Speedo calibration with Getrag 5 speed - instrument refurbishing

[Scottcorvette]

I would like to send my instruments away to be restored. I would prefer to get this done ahead of the game as I was planning on using Speedy Cables for this and they always have a backlog so there is usually a bit of a wait. it would make sense to get the speedo recalibrated to suit the Getrag 5 speed that I am going to fit. Does anybody know what the discrepancy is, does it read too high or too low and by how much?

Car is a 1964 230SL with the stock rear end, I had it in mind it was a 3.75 but reading the tech manual it should be a 4.08 on a USA car so I'll need to double check it today. When I buy an aftremarket transmission for a Corvette they can calculate what speedo gear I need for a specific rear end and tyre size but I guess we don't have that luxury here, I wonder if they can calculate it from that info plus the number of teeth on the drive gear and driven gear.

Any other recommendations for the instrument overhaul in the UK, I would like the speedo and tach going over, the tach used to stick unless you gave it a couple of taps, I would like to get the centre cluster refinished and the clock done. they all need needles refinishing and bezels rechroming etc

I think my clock will probably need a new bezel and lens.

[stickandrudderman]

Chrome bezels are available from SLS, as are dial faces.
I fit custom electronic speedo drives which can be calibrated according to your diff ratio and tyre size.

[Scottcorvette]

Th gauge faces are nice, the needles are a little faded so could do with being redone. I am assuming they would be able to get the bezels off and rechrome, or are they goosed when they come off? The clock bezel has a dent so that will need replacing. the lens is plastic so I guess a new one could be cut. are the later ones glass?

So your speedo drive, does that use a pulse generator in the transmission to then convert to mechanical? I did look at one of those on an american website but read reports of the needle being a little jumpy. I saw that right after I had gone to great lengths and expense to get the elusive mechanical speedo drive.......

[stickandrudderman]

I tried the American one and didn't like it so, in conjunction with an electronics designer friend who's also a petrol head, we have developed our own product that is pre-calibrated according to your tyre size and diff ratio. We made three prototypes which are all now fitted to cars and working. The MK2 model is going to be a much smaller version that will connect directly to the back of the speedo in place of the cable.
We may or may not decide to allow user calibration but at this stage it's not an option.

All central instruments should have glass not plastic but I'm not sure of the clock.

Chrome bezels are easier to change than you think.

[gordon]

Hi, Do i have to wreck the chrome bezel on my rev counter to remove it because the silver disc on the needle has dropped off and i need to fix it back on. Gordon

[Jonny B]

There are several posts on the removal of the chrome bezels on the instruments. The key words are patience and slow. My friend and I took the one of the center instrument, and just carefully bent the the trim from the back where it crimps on to the instrument case. It is amazing how much difference just cleaning the glass can make.