109 Front diff now 4.71

Well, at least this afternoon’s work went a little better than yesterday’s, with no running around trying to find special tools in a hurry.  Both diffs are now 4.71 to reduce the strain on the gear box and to give better low speed driving.


I wish I had stuck to the original ratios when I did the axle swap, but hindsight is always 20/20.  Top speed wasn’t increased at all with the taller diffs, though the maximum comfortable cruise speed was increased from 60 mph to a little over 65 with the drop in engine rpm.  Even so, the road and wind noise make 70mph uncomfortable for long periods.  Mpg will take a hit, going back down to 27mpg from the 30mpg with the diffs, but the cost of rebuilding the gearbox is greater than that saving in fuel and the inconvenience in refuelling slightly more often less than the inconvenience of removing the transmission a couple of times a year!  It’ll be nice to get a good low first gear for pulling away, as it has been similar to setting of in second with standard ratios, which must be hell on the clutch.  Cruising at 30mph in town will be back to low rpm in fourth rather than mid revs in third, so will be more efficient for town driving as well as easier and better for the transmission.  So, the next job is to remove and rebuild the gear box – at least I know the bolts will all come undone without trouble, given how short a time it has been since it was last out.

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  1. Fingers crossed that you don’t have any more gearbox problems. I hate removing the gearboxes on Series trucks so I can imagine how frustrating this has been for you.

  2. That frustration is compounded by the constant reminder that Marsland screwed up the chassis by galvanising it with the detatchable cross member in place, welding it in. Thanks for the sympathy, though, Ian!

  3. I too feel your pain Nick, there’s nothing like removing the complete insides of the cab to get the gearbox out. Luckily Marsland didn’t galvanise my chassis with the gearbox crossmember in situ so at least my gearbox comes out the bottom as nature intended.

    Glad you have got both diffs swapped over.



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