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Over Drive Transmission Interchangeability

Discussion in 'Modified Alpine' started by DanR, Feb 7, 2018.

  1. DanR

    DanR Diamond Level Sponsor

    Wondering if anyone has looked at the OD from the early Volvo '63-'65 P1800 being utilized in the Alpine?

    Both my '63 Volvo P1800 Coupe and my '65 SIV Alpine have Over Drive tranny's. They (the OD) units sure look alike!

    Might explore farther!

    Also have a later '79 model Volvo OD Unit 28K miles that is much heavier looking! Any ideas out there as to whether it could also be a good substitute?
  2. Bill Blue

    Bill Blue Diamond Level Sponsor

    Dan, there is some sort of interchangeability among the different overdrive units. That was a pretty hot topic 10-15 years ago, but I had already decided to go the re-engine route, so I paid no real attention. Besides, I am convinced the problem with the Alpine overdrive is not the overdrive unit, but the transmission output shaft. It likes to take on a permanent twist and the OD unit will not shift. Common wisdom is the twist is from power shifting. I think it is from down shifting the OD with a closed throttle. Especially when in 3rd gear. If you could use an OD with the non OD output shift you'd have a winner. I think. But I don't know, mostly BS-ing with a friend.

    Back in the day, when I bought my Series II, the salesman told me I could not hurt the OD. Shift any way, anytime I wanted. It lasted about 25,000 miles. The lurch from closed throttle closed throttle downshifting third was much greater than any power surge I could muster with the 1600.

  3. DanR

    DanR Diamond Level Sponsor

    I tried to do a search of the Forum for the OD with no results. I'm not good at doing some searches.

    I main concern is the "65 SIV Alpine I've had for years that came fitted with the OD. Even though I was not much into power shifting up or down, It functioned well for me then.

    It has sat in storage for a good many years and will need some attention.

    Everytime I open one of my sheds and see the two "other" OD's I can't help but wonder if there is some interchange? I especially like the '79 Volvo OD... much stronger too! O'well, my plates full of other projects at the moment, so I'll put that back on the shelf:)
  4. Ken Ellis

    Ken Ellis Donation Time

    I'll bet Volvoguys will know. I was steered to a Volvo OD repair resource locally many years ago for help with my Alpine OD, but didn't have a current need. Now that I do, they're gone or out of the business.

    Regarding your searches, when I try a Google site search it returns what must be links to the old forum postings, which don't seem to reflect the new ones. Perhaps Google is (or should be) re-indexing our site?
  5. Barry

    Barry Platinum Level Sponsor

    Borrowed from Wikipedia:

    The vast majority of overdrives in European cars were invented and developed by a man called de Normanville and manufactured by an English company called Laycock Engineering (later GKN Laycock), at its Little London Road site in Sheffield. The system was devised by Captain Edgar J de Normanville (1882–1968),[2] and made by Laycock through a chance meeting with a Laycock Products Engineer. De Normanville overdrives were found in vehicles manufactured by Standard-Triumph, who were first, followed by Ford, BMC and British Leyland, Jaguar, Rootes Group and Volvo to name only a few. Another British company, the former aircraft builder Fairey, built a successful all-mechanical unit for the Land Rover, which is still in production in America today.

    The first production vehicle to feature the Laycock system was the 1948 Standard Vanguard Saloon. The first unit to be created was the A-type overdrive, which was fitted to many sports cars during the 1950s, and into the late 1960s. Several famous marques used A-type overdrives, including Jaguar, Aston Martin, Ferrari, Austin-Healey, Jensen, Bristol, AC, Armstrong Siddeley and Triumph's TR sports car range, from the TR2 through to the end of the 1972 model year of the TR6.

    In 1959, the Laycock Engineering Company introduced the D-type overdrive, which was fitted to a variety of motor cars including Volvo 120 and 1800s, Sunbeam Alpines and Rapiers, Triumph Spitfires, and also 1962-1967 MGBs (those with 3-synchro transmissions).

    From 1967 the LH-type overdrive was introduced, and this featured in a variety of models, including 1968–1980 MGBs, the MGC, the Ford Zephyr, early Reliant Scimitars, TVRs, and Gilberns.

    The J-type overdrive was introduced in the late 1960s, and was adapted to fit Volvo, Triumph, Vauxhall/Opel, American Motors and Chrysler motorcars, and Ford Transit vans.

    The P-type overdrive marked the last updates and included both a Gear Vendors U.S. version and a Volvo version. The Volvo version kept the same package size as the J-type but with the updated 18 element freewheel and stronger splines through the planet carrier. The Gear Vendors U.S. version uses a larger 1.375 outer diameter output shaft for higher capacity and a longer rear case.

    Over a period of 40 years, Laycock Engineering manufactured over three and a half million overdrive Units, and over one million of these were fitted to Volvo motorcars.

    In 2008 the U.S. company Gear Vendors, Inc.[3] of El Cajon, California purchased all the overdrive assets of GKN to continue production of the U.S. version and all spares for J and P types worldwide.

    The system features an oil pressure operated device attached to the back of the standard gearbox operating on the gearbox output shaft. Through a system of oil pressure, solenoids and pistons, the overdrive would drop the revs on whatever gears it was used on by 22% (.778). For instance, the overdrive system applied to a Triumph TR5 operates on 2nd, 3rd and top gear. When engaged, the overdrive would drop the revs from 3000 by 666 RPM, or from 3500 the drop would be 777 RPM to 2723 net. The advantages this reduced rpm had on fuel consumption was most often quite near 22% decrease during highway driving.

    I don't have any idea whether or not Gear Vendors has anything for the type D / Alpine overdrive unit, but they are the successor to Laycock and GKN. I do know that Gear Vendors overdrive units are used in some enormously powerful rear drive cars.

    Last edited: Feb 7, 2018
  6. alpine_64

    alpine_64 Donation Time

    To my understanding the " overdrive" units are universal, hence their ability to be used on many cars. There are different final drive ratios.

    The unit is universal but each car has a different adaptor ( od unit to back of gearbox) and a mainshaft that goes from od unit to the gearbox.

    If you have a sunbeam adaptor and mainshaft you could use any other d type od unit.

    The end of the shaft into the od unit is also universal. So if you got a volvo d type od shaft and cut and spliced the od end onto a rootes mainshaft you could make a rootes od mainshaft
  7. Mike Broome

    Mike Broome Silver Level Sponsor

    I have fitted the stronger J type to my series 5. This was suggested due to my 140 bhp at the f!ywheel. It required the gearbox output shaft to be changed for the later fine splined as fitted to the later Hunter range. It also required a simple modification to the mounting. I have also modified the top gear lever housing to give overdrive on all forward gears. To protect the unit I always dip the clutch on upward changes and flip out the unit on downward changes. I also think it gives quicker changes.
  8. William Lewis

    William Lewis Silver Level Sponsor

    I have a series II OD gearbox to which I had mated a Volvo P1800 overdrive. I had to change the prop shaft to an MBG unit and shorten the prop shaft a little. That worked OK for 20 years, but the transmission output shaft had a slight twist to it when I installed it and about 2 months ago it finally twisted apart. I have obtained a series V OD transmission, but my Volvo OD unit will not fit onto the transmission. The Series 2 output shaft was uniform diameter from the pump lobe all the way back to the splined end. The Series V gearbox is 0.050" thicker from the pump lobe to about an inch back and then drops down to the same diameter as my older gearbox. To get my old Volvo unit to work, I will need to replace or drill out the center top hat bushing. Overdrive Spares tells me that the early 32% reduction ODs had a different top hat bushing from the later 25% reduction units. Has anyone else run into this problem?
    Last edited: Oct 14, 2019

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