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Re: Changing Rear End Ratio in a TD

To: JVK52TD@aol.com
Subject: Re: Changing Rear End Ratio in a TD
From: Curtis Cook <ccook@admin.coloradocollege.edu>
Date: Tue, 24 Aug 1999 12:45:24 -0600 (MDT)
Same here, in a TF-1500.  And the XPEG sounds as though it is thrashing
along at 5500 when I attempt to stay out of the way of the semis.  -Curtis

On Sun, 22 Aug 1999 JVK52TD@aol.com wrote:

> Greetings All,
> 
> I have been following the thread on the changing of the "T" rear end.  How 
> fast are you driving with this change ??  I have had trouble with the engine 
> not standing up to 65-70 mph speeds with the 4.3, even though it will go much 
> faster than that !!!  I am at 5000 when I am @ 65 & 5500 @ 70..  Do not know 
> how accurate my tach is....
> 
> John Kinney    Danville IL
> 
> 
> In a message dated 8/9/99 6:38:28 PM Central Daylight Time, 
> lpalmer@vanstar.com writes:
> 
> << Bob,
>  
>  See my answers below:
>  
>  -----Original Message-----
>  From: BobMGT@aol.com [mailto:BobMGT@aol.com]
>  Sent: Monday, August 09, 1999 5:07 PM
>  To: mg-t@autox.team.net
>  Cc: mgs@autox.team.net
>  Subject: Changing Rear End Ratio in a TD
>  
>  
>  I've always shied away from highway driving in my TD. The engine just
>  doesn't 
>  sound too happy at 4000rpm. I've finely decided to take the plunge and
>  change 
>  the rear end ratio. My mechanic has an MGA parts car, and is ready to sell
>  me 
>  any parts I need from the rear end. Are the ring and pinion gears the only 
>  two parts I'll need from the MGA? 
>  
>  No. If you choose to use MGA ring and pinion, you'll also need the driving
>  flange, the pinion distance tube and spacer. Bearings for at least the
>  pinion will also be required. But it's better to buy those new. Optionally,
>  as long as you are in there, you'll probably want to replace the carrier
>  bearings if they aren't brand new. (By the way, I have a full set of
>  bearings for sale, if you need them.)
>  ==================================
>  Also, what is the recommended ratio for highway driving? Here are the
>  options 
>  I've found:
>  
>      Standard TD 5.125   3900rpm @ 55mph (What I have now)
>      TD option       4.875   3700rpm @ 55mph
>      TD option           4.555   3470rpm @ 55mph (Gears available from Moss)
>      MGA             4.3     3300rpm @ 55mph
>      MGA             4.1     3120rpm @ 55mph
>  
>  It depends upon the type of driving you do. If all you do is freeway driving
>  across nice flat states, the 4.3 is good. If, like me, you do a bit more
>  hills, I find the 4.55 ideal. Don't consider anything lower ratio than 4.3.
>  Since the TD transmission gearing is different than an MGA, don't expect
>  that you'll get the same RPM/Speed combinations as the MGA. I find that with
>  a 4.55 rear end, I do just about 60 MPH at 4000 RPM. I can also happily do
>  65 MPH, at about 4250 - 4300 RPM. All this with a slight reduction in hill
>  climbing ability. I know find, with a 4.55 ratio, that hills I used to take
>  in 4th gear, now require 3rd.
>  =========================
>  My mechanic claims the MGA parts car has a ratio of 4.5, but I only see 4.3 
>  and 4.1 in the literature. Is he mistaken?
>  
>  No, a 4.55 ratio was available. I know, because I'm running one in the TD.
>  
>  Carl Cedarstrand wrote a very good booklet on the subject of rear end
>  conversions some years ago. It is still available from Moss Motors. I highly
>  recommend you get a copy and read up on the theory and practice. I used it
>  as the basis of a workshop I conducted for our local club last winter. We
>  did 6 conversions in one day. To a person, everyone is very happy with the
>  4.55 ratio.
>  
>  Regards,
>  Lew Palmer
>  Bob Donahue (Still stuck in the '50s)
>  EMAIL - BOBMGT@AOL.COM
>  52 MGTD - under DIY restoration NEMGTR #11470
>  71 MGB   - AMGBA #96-12029, NAMGBR #7-3336
>  
>   >>
> 


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