[Staowners] my rear end - need to change it - HELP!

[Henry Gillard]

Ray

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

 

 

 

 

 

 

 

 

 

 

 
Maybe I'm only half awake (it's not yet 7  in the morning) but I can't quite see what you are trying to achieve.                                                                                                                                                                                                                   

If you can't get any useful performance in fifth, ie as soon as you come to a hill the engine starts to labour - forcing you to change down, then using a lower rear axle ratio may not really help you in practice.
eg
existing fourth is (say)  1.00:1    and differential is 3.89:1   Effective gearing is 3.89:1                                                                                                                                                                                                                                                       
fifth is (say) 1.16:1 and differential is 4.50:1   Effective gearing is still going to be 3.89 to 1
                                                                                                                                                                                                             
What will happen is that the effective gearing in all the intermediate ranges will fall by about 16%  (ie 4.50 / 3.89)                                      
That will mean you should get more spritely acceleration through the gears, but you'll have to use five instead of four.
 
The potential downside is that with the new differential gearing, you may find that the "right" gear for a 
given speed is no longer what it was before.  
 
eg if the speed limit is 30 mph, then before maybe you drove in 3rd happily: you may now find that third is too high (engine is reving too high to be comfortable) and fourth is now too low.                                                                                                                                                     
 
You could work out what it is going to be like by driving 16% faster under certain conditions and seeing if you are happy with the engine revs
                                                                                                                                                                                      
If your problem is indeed that when you come to a hill in fifth the engine starts to labour - forcing you to change down - then I suspect that what you really need is not a change of gearing, but a more powerful engine
                                                                           
Sorry to pour water on your plan, but I'd hate to see you go to the expense of changinging the diff to find that you're no better off and maybe worse off.           
 
HMG                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
 


From: raymead at comcast.netTo: staowners at sunbeamtalbot.infoDate: Sun, 7 Oct 2007 17:42:23 +0000Subject: [Staowners] my rear end - need to change it - HELP!
Hello all,
 
As most of you know, my '54 Alpine has a 1984 Toyota 22R
engine and 5 speed transmission in it.
 
It has the original 1954 Alpine rear end.
 
Because of the gearing of the rear end, I rarely get into 5th
gear with this engine/transmission set up...............
 
So, was thinking that I need a lower set of gears in the rear end.
 
Being mechanically challanged, I will, of course, have someone else
do this - BUT, the real challenge I suspect is figuring out what set
of lower gears would fit and what car/year they would be from............
 
Can anyone out there answer this?
 
tks, ray
'54 Sunbeam Alpine
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