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MG MGB GT V8 Factory Originals Technical - Does size really matter

Thank you to all who have answered my questions over the last year about my Ford 8" rear installation. On my first ride I asked a mustang driver going down the highway to tell me when he hits 60mph,when he did my car said 42mph,then he punched and took off I punched and couldn't keep up beacause I have never in three years had to downshift in the LT77 .82 fifth gear, to keep up. After just 40 miles I Love and Hate the 3.00 rear end. Now my only option I would of considerd was 3.27. I like the fact that I can drive around town in third or fourth and first gear is really useable and fifth is really smooth. The posi is like I remembe the old muscle cars where you punch it and it slides side ways and hit second and it will slide the other way not a lot its only a 3.9 180 hp rover.Now the questions. My speedo was reading 6 miles off now its 18 miles off how do I fix this. I guess if I ever want the edgeness back I could just ride on the highway in fourth and in fifth learn to catch Mustangs by downshifting to fourth going 60 mph. now its been three years with the old 3.9 rear so I know I will get use to it, the engine noise level is real nice going 70 and that is what I wanted. Thank you for letting me vent I know all I have to do is downshift or drive in a different gear. Saturday I am going to drive somewhere 100 miles or so to see what its all about. In the short run I am happy with the results.








dbw

You'll need a recalibrated speedo. Not sure what you have already, but if you've mated the LT77 to a standard 'B speedo, an MGC speedo (the car came with a 3.07 rear) might be an idea if you can find one.
Dave

What a great idea I placed threads on the MGC and MGBV8 sites. I drove the car 250 miles Saturday and I am really pleased with the 3.00 ratio, 70 mph at 2500 rpm nice an quiet. Saw a porshe and went to shift from fifth to fourth but hit second going 60 mph, pulled over to look at engine and nothing leaking and new rear is getting broken in quick. Do I need to change the gear oil after 500 miles, or not the gears are not new but the limted slip cluches are.I know in new cars I have owned I have never replace the rear end oil.
DBW

you can have your speedo recalibrated by Nisonger
email: info@nisonger.com
BOB FISHER

Various Rod shops can sell you a small box of gears that goes between your speedo cable and the box. They usually want you to drive 10 miles (or km) exactly and record what you odometer reads. They work ou the ratio from that and assemble acchordingly. My ratio with the supra box is 10kilometers=7'miles'on the speedo. ie when I'm going 100km/hr the speedo shows 70.

Local guys charge around $100 Australian, which would be about $50 US or less.
Peter

The speedo shop here is $100-150 for a recal if you need things adusted. That and the fact I wanted modern gauges, I went with a electronic speedo, this way I can recalibrate in seconds if I change tires, rear gears etc..

Larry

Congrats on the new rear end. Depending on the torque you have the 3.00's can be a good choice. Remember those stangs have usually 225hp, 250lb/ft of torque from the factory if they are a V8. No replacement for displacement. OH and they will have 2.73 or 3.08 gears and taller tires..
Larry Embrey

This thread was discussed between 11/08/2005 and 16/08/2005

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