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Overdrive relay

Discussion in '"Stock" Alpine' started by Van Bagley, Oct 6, 2020.

  1. Van Bagley

    Van Bagley Gold Level Sponsor

    Does any know where I can get a new relay? Sunbeam Specialities does not stock them.
  2. puff4

    puff4 Gold Level Sponsor

    I'm assuming you're talking about the one used on SVs. If so, they're NLA pretty much everywhere. If you do get lucky and find one on eBay or similar site you'll pay a lot - the only other application for them happens to be on Ferraris.

    Having said that, TomH has previously published a really nice solution to build your own, and I think Jerome at Alpine Innovations also has a product that will do the job.

  3. Gordon Holsinger

    Gordon Holsinger Diamond Level Sponsor

    Jerome at alpine innovations in the U.K. has reproductions for about $45 in either positive or negative ground.
  4. Tom H

    Tom H Platinum Level Sponsor

    I am 99% sure the Alpine Innovations solution is just about the same as my DIY solution, except they put the diode and resistor inside the relay case. Nice solution.
    puff4 likes this.
  5. sunalp

    sunalp Platinum Level Sponsor

    You can also contact Jeff Howarth in the UK. He sells rebuilt overdrives and their components.
    I just got one, and a bunch of other parts, this past Monday.
  6. Van Bagley

    Van Bagley Gold Level Sponsor

    Thanks all
    I bought the OD from Jeff about 10 years ago and I have his contact info
  7. Tom H

    Tom H Platinum Level Sponsor

    Just FYI, using any standard 4 pin or 5 pin relay either from a NAPA or similar store , or using a common Lucas 6RA relay (for a more Original look) and adding the parts as described in my write up, or using Alpine Innovations relay with the additional parts installed inside will provide a more trouble free operation. The original relay uses 2 contacts in parallel , one to "latch" the relay ON and the other contact to deliver power to the OD. The relay coil has just enough power to pull both contacts ON, and it is quite common that only one of the contacts closes, resulting in the solenoid and OD not engaging. In the 15 years I've been on this forum, I think that failure of the original special relay has been the most common cause of OD failure to engage, including my own.

    puff4 likes this.
  8. 737lindgren

    737lindgren Bronze Level Sponsor

    newbie here, my car doesnt have over drive, does it make sense to install an overdrive transmission
    sounds like a good investment . if I do do you buy the whole overdrive transmission then have it rebuilt or just the overdrive piece alone
  9. Tom H

    Tom H Platinum Level Sponsor

    An OD is quite nice if you plan to do much driving at freeway speeds. A stock SV, with original 13 inch wheels and no OD, has a 4.21:1 rear axle ratio, which yields about 4500 RPM at 70 MPH You might find a 3.89 axle from an earlier series (or just the pumpkin), which would reduce that to about 4100 RPM. But swapping in an OD gets you to a nice 3300 RPM with the 3.89 axle or about 3600 RPM with the stock 4.21 axle Adding just the OD to a stock tranny is problematic because it requires not just adding on the OD, but adding in a different mainshaft in the tranny. A guy in the UK, Jeff Howarth, often has a rebuilt complete OD tranny for sale. Last e-mail address I have for him is: jeff.v8tiger@gmail.com

  10. alpine_64

    alpine_64 Donation Time

    I have this combo with the added gearing of 195/65/14 rear tyres... Makes for a very comfortable freeway alpine.. Especially with hardtop on
  11. Gordon Holsinger

    Gordon Holsinger Diamond Level Sponsor

    Tom you are correct I am trying for an original look in the engine bay!
  12. 737lindgren

    737lindgren Bronze Level Sponsor

    thanks i will start the search
  13. hartmandm

    hartmandm Moderator Platinum Level Sponsor

  14. Tom H

    Tom H Platinum Level Sponsor

    Gordon, just FYI, my solution looks very much like original if you use a common Lucas 6RA relay, which looks identical. The added diode is just about invisible under the relay and the resistor is not obtrusive at all.

    See the photos in Mike's article above.

    Last edited: Oct 11, 2020
  15. 737lindgren

    737lindgren Bronze Level Sponsor

    thanks mike
    I had no idea this was so extensive
  16. Tom H

    Tom H Platinum Level Sponsor

    Chris, don't be discouraged by Mike's very instructive write up. He probably spent more time on the write up than he did doing the install! :
    It's one of the most straightforward improvements you can make. If you keep your original 4.21 axle you can probably find a speedo to match, but the factory never made an Alpine with OD and 3.89 so if you swap axles as well as OD, you'll need to do the speedo mod - or just use your GPS or tach to monitor speed. Mike's write up does a great job alerting you to all the details. Most of us figured them out on the fly - much nicer to know in advance. Unless it makes the task look to tough!,
  17. alpine_64

    alpine_64 Donation Time

    Tom, the factory did do 3.89 amd OD .. All the series 3 OD cars had the 3.89 standard trans or OD.

    Quite a rare speedo but they made them. Over the years ive tracked down 3
  18. Alpine 1789

    Alpine 1789 SAOCA President Platinum Level Sponsor

    My SV has an OD and 3.89 rear end. It also has 14" wheels and tires (185/65 SR14) and the combination ends up working well with a stock SV OD speedometer.
  19. Tim R

    Tim R Silver Level Sponsor

    This video from The Sunbeam Alpine Channel on YouTube shows real world driving with a non-overdrive rear axle (3.89) fitted to a car with an overdrive gearbox running on 165/80 R13 tyres.
    This gives very relaxed cruising with minimal loss of acceleration. The engine in this car is bored to +0.060, has the Vizzard Head modification but running with dish top pistons (Vizzard mod done to reduce over compression caused by repeated skimming of block and head over the years). It is a very smooth cruiser at motorway speeds.
    Coincidentally the speedo is amazingly accurate when measured against a sat nav speedo.


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