The 'E' Type Forum

Hello, can anyone recommend who I should talk to about parts availability for LdM OD's? I was assuming O/D Spares in Rugby (odspares@aol.com) but have had no response to date. At the same time I note an old PeterCrespin post that includes "...the Laycock engineers who run the repair place in Sheffield..."
Might these be the same or different?
Thx

I got my spares from odspares. Very nice and helpful contact. Just wait, maybe nag them.

If someone here lives nearby, it may be an idea to go and have a look ?

Carsten (Klick!)

Overdrive Repair Services is definitely in the Sheffield area and I can recommend them. Their address is

1, 50 Rother Valley Way, Holbrook, Sheffield S20 3RW

Phone: 0114 248 2632

I have not come across OD spares in Rugby

I used the Sheffield guys to have my O/D rebuilt and can recommend them for their work and customer focused attitude.
Cheers .......... Ole

Hi,

Another positive vote for O/D Spares in Rugby, this is where I got all the parts for my uprated rebuild.

Dave definitely prefers to discuss by phone & he's picked up both times I have called him in the last week.

If time zones allow give him another call on Monday?

Good luck,

Dave.

Thx peoples, I will persist. Maybe write them a letter ...

I have most parts to service a compact OD please feel free to drop me a line with what you need

Thx Tony I certainly will, od (Compact type A) needs a lot. But not if I cannot first buy or swap a mainshaft, to convert my gearbox from a KF to a KFN type. So currently I have "all points bulletin" out for a kfn gearbox from xj6 s1 or s2 ...
How come u have OD parts?

I repair Overdrives quite often and mainly compacts. Good luck finding a mainshaft thin on the ground
these days...... I also have a few complete MOD gearboxes to suit. Any all synchro Jaguar OD box mainshaft
will suit part number C21939

Woo hoo, check this out, OD and mainshaft ready to be fitted…



Big thx to TonyA, also Dave of OD Spares in Rugby, Oz/UK tag team that made this happen for me. Highly recommended. TonyA has a collection of Copact Type A OD box’s to go if anyone local is interested.



Now to figure out the wiring. Seems Lucas and Laycock don’t agree on the polarity …




Something to check when I choose me a relay …

Moving forward. Good luck ..... Ole

My solution for O/D control is a bit more involved, but gives me the knowledge that I don't forget the switch is in "O/D mode" when leaving 4th gear and the O/D button is integrated into the gear knob.

Hmm someone knows their electrics. I prefer the KISS philosophy, maybe why I'm leaning towards lucas relay, 4 terminals instead of 5 ... ;D
Knob is neat. I'm going "traditional", stick is jag from oz, knob is triumph from us, switch is MG from uk ...

The black block in my control box is the modern $3.00 version of the Lucas relay.

I reckon the white thing is the relay. KAE brand, used by Volvo. I’m guessing that the black block is a transistor that, together with the rest of the electrics, automatically disengages yr overdrive when you change out of 4th gear, as well as enabling that 1-position switch on yr knob, press it once to engage or disengage OD?
Mine will be more basic, with 2 position IN/OUT switch. My understanding: when I change out of 4th OD will automatically disengage BUT, when I change back to 4th, OD will automatically reengage, if I haven’t manually switched to the OUT position.

The early MGBs were fitted with an over drive and incorporates a vacuum operated switch so if you switch the over drive out while your throttle is closed it keeps it engaged until you press the accelerator. As soon as you press the accelerator the overdrive will disengage . It means you do not get the disengagement jolt which happens if you disengage the overdrive with the car slowing and the vacuum switch not working or not fitted. Works brilliantly on my MGB. Sadly the later cars did not include the vacuum swiitch. Slightly more complex wiring....
and in case you are unaware NEVER put the car in reverse if you think the overdrive is engaged or severe damage will result.

lowact wrote: ↑

Sun Jul 22, 2018 12:58 am

I reckon the white thing is the relay. KAE brand, used by Volvo. I’m guessing that the black block is a transistor that, together with the rest of the electrics, automatically disengages yr overdrive when you change out of 4th gear, as well as enabling that 1-position switch on yr knob, press it once to engage or disengage OD?
Mine will be more basic, with 2 position IN/OUT switch. My understanding: when I change out of 4th OD will automatically disengage BUT, when I change back to 4th, OD will automatically reengage, if I haven’t manually switched to the OUT position.

You're right about the Volvo relay. That's the one in conjunction with the oblong board with electronic bits that gives me the push button operation as well as ensures that the O/D remains disengaged when I leave 4th gear and re-engage 4th without touching the push button.
The black box is the relay that handles the 20A peak current drawn by the O/D solenoid as well as changes the negative polarity supplied by the Volvo relay to a switched +12V.

Hi Colin,
You really dont need a relay for the OD but some prefer it. Most of the time a relay was fitted later due
to a problem with wiring or a switch issue. Jaguar never used a relay on OD cars as the holding current of the
solenoid is usually just above or below 1 amp the initial current draw is around 15amps. but I suppose its what you prefer really.... All the best

You really DO need a relay and you also need to have a separate fuse for the overdrive solenoid additional circuit. Simply fitting a larger value fuse and incorporating that into your car's loom will provide the upstream part of the loom with little or no protection from your modifications, much like fitting a 50amp fuse for an "upgraded" fan on your radiator - the wiring will melt long before the fuse ever blows. Check my previous posts on electrical topics for details.

In the case of the overdrive solenoid, it does indeed add about 16amps to the current draw to fire up the overdrive. Once engaged a small armature is supposed to disconnect and leave it running with a current draw of about 2/3amp. Sadly, if there is corrosion on the contacts of that armature, it may not disconnect and will permanently pull a high current. This is a realistic possibility for these cars these days, as they are not used on a daily basis and the default position is a "closed contact" that may well never disengage.

Most relays are not polarity sensitive with regard to which coil winding is connected to positive or negative supply. Only those with a fitted diode across the coil windings are and the diode "points" to the more positive contact, regardless of whether you have a positive or negative earth car. (Relay boxes containing electronic circuits may be different, but they are generally not marketed with the basic W1,C2 etc or 87, 86 etc terminal designations.)

kind regards
Marek

I note XJ6 S1 & S2 didn’t have an O/D relay, power was from the reverse light circuit, upstream of the gearbox switch, directly to the solenoid via the two switches. Etype S3, reversing lights are via dedicated wire from fuse #7, 35A. Fuse #7 also protects windscreen washer, heater fan, instruments, horn relay winding. If I don't change the fuse, leave it at 35A, no wiring could be overloaded? If this fuse doesn't blow, no relay required?

I only responded to this thread because Tony gave contradicting advice. With the first sentence he said a relay wasn't needed and in the second sentence he said they were retrofitted when there had already been a problem. That means there obviously are problems which are not properly understood or addressed first time around.

The "problem" is that the wiring going into and back out of the gear lever knob where the overdrive switch sits is a thin spindly gauge of wire and cannot withstand 15amps persistently, which is the error condition I suggest you plan for. The thin wire wi'll melt long before the fuse blows and it'll take other bits of the harness with it when it does. Fuses don't prevent equipment or harness from malfunction - they react to the malfunction. I can think of no other circuit in your car which runs 15amps with such a thin gauge wire. All of the big currents are handled by thicker gauge wire for a reason. With the circuit as proposed by yourself, there is no guarantee that the 35amp fuse will blow before the wiring has already melted.

When doing modifications, you have to plan not only for the "it works" scenario, but also the failure mode when it doesn't work, to give yourself a safe fall-back position.

kind regards
Marek