Fitting a new Speedo Head

[Cornish Rattler]

Hi guys

I want to fit a S3 speedo head ( gauge / clock ) to my late 2a due to me fitting the 200tdi, I've looked on ebay for a speedo head that has similar mileage to mine but to no avail and as the rebuild is nearing completion I've been thinking about fitting a new speedo head rather than a used one, but want to know is it just a matter of fitting a new speedo head and off you go or do I need to tell DVLA that I've fitted a new speedo head 

[lo-fi]

They're easy enough to take apart and roll the numbers around to match your existing one. I've literally just done that this eve with a Smiths unit I've been given to match my Smiths rev counter. 

I had to change a broken speedo on my old RX7 and ended up with one that had far fewer miles on it. Went through MOT which records the mileage and nobody batted an eyelid that it had gone down since the last. But who knows what goes on at the DVLA... I'd keep a clear record either way. 

[steve b]

If you change to a series 3 speedo you will need to change the cable too . Why does the 200Tdi necessitate a change ?

As I understand it you don't need to inform DVSA , but it could be noted at your next MOT if you ask the tester log it as an advisory

cheers

Steve b

[Snagger]

I don’t see the need for a change either, unless you change the final bearing ratio (diffs or tyre size).  The Tdi won’t make you go faster at the top end - it’ll just get to the speed sooner and hold it on steeper inclines or into stronger headwinds.  In fact, you’ll probably be a bit slower due to the cacophony the Tdi produces at 3000rpm+ compared to the earlier engines, including NADs.

If it is because of recalibration for a diff or tyre size change, than I can recommend JDO-1.com.  He services and recalibrated Speedo’s, which is cheaper than buying new and safer than second hand.

[Cornish Rattler]

9 hours ago, steve b said:

If you change to a series 3 speedo you will need to change the cable too . Why does the 200Tdi necessitate a change ?

As I understand it you don't need to inform DVSA , but it could be noted at your next MOT if you ask the tester log it as an advisory

cheers

Steve b

Yeah i have the S3 cable as well, yeah i've added an ashcroft transfer box and Def diffs to match the engine 

[Snagger]

Use HRTC or  3.54 diffs, but not both!  It’ll be a terrible drive with both, with sluggish acceleration and poorly geared for town and narrow lane driving, and you will shear the teeth off third gear sooner or later (as I did using overdrive and 3.54s and Ed Parrot did a little while later in his 88, doing just the same with Tdis).  I’d recommend just the HRTC so as to leave the speedo and low range unaffected.

[Cornish Rattler]

52 minutes ago, Snagger said:

Use HRTC or  3.54 diffs, but not both!  It’ll be a terrible drive with both, with sluggish acceleration and poorly geared for town and narrow lane driving, and you will shear the teeth off third gear sooner or later (as I did using overdrive and 3.54s and Ed Parrot did a little while later in his 88, doing just the same with Tdis).  I’d recommend just the HRTC so as to leave the speedo and low range unaffected.

Well its all in now will have to see 

[lo-fi]

Not meaning to sound negative... I'd have a pair of 4.7 diffs and gaskets on-hand, painted up and ready to go. 

[Snagger]

3 hours ago, Cornish Rattler said:

Well its all in now will have to see 

Don’t, or you’ll be replacing more than just the diffs; you’ll be rebuilding the gear box.  Fuel consumption will be worse than with just the one gearing increase, too, as the engine will be working too hard and you’ll spend more time in the lower gears.  Just use the HRTC, and you won’t have to worry about the speedo.

[Cornish Rattler]

10 hours ago, lo-fi said:

Not meaning to sound negative... I'd have a pair of 4.7 diffs and gaskets on-hand, painted up and ready to go. 

Yeah i still have the the old 4.7's just incase 👍

[steve b]

Swapping the back out to test on the road is a quick  job , why not do that to start with ? As snagger said it then negates messing around with the speedo too.

Just a thought

 

Steve b

[Snagger]

Just for a bit of psychological comfort, HRTC bumps the high range by about 32%.  3.54s are about35% taller than 4.71s (but messes up low range and the speedo).  Overdrive can be used for both high and low at will and doesn’t screw up the speedo, but only raises the gearing 28%.  So your HRTC is going to do a pretty good job by itself.

Driving in 1-3 with two of those options will break the gear box sooner or later.  Yes, the Tdi can pull more than just one of them, but it can’t pull two.  I will eventually be fitting 4.1 diffs, low enough to give decent acceleration and low speed manners with the overdrive disengaged and for the engine to manage to pull them with overdrive engaged on the motorway, but the key point is that I will only ever be using overdrive as a fifth gear, not in 1-3.  Unfortunately, you can’t protect the gear box from the torque in the same way with HRTC being permanently “engaged”.  If you really want more than just one of those increases, then you either need to go down the Defender transmission route, fit 9.00s or similar, or do what I’m doing, but even the 9.00s with HRTC is a risk on the box in my view.