FE/FC Diff Ratios.

[old-blu]

 A question for the Mechanics on the Forum.  What diff ratios were used in the commercials & sedans in the FE/FC Models?  I always thought it was the same for all, ie: 3.89  I thought the 3.36 ratio was used in the EK Auto & 3.08 with the 4 speed boxes. Was a 3.55 used in commercials?  Were lower ratios used in delivery vehicles?    Cheers Kevin. 

[mcl1959]

Kevin, 3.89 for all up to and including EJ
EH to HR had a 3.55 for manual's and a 3.34 for autos.
Interestingly in the 20 year parts book they list a 3.89 option for EH to HR (section 5.529)
I don't know what this would be for.
Ken

[old-blu]

Thanks Ken. A Club Member up here has just brought home an FE Ute, which I think is revving far too much @ 50mph.  I will check out the diff housing & go from there. Maybe a faulty gear box revamp! Kevin.

[mcl1959]

Gearbox can't be put together that wrong that the gear ratios are changed!
I would think it's more likely small diameter tyres. Original crossplys were much larger diameter than modern radials
Ken

[old-blu]

 When this is sorted, I will let you know. Thanks Kevin.

[hsv-001]

3.55 and 3.36 maybe in EH -HR .

[Dr_Terry]

Correct. EH, HD & HR got 3.55 & 3.36 ratio in regular production, but there was a 3.90 option also.

This was usually seen in small engined manual commercials & taxis etc. Imagine a low compression 149 manual panel van with a bit of a load aboard attempting a hill start. This is when you need a 3.90 diff.

The 3.90 is not the same diff as the Grey motor's 3.89. The 3.90 had a 39 tooth crown wheel & a 10 tooth pinion, whereas the 3.89 tooth count was 35 to 9.

All versions of FX to EJ had the 3.89 rear axle.

Dr Terry

[Errol62]

Good info dr terry.

While we are on the subject, can you advise when the 3.08 and 2.78 ratios first appeared in the coarse spline format? They are a bolt in fitment like the other ratios and work well behind a red and trimatic as you know.
Cheers
Clay


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[Dr_Terry]

To my knowledge the first 2.78 coarse spline Banjo was seen in HK 307 Powerglides, booths had a larger yoke to suit the V8 uni joint. I think 3.08 also appeared in HK V8 also.

I think the first regular usage of 2.78 & 3.08 with 6-cyl sized uni joints were in LC/LJ Toranas.

Dr Terry

[Errol62]

Thanks, concurs with my belief.


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[old-blu]

 Finally got the "over revving" issue sorted. The ute had an extra fan fitted to the front of the radiator, which ran noisy. The diff is 3.89. Front wheel brakes were grabbing when reversing which explains why the ute struggled to get going in reverse. He thought the gear ratios were incorrect. All good now.  Kevin.