P4 90- too short axle ratio

P4 90- too short axle ratio

Postby MisterEnderby » Sun Oct 07, 2018 9:18 am

Hello, in addition to my Wolseley 14/56 from 1936 I like to buy a Rover P4 to tow my pre-war caravan even on longer distances and on the highway.

Yesterday I made a testdrive with a 1956 P4 90- the car was in quite good order and drove fantastic, but I was confused that from 33mls/h on the engine was to be heard working, from 45 mls/h it was heard to be working very hard- I could not imagine and even would not try to get the car driving more than 60mls/h without feeling of tortouring the engine.

I am used to that standard with my prewar cars and even heared about the short axle ratio with the P4 , but expected the Rover to drive about 50 mls/h with adequate silence.

The vendor offered me a 1:3,91 diff on top for free, but before buying the car I would like to know:

-are all 90s have a freewheel fitted (in the tested car it was not engaged and I even have not seen a knob under the dashboard)?
-will a 1:3,9 diff solve my problems
-will a 1:3,54 diff maybe the better option or does it make the car too lazy
-would bying a later gearbox with overdrive without changing the diff even an option

and at last a different question:
are there aftermarket chrome bezels to put around the instuments availiable? Would like to have a bit more blig-bling on the dashboard.

Regards from german baltic sea
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Joined: Thu Aug 18, 2016 7:16 pm

Re: P4 90- too short axle ratio

Postby Phil - Nottingham » Fri Oct 19, 2018 10:44 pm

1956 models did not offer freewheel - fixed was standard with axle ratio 4.3 : 1. Overdrive was optional. The 3.9 : 1 was used on 55 models which had freewheel as standard.

I am surprised you think its over-reving and noisy as our 100 has a 4.3 : 1 rear axle and in top without overdrive engaged is quiet enough even at 70 mph

Perhaps you need to check what axle ratio you actually have by turning the wheel 2 turn (with the other wheel on the ground) and counting how many turns the prop shaft moves. It may be it already has the 3.9 : 1 diff?

A box with overdrive would be better if it does have the standard diff.

Rover did not do bling really especially in the mid 1950's. No different bezels are required!
P2/P4/P5/P5B/LR's - EXJ 8**/2**8MY & others
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Phil - Nottingham
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