BanjoDiffRatioChange

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Page created by Dec 4th 2007:

Back to Gearboxes Transmissions and Differentials

Banjo Differential Rear Axle. The lowest hole in the front is the Oil Drain Bolt Hole which doubles as a hold the Diff Centre in place Bolt. Click to Enlargen. Photo by Ben Campbell.

Banjo Diff Ratio Change:

Banjo Centre Differences:

2.78 and 3.08 diff centres are identifiable by a bulge on the driver's side because the 2.78 - 3.08 pinion gear is larger than the pinion gear used in 3.36 - 3.89 diff centres.

Installation:

To install a 2.78 - 3.08 diff centre, you need to source the 2 long bolts used in the bulge.One bolt taps into the lowest point which is the drain bolt hole and tightens normally.To fit the other bolt, you will need to hammer out the original short stud and replace it with the other long bolt.A split pin is advisable to keep the nut from loosening. 

Coarse and Fine Spline Axles:

Coarse Spline Axles  were prone to break. Fine Spline Axles less so. I have never seen a fine spline HK-G banjo axle and I have only ever seen fine spline axles in later HZ's and WB's and in the the later LX torana's and UC's.
LJ Bathurst Xu1's had a fine spline axle's in them so Holden had the capacity to fit them back then but I have never seen them in HQ or HJ Model vehicles either.
2.78 and 3.08 banjo diffs were not common in the HQ onward series range but 3.08 were std in LC-LJ Torana's and I have seen more than the odd one of those with 2.78 diffs in them as well.
LSD's were a option so not real common but not that uncommon either.
I have even pulled a 2.78 LSD course spline from out of a rock stock std 173-trimatic equiped LH Torana.
So they were in all kinds of places not just the expected to be type cars.
Cheers Paul

Side Gears:

The Axle type must be matched to the Side Gears inside the Diff.By changing the Side Gears the Axle type can be made to match the Axles. Changing the Side Gears can easily be done by a Diff Ace.

Side Gear Swap:

side gear swap only. have done this plenty of times myself in the pits in a rush between races, often times the spare banjo centres i had were coarse, with the only set of fine spline gears in the "good" now blown up diff centre. you need to remove the crownwheel from the hemisphere so the pinion shaft can be removed. if you mark the adjuster nuts and keep everything in its place then no adjustment changes are made and it all gets put back together just fine. i agree that the coarse axles are the weak link, once upgraded to fine the centres start to fail. and i have never seen a broken fine spline banjo axle EVEREnd of submission by Ben Simpson.  
 
The closeup shows a better view of the Axle Housing stud. Note that the Stud is removed by hammering towards the rear of the Axle Housing. Click to Enlargen. Photo by HQ_SS.
 
The Image shows what the Axle Housing studs look like. Note the seration on the stud that makes it locate in the Axle housing. Click to Enlargen. Photo by HQ_SS.
 
The image shows that Axle Studs are similar to the studs used to hold the Diff centre to the Axle Housing. Click to Enlargen. Photo by HQ_SS.
Coarse and Fine Spline Spider Gears. Click to Enlargen. Photo by HQ_SS.
 
Coarse and Fine Spline Axles. Click to Enlargen. Photo by HQ_SS.
 
Banjo Diff Centre. The long stud is one way of converting from 3.36 diff support to 3.08 support. The Stud looks like an HZ 6 Exhaust/Inlet Manifold Stud. Click to Enlargen. Photo by WBUtebloke.
 
 
3.08 Banjo Diff Centre. Note the long boss at the highest point in the photo. There is also a bulge at the top right of the diff for the larger pinion. Click to Enlargen. Photo by WBUtebloke.
 
3.36 Banjo Diff Centre. Note there is no long boss. Click to Enlargen. Photo by WBUtebloke.
 
The Roll Pin has been knocked out and the Cluster Pinion is being removed. Once this has been done the Sidegears can be replaced. This job should really be done by a Diff Ace. If the Cluster Gears are too loose they will rattle when the Car travels in a straight line. Too loose and the Diff will clatter when the Car transists from forward to reverse or reverse to forward. Too tight would be dangerous. Click to Enlargen. Photo by WBUtebloke.
 
The Roll Pin lies parallel to the Axle centres as the yellow arrows indicate. Click to Enlargen. Photo by WBUtebloke.
 
3.08 and 3.36 Diff Housings. Note the long bosses on the 3.08 that use the long Bolts. Click to Enlargen. Photo by HQ_SS.
 
2.78 - 3.08 Diff Housing. Click to Enlargen. Photo by HQ_SS.
 
3.36 - 3.89 Diff Housing. Click to Enlargen. Photo by HQ_SS.
 
Banjo Diff Pinion Gears. Click to Enlargen. Photo by HQ_SS.
 
Exploded view of the Cluster Gears with Fine Spline Sidegears. Note the Shims that set the clearances. Click to Enlargen. Photo by HQ_SS.
 
One method for retaining the 3" long bolt in a 3.08 or 2.78 conversion. Click to Enlargen. Image by T.
 
The stud at the bottom left of the image has to be tapped out with a Hammer to fit a 3.08 or 2.78 Banjo Diff centre. This is because the Pinion gear on a 3.08 or 2.78 is so large it needs extra space to fit it into the center. The 2 longer Bolts used by the 3.08 and 2.78 must be fitted into the lower left hole and the lowest centre hole. Click to Enlargen. Photo by Ben Campbell.
 
The mounting studs are an interference fit into the Axle Casing and can be tapped out with relative ease. They are a similiar design to Wheel Studs. Click to Enlargen. Photo by Ben Campbell.
 
This view is looking towards the rear of the car. Click to Enlargen. Photo by Ben Campbell.
 
This stud profile is for 3.36, 3.55 and higher Ratios. The Oil Filler Plug can be seen at the rear of the Casing. Click to Enlargen. Photo by Ben Campbell.
 
  

Links:

Ben Campbell's Shed

HQ_SS' Shed

Terms:

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