Looking for diff and brake upgrade

[wombatzj]

Have one of the Boomerang AC Cobra with Crown chassis and running gear, 351C with FMX gearbox.
Looking at changing diff centre due to ratio being to tall around 3.8 need to go down around 3.0. Have heard some Holden diff centers will fit.
Also front discs and rear drums need upgrade, would appreciate any help with these issues please.

[Rob. Smith]

Might be just easier to fit a complete new diff with brakes etc. Hoppers stoppers would be a good place for some brake info.

[Rog246]

I would probably have a look at maybe supra stuff you might find some good gear staying with Toyota...............or not

[boxhead]

What width is your diff, flange to flange?

Being a crown chassis it will run same stud pattern as Ford.
That means Toyota, Ford, Valiant stud pattern (so all these will bolt in fit your wheels)
A common swap for Valiant guys is to use a late model (EF, 3.23:1 LSD from memory) falcon diff, they are a few MM's wider than a standard Valiant diff, but you get disc brakes.
Or if you need shorter diff the Centura has correct stud pattern and is a common swap into earlier Valiants wanting the late model stud pattern.

I have a couple of Valiant 2.92:1 diffs sitting in the grass out beside my shed.

[David Hodgson]

Wombat, you are correct, most Crowns in Aus in the 70's were assembled here and following the 'local content' requirements, had Banjo diff's. These used the Holden centres and splines but Ford stud pattern, so there's plenty of ratio's available, and would be the cheapest and simplest ratio change.
Having said that, if it see's only cruising duty you should be OK, after all your current one has obviously done OK. Won't last long though if it gets much more than 'spirited' driving.

[wombatzj]

Ta guys, will look into these options and do some measurements.

[DaveW]

Hi Wombat,
I used to work for AMI / Toyota (20 years), not in the 60's or 70's but i know heaps about the the MS series crowns from that era,

The rear axle assembly is almost identicle to the EJ, EH, HD, HR, holdens, only about 5 mm difference in the track.
The axles are slightly longer, Toyota PCD and were made to suit imported brake setup initially which then changed later (early 70's) to PBR.
I believe a Holden rear assembly will bolt straight in. Rod hadfield or Hoppers Stoppers have disc brake conversion kits for converting the Holden version.
The diffs have ratios available 2.78, 3.08, 3.36, 3.55. 3.89:1 there was also LSD available in some models up to LX Torana. the spider gears are the weak link in these diffs.
Also, a guy in Traralgon Vic has a Crown Chassis Cob with an LJ complete rear axle in it.
The track is about 100mm less, which is great for the dished wheel look,
I dont know his contacts though.

Dave

[tomcat racing]

Originally Posted by wombatzj

Have one of the Boomerang AC Cobra with Crown chassis and running gear, 351C with FMX gearbox.
Looking at changing diff centre due to ratio being to tall around 3.8 need to go down around 3.0. Have heard some Holden diff centers will fit.
Also front discs and rear drums need upgrade, would appreciate any help with these issues please.

You have got that the wrong way around there, the 3.8 is a lower ratio than a 3.0. the 3.0 is the tall ratio.

[wombatzj]

Great information guys, always get my lefts and rights back to front as well.
Will keep an eye out for some diffs with the right ratio, hard part is not put the foot down at the start, why so much for cut down 9" diffs.
Regards
Wombat.