Fitting a non powerloc diff head
#1
Fitting a non powerloc diff head
Not really an expert on diff's - so just asking this question
Looking to put a 3.54 (or there abouts) diff into my '82 V12 XJS and i'm not sure about the powerloc diff head availability in New Zealand
If another jaguar diff could be found of a similar ratio - that wasn't a powerloc version - would that fit?
Alternatively - can the gears be swapped into the powerloc assembly??
Excuse my ignorance on this
Looking to put a 3.54 (or there abouts) diff into my '82 V12 XJS and i'm not sure about the powerloc diff head availability in New Zealand
If another jaguar diff could be found of a similar ratio - that wasn't a powerloc version - would that fit?
Alternatively - can the gears be swapped into the powerloc assembly??
Excuse my ignorance on this
#2
Here a few ideas....
Find a diff from a 90's 6 cylinder xjs. That should have a 3:54 and would be low bias power lock and would probably not need a rebuild but that ratio is a bit short for a XJS with a 3 speed auto and the low bias power lock is basically useless with the power of the V12.
Find a 3:31 early XJS or XJ6 series 2 non-powerlock. Then you can retrofit a commonly available 19 Spline Auburn locker carrier. An early diff will certainly need a rebuild, and rebuilding it with the Auburn locker and Dana 44 side bearing will cost way less then using all the OE jag bits. The Auburn locker is also newer and better locker technology. There are a few considerations with the setup but if you have a working 3:31 to start with you can make some precision measurements and have the new diff arrangement setup quickly.
http://www.summitracing.com/parts/aub-5420112
I've done both of these so I know this first hand.
Last edited by icsamerica; 07-30-2014 at 01:23 PM.
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Doug (07-29-2014)
#3
Thanks for the comprehensive reply
Really interesting what you were saying on the fitment of the 'low bias' 3.54 diff - and how this doesn't really work in the V12
Seems to be a pretty standard response that this is the one to use from other items I've read. Can the 'low bais' be adjusted I these heads??
Thanks again for your time on this
Really interesting what you were saying on the fitment of the 'low bias' 3.54 diff - and how this doesn't really work in the V12
Seems to be a pretty standard response that this is the one to use from other items I've read. Can the 'low bais' be adjusted I these heads??
Thanks again for your time on this
#4
See page 3 of this document on the matter. I've had a few of these low bias units and it seems like the bias it so low its basically useless out on the road. Seems like Jag engineers got it wrong and made the bias too low and came up this cackamamy "refinement" excuse to address the owners complaints.
http://www.terrysjag.com/XJS%204.0%2...%20Service.pdf
At this point I explored retrofitting an earier high bias unit and determined it was easier far more economical to replace it with the more modern Auburn un
Also 3:54 is not ideal or a 3 speed auto car. It will be high revving on the highway. My car has a SBC and 700R4 over drive 4 speed transmission so 3:54 was perfect.
No adjustment is possible but anything could be re-engineered given enough time and money. Life is short and funds should always be allocated efficiently so its advisable to drop in a more modern race and trace proven Auburn unit.
Last edited by icsamerica; 08-03-2014 at 03:11 PM.
#5
That's more great information - thank you
So reading between the lines the 'inboard' brake unit with a 3.54 was a higher bias unit - and the outer brake unit was a lower bias setup
I'm also likely to swap to a 4 speed auto or 5 speed manual - so the 3.54 unit is still the one i'll likely go with
The Auburn unit sound ideal however for a rebuild - so i'll track one of those down as well
So reading between the lines the 'inboard' brake unit with a 3.54 was a higher bias unit - and the outer brake unit was a lower bias setup
I'm also likely to swap to a 4 speed auto or 5 speed manual - so the 3.54 unit is still the one i'll likely go with
The Auburn unit sound ideal however for a rebuild - so i'll track one of those down as well
#6
Yes. It sounds like you want the vehicle to be a bit more performance oriented. You may also want to get the out board brakes. The inboards are downright ineffective compared to the outboards. They are left over from the Pre-ABS days and the system is heavily biased toward the fronts so the rear breaks don't so much actual stopping. If you switched to outboard too the stopping performance and pedal feel would be vastly improved. Working ABS is a must to prevent the car from coming around in certain braking situations. BTW, my car is a 76 XJ coupe and the IRS from a 96 XJS convertible was a pure bolt-in except for the brake lines which had to be custom made. Early cars have a single fluid line and a T fitting for the rear brakes. Later cars have 2 individual fluid lines for the rear brakes.
That would be a worthwhile upgrade. Should have been built that way.
They are readily available and are popular in Jeep circles since the Jeep also used a Dana 44.
Last edited by icsamerica; 08-04-2014 at 04:38 PM.
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