Spitfire Spitfire Driveshaft - Which End Where?

[dklawson]

Some of you may remember that I am fitting a single rail gearbox to our '72 Spitfire project to replace its worn 3-rail box. I'm doing this with the help of my son so it's going to be a slow process.

I have ordered the new friction disk. I've also purchased the late model speedo cable and the shorter (38") driveshaft from a late model Spit to complete the transplant.

My son and I are ready to pull the gearbox and we (I) have a few questions before we proceed. It's been years since I did this with the GT6 so humor my probably obvious questions.

First, the gearbox is now only held on by a couple of bolts on the bellhousing and the rear transmission mounts. From memory... I believe I supported the back of the GT6 block with a floor jack so I could pull the gearbox up and back out into the passenger compartment. Is that whats' normally done with the Spit?

Second, the 41" driveshaft that came out of our '72 was the "strap-type". Each end had a round flange. The 38" driveshaft is the later type with a CV joint on one end. I've never seen these installed. One flange is rectangular, the other round. The bolt pattern on each flange is identical. So... which end of the CV joint type driveshaft goes where? Does the CV go towards the gearbox or the differential?

Third, there were two (reverse?) switches on the gearbox, both on the top cover... one in the back tucked under the shift extension, one on the front towards the bellhousing. Why are there two switches on the 3-rail gearbox when the single-rail box only has one?

Lastly, I was told I need to cut away a bit of the transmission tunnel in the tub to fit the single rail box. I know the single rail is roughly 3" longer and that I'll therefore need to cut out about 3" from the tunnel. Can anyone shed some light on this? Pictures or web links would be a great help.

Thanks.

 

[Norton47]

Hi
I pulled the engine and trans together on my Spit but once pulled the TR6 trans out the way you describe. Looking over the Spit I can see no reason it work work the same way. My is all apart right now. It's a 1975 1500 with O/D.
I measure a 27" cutout from the firewall to the propshaft tunnel. I measure 7.5" from the trans rear mount plate to the propshaft tunnel.
My O/D has 3 switches total. On on the single rail, one on the gearbox lid and one very small one on the shifter lever housing. So not sure if that is much help.
I would think the c/v goes to the differential. I have the strap type. But when thinking about changing propshafts that was what I was told.
I will try and get some photo's later.

 

[71MKIV]

I've always seen them with the cv joint front.

I am pretty interested in the body changes. As I am putting a single rail o/d in my 71. I am hoping that I don't have to get a new tunnel to do this.

hmmm, gonna go check the parts catalog at Spitbits, are the early and later tunnels different?

Steve Spangler
71 MKIV "Jehu"

Where are all those flashbacks they promised me.

 

[dklawson]

Again, my comments are hearsay since I haven't done the swap yet. However, I was led to believe the change is not to the plastic/paper tunnel cover. It's my understanding that the part of the tunnel that's on the tub itself has to be cut back because the single-rail gearbox is longer.

Thanks for the info on the driveshaft. That makes sense to me. The CV would probably collect road dirt and debris if it were mounted in the rear.

 

[Andrew Mace]

First, the gearbox is now only held on by a couple of bolts on the bellhousing and the rear transmission mounts. From memory... I believe I supported the back of the GT6 block with a floor jack so I could pull the gearbox up and back out into the passenger compartment. Is that whats' normally done with the Spit?

Yes. A good block of wood between jack and oil pan will suffice, and you only need to raise the engine a bit to pull the gearbox out.

Third, there were two (reverse?) switches on the gearbox, both on the top cover... one in the back tucked under the shift extension, one on the front towards the bellhousing. Why are there two switches on the 3-rail gearbox when the single-rail box only has one?

I'm not as familiar with the single-rail boxes, but one of the two switches on your three-rail (I think it's the one under the extension) is the backup light switch and the other is for the seat belt warning light. The latter actuates the warning light in any forward gear unless the seat belt is buckled (IIRC).

Lastly, I was told I need to cut away a bit of the transmission tunnel in the tub to fit the single rail box. I know the single rail is roughly 3" longer and that I'll therefore need to cut out about 3" from the tunnel. Can anyone shed some light on this?

I'm pretty sure it's the propeller shaft (driveshaft) tunnel that needs cutting, mostly so you can access the nuts and bolts to fasten the flanges together. But hopefully someone will have pictures for you!

 

[Trevor Triumph]

I have the CV joint at the front- at the transmission end. The CV drive shaft mated to my single rail transmission and OD unit. The other end had the small yoke that matched my MKI, 4.11 differential. I had a strap drive shaft and mounted it starps in front because it was that way when I bought the car. The person I bought the car from semed to have a lot of experience rebuilding British cars. I have seen pictures with the joint and strap at the differential end. One of the Spitfie books show the sliding spine shaft mounted to the diff also. The John Thomison book shows the sliding spline, stap and CV joint at the diff.
I had to cut away some of the tunnel- maybe two inches- on the MKI Spit, but not the MKII.
There may be two switches on the top of the single rail transmission to enable or inhibit overdrive, another may be for the back-up lights. T.T.

 

[Dennis]

Hi,
Well, when I changed the trany in my 74 1500 ( back in the 87 time frame ). I swapped it with a trany that had a J-type od that was in a 75. I didn't have to modify any sheetmetal for it. Just changed the rear transmission mount over along with the shorter drive shaft and of course the clutch due to the difference in splines. But it was pretty straight forward if my memory serves me right...
Dennis

 

[dklawson]

So I'm not surprised when we try to fit the single-rail box... what changes with the rear mount? That's one component that was not mentioned to me previously. Do I need a mount from a later car... or do I reposition the mount from the 3-rail box? Or... am I reading Dennis' comments incorrectly... does the rear mount only change when fitting the OD tranny?

 

[Dennis]

Hi Doug,
Yes, the rear mount had to change in my situation because I was putting in the overdrive. Otherwise I could have used the same rear mount.
Dennis