Drive In, Drive Out Diff Exchange

[Forrest Gump]

You could use a GPS unit that also shows speed and at certain speeds like 40 MPH compare what the speedo on dash shows and what GPS says and see what the percentage difference is
Then do the math to see which inner or outer gears are needed to correct or try this :

Speedometer Gear Calculation
Speedo Revs/mile = (20168 x DiffGear x DriveGearTeeth) divided by (Tire-diameter x Driven-GearTeeth)

Or here is another speedo gear calibration calculator

Calculate Speedo Gears

Thanks for your help. I’ll see if I can get a 17 tooth driven gear, that should get me nearer correct.

 

[Adtheman]

I had my diff. sorted a few months ago. Got all the parts from Scott, but a local garage did the work.
Out of interest Adtheman what did it all cost doing it your way? If you dare tell us

Mine was a bit more involved as i changed the half shafts and some other bits too. Labour was 7.5 hrs and his rates are very reasonable. i daresay my cost will have been similar to yours as i'm guessing your local garage would be a similar labour rate or less but maybe took a little longer. I know i wouldn't have been able to do it laying on my garage floor.

 

[teamzr1]

Look closely as the white and gray are close in color

 

[Forrest Gump]

I can't imagine doing it without a ramp and all the gear thats quite an achievement.

It’s not too bad. Popping the cross member out of its sockets can be stubborn if not been off before.
Then trolley jack under the diff to raise / lower that bloody heavy lump of cast iron. No way could you lift it.
The Corvette racers might have a couple of diffs with ratios to suit different tracks and think nothing of a diff change.

 

[Forrest Gump]

Look closely as the white and gray are close in color

View attachment 13743

Don’t think they’re for a C3 ’box are they?
I‘m looking for one like this in fetching purple..

 

[Chuffer]

Don’t think they’re for a C3 ’box are they?
I‘m looking for one like this in fetching purple..

View attachment 13745

Oooh ! I `ll have to get one of them too , it will match the bodywork ! Seriously though , I need to get mine up in the air and check the speedo drive as the needle bounces about all over the place at times . Might be the speedometer damper knackered though . Its on the winter tinkering list !

 

[teamzr1]

Looks like this then

 

[kentvette]

I can't imagine doing it without a ramp and all the gear thats quite an achievement. 800 miles is a long way but i guarantee you won't regret it.

What's more, we did it twice in about three years - the first time to change yokes, which probably exacerbated the later more catastrophic episode!

Scott's been a great help, and I'm sure he's the man to have a look at some things I'd like to get sorted. Just need to work on the logistics of foreign travel etc!