Blue motor/4 speed box/ dif into FC

[Kermit]

I have purchased a VC commodore with 3.3L blue motor and 4 speed box to put in my FC which already has HR front end. My question at this stage is re the Dif which is a 2.6 ratio. Does anyone know could I, or should I put the complete rear end from the VC incl Dif into the FC or am I better to look for a 3.36 complete dif or center.
I would appreciate any help on this
Rgds
Mick

[Vinnie]

Mick
A bit confused on the question you are asking.
Well if you have the original FC diff there is no contest, as you will probably or definately have your rear locking up all the time- can be fixed with proportioning valve.
Depends what u want the car to do. Keeping the FC rear will give you quicker take off, but in relation to speed (free way) the motor would have to give more revolutions to maintain higher speeds in top gear. In a nut shell - the lower the diff ratio the less output revolutions of the gear box, best practice is to keep all drive train the same as per matched design, but you might find that you venture into another problem of matching the brake balance.
My advice try it c how you go, as you could always fiddle around with the diff at a later date.
Hope this helps.
Vin
P.S spend some time surfing this site, as you learn things that you wouid not even think about. :-/

[mcl1959]

First - do you know how difficult it is to put a Commodore diff into the FC ?   Spring pad perches need to be welded on as well as some of the old trailing arm mounts will need to be cut off for clearance.
I think 2.6 ratio is too low for the FC even with 13 inch wheels.
The best option is to install a HR diff and find a 3.08 ratio centre (3.36 is OK as well but less fuel efficient)
You can then match brake wheel cylinders easily and it is all a bolt up conversion.
If your blue motor is going to be worked and put out some forceful horsepower then a swap to a Commodore diff may be worth while, but the diff of choice is a VL onwards Borg Warner diff which is way stronger.
Ken

[ACE]

Hi Mick,
I think the 2.6 ratio would be too high for the FC. (The lower the number the higher the ratio ).
With the motor and gearbox combination you are using my choice would be a 3.08 ratio centre in a HR housing which would be good for city and highway driving.
Regards ACE

[Kermit]

Thanks everyone for your guidance now I know which way to go
Rgds
Mick    

[robbzfc58]

hi mick   im with the other guys on this.   i have a blue 3.3 motor & 3.08 diff in a hr housing in my fc & its fine in all situations ,including towing
           cheers trev

[smithy]

mick just too add a little on what the other guys have said, in addition to removing the original spring mounts and welding on new spring pads to suit the leaf springs the diff will also need to be shortened $$$$$$$$, add to this new axles  some of the shops i spoke to before i got my diff cut will not cut down the axles for safety reasons. i had my commodore diff cut down to HR width, and new axles at the right length and spline sourced from wreckers.
after all that you then have the dilema of wheel size, 15 inch on the rear (commodore) and 13 on the front. option then is to have the rear discs re-drilled to early holden stud pattern or change the front discs over to commodore to match the rear.
i did the latter so i can now run 15in+ wheels all round (more wheel choices) using modified HR stub axles from CRS.
oops, then you also have the tailshaft to think about.

turned out to be quite an expensive learning experience fior me.
and im still not out of the woods yet, im still trying to get the handbrake right  

the up side to all this is you have 4 wheel discs, a little overkill now but i have plans to up engine size in the future, 192 now to supercharged V6, so then they will come in handy.
hope this helps
dean

[Sarge]

Mick
     I am running a 186 (warm) 5spd Celica gearbox & VN Commodore diff, Front brakes are HQ stub axles and discs. fitting the 5spd box was more trouble than the diff was. Just my two bobs worth. Handbrake well there's another tin of worms yet to be opened.

Regards
Sarge

[smithy]

hi sarge, i had to have my commodore diff cut down cause with only the standard 15in wheels and 195 tyres there was about 10 mm clearance to the outside guard, and yes the lip was rolled.
also it now brings the wheel track back to standard width. i do want to fit a wider wheel and tyre combo.

now with the handbrake, what did you do to make it work! im in the final stages of a rebuild so i'd be really interested to hear what youve done.
any help or sugestions would be greatly appreciated.
thanks
dean

[sgo]

In my case with a vp rear end and using the vp handbrake lever between the buckets it turns out that the vp cable was the right length and slotted in perfectly.

[Sarge]

Dean I had the hand brake working with the 4 spd fitted. Now that I have changed to the 5 spd I have to modifiy the hand brake cable again. I see that sgo has posted that vp fit if you mount handle in the centre so that could be a good place to start.

Regards
Sarge
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