My '76 B daily-driver has o/d as does my temporarily-out-of-service '73 GT,
but the car that does all the really long trips is my '73 without o/d. I
have an o/d box for it, and one of these years it will go in. My
experience is that o/d makes no measurable difference in gas mileage - and
so far I haven't noticed any differences in engine wear. O/D does make a
HUGE difference in driver fatigue. Like Tab, I can't stand the endless
hours of high revving. About 3300 is the limit of my tolerance - maybe
3500 for a few hours. The result is that I just barely drive the '73 fast
enough to keep from getting rear-ended on the interstates (which I drive
only when a suitable "blue highway" can't be found) - about 60-65 mph. I
get 30-34 mpg and never a speeding ticket! In the '76 I easily cruise with
interstate traffic at 70-75 mph and when the flow goes faster than that
I've caught myself unknowingly drifting up close to 80. Because I'm
driving faster, my gas mileage is not AS good: 26-30 mpg. I do love the
o/d but only for my own comfort. I know of no reason to swap a good
Laycock o/d tranny for a 5-speed. The Laycock is very reliable - the only
problem I've ever had was due to worn 'O' rings on the solonoid - about a
$2 very-easy repair.
Allen
>Date: Tue, 23 Nov 1999 13:56:05 -0500
>To: mgs@autox.team.net
>From: Tab Julius <tab@penworks.com>
>Subject: High RPMs bad?
>
>I've been watching the OD discussions, plus the comment from Gerardo of
>being tired of cruising at 5000 rpm (me too). Actually, anything over 3000
>RPMs I know I'm burning up the gas, but I just can't feel that higher RPMs
>are very good for the engine; like the optimal is 2500 to 3000. Of course,
>going red is definitely not good, but what about 4000 to 5000? It won't
>blow the engine, but surely it's taking years off. Or is it not? On the
>back roads it's not a problem, but the 75 mph highways I feel like I'm
>doing my engine a disservice if I actually go that fast for an extended
>period of time.
>
>Wishin' it was a 5-speed...
>
>- Tab
>
>'78 B
>
******************************************
Allen H. Bachelder =iii=<
Sinking Creek Home for Wayward MGs
New Castle, VA 24127
USA
540/544-7333
******************************************
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