-
Hey Guest!
British Car Forum has been supporting enthusiasts for over 25 years by providing a great place to share our love for British cars. You can support our efforts by upgrading your membership for less than the dues of most car clubs. There are some perks with a member upgrade!**Upgrade Now**
(PS: Upgraded members don't see this banner, nor will you see the Google ads that appear on the site.)
-
When posting a classified ad, you MUST select a prefix from the drop-down next to the subject line. If you don't you will get an error and your ad will not be posted!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
overdrive applications
- Thread starter hymodyne
- Start date
Share this page
Hi there. An overdrive unit will not bolt on to an existing non-OD transmission, you need to modify the existing gearbox with a different main-shaft. The OD units themselves also varied a bit is size and may not just drop right into place.
Didn't GT6+ come with D-type OD originally guys?
Didn't GT6+ come with D-type OD originally guys?
TR3driver
Great Pumpkin - R.I.P
Offline
In addition to the right mainshaft (which has to match the transmission gear set as well as the OD model), you also need the right adapter housing.
But later Spitfires used a J-type, so you might be able to retrofit the combination into your GT6. I see John Esposito has the Spit 1500 gearbox listed as "Spitfire/GT6":
https://www.quantumechanics.com/categories.php?op=newindex&catid=5
Many of the J-types listed on eBay "for TR6" are actually Volvo units. The sellers have learned that they get more money when they advertise them for TR6, and generally don't bother to mention that they have the wrong (or no) driveshaft flange, speedometer drive, hydraulic pressure, etc. and of course lack the mainshaft & adapter to install them to a non-OD gearbox.
But later Spitfires used a J-type, so you might be able to retrofit the combination into your GT6. I see John Esposito has the Spit 1500 gearbox listed as "Spitfire/GT6":
https://www.quantumechanics.com/categories.php?op=newindex&catid=5
Many of the J-types listed on eBay "for TR6" are actually Volvo units. The sellers have learned that they get more money when they advertise them for TR6, and generally don't bother to mention that they have the wrong (or no) driveshaft flange, speedometer drive, hydraulic pressure, etc. and of course lack the mainshaft & adapter to install them to a non-OD gearbox.
V
vagt6
Guest
Guest
Offline
I installed a Volvo J-type in my MKII GT6, quite a fabrication project but it worked great. No GT6 was delivered with a J-type, only D-types (Andrew, that's right, isn't it?).
J-type gearbox is longer than the D-type so new gearbox mounts must be fabricated. Made mine out of angle iron, drilled new holes a few inches aft of the stock mounting holes. Wiring harness for the J-type is easily fabricated and you'll need a different angle drive for the speedo. Quantum has them, as do other vendors. Also, the propshaft is shorter, obviously, but the stock one can be cut to fit.
Nothing at all wrong the a D-type, they're easier to install, significantly less expensive, and correct for the car (GT6). Unless you drive the car very hard or thrash it on a regular basis, I'd go with the D-type for all the above reasons.
J-type gearbox is longer than the D-type so new gearbox mounts must be fabricated. Made mine out of angle iron, drilled new holes a few inches aft of the stock mounting holes. Wiring harness for the J-type is easily fabricated and you'll need a different angle drive for the speedo. Quantum has them, as do other vendors. Also, the propshaft is shorter, obviously, but the stock one can be cut to fit.
Nothing at all wrong the a D-type, they're easier to install, significantly less expensive, and correct for the car (GT6). Unless you drive the car very hard or thrash it on a regular basis, I'd go with the D-type for all the above reasons.