake lines etc just like with a 9" or Borg Warner conversion.

It's a shame you want to keep your existing wheels, as the best way to do all this is to have a new diff made in 4.75" stud pattern that accepts either your HK drum backing plates or HQ-WB (they are different), and run HQ-WB drums. Then fit HQ-WB rotors and HQ calipers on the front. And run wheels with 4.75" PCD. You can make the diff slightly narrower (like 3/4" to 1" per side) so you can run off the shelf 7" wheels on the back easily, potentially 8".

If you are happy to run a 2.75:1 diff, a 9" can be affordable as the 2.75:1 centres are quite cheap.

What I did with my HK GTS was had Rodtech build me a new housing and 28 spline axles. It is built 3/4" narrower on each side and the housing is setup for HQ-WB backing plates. These take HK-HG handbrake cables, and will take either HK-HG drums or HQ-WB drums. The housing is built with HQ-WB commercial leaf spring perches rather than HK-HG, so you just have to use the HQ-WB lower plates and U-bolts. The standard HK-HG shocks attach to these using the HQ-WB lower bolts.

I made it 3/4" narrower each side so it will take standard 15x7 Pontiac Rallye II wheels or aftermarket versions of those or Chevelle SS396 wheels with 215/65/15 tyres, leaving the quarters dead stock. I also have 15x8 Simmons P86 wheels that fit on the rear with 225/50/15 tyres.

Fronts can be challenging with brakes bigger than HQ. Mine has BA-BF rotors and some of the 15" wheels struggle for caliper clearance. HK stubs are identical to HQ, just swapped side to side. So HQ-WB rotors bolt straight on, as do the calipers.