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Spitfire & GT6 Forum

Probably a weird gearbox question, but I gotta' ask

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JohnW63 John Williamson
Apple Valley, CA, USA   USA
Just how easy should it be to move the gearbox forks, with the top off the gearbox ?

All the gearboxes I have to play with were dried out and gummed up, when I took them apart. I had to put the tops in a vice and oil them down and spray in penetrating stuff to get them to move at all. Lots of soaking and moving got them feeling OK, to me. I didn't see any scoring of any sort. Now that the gearbox is on the chassis and attached to the engine, my Dad thinks it should be easier to move. ( Since the gearbox has no oil in it yet, and we don't have a pedal we can disengage the clutch with, I'm not sure how much motion and ease I should expect, to be honest ! ) It's an easy task to pop the top off, at this point and mess with it, so I thought I would find out what my goal should be for " easy to move off the gearbox ".



Home of the 1969 GT6+ MK II resurrection project
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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
It should lift off if it isnt stuck.

Why do you want it off?

trrdster Avatar
trrdster Wayne Tate
Spencer, NC, USA   USA
John, Did you flow some oil on the gears before closing it up?
If not, all parts are metal on metal and those top gears won't get any lub until you are going down the road. So a little stiff.
I spray some Slick 50 on the parts, but that's just me because I know it might be a while before things get oiled.



Wayne
1970 TR6
2000 Jaguar XK8
1949 Triumph Roadster 2000
1978 Spitfire (rust victim)
1971 GT6 (tarp covered for 12 years, rusted inside out)
1980 Spitfire (getting all the good GT6 parts, all poly suspension and Spax shocks)

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JohnW63 John Williamson
Apple Valley, CA, USA   USA
I was going to take off the top to fill it up and inspect how easily the three rails move by moving the gear shift lever. I doubt anyone has really thought about how easy those rails SHOULD move, when it's not attached to the gearbox, unless you're job is to rebuild the things. I just hoped someone would chime in that had rebuilt one, recently. I need to figure out HOW to hold it in a vice to work it around and see how easy it is. I know I can't move them WITHOUT it being firmly held in place. If it should move the forks around, with ease, maybe Dad is onto something.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

trrdster Avatar
trrdster Wayne Tate
Spencer, NC, USA   USA
John, if you just set it on there after doing the sideways dance to get the reverse gear to engage, just tighten down a couple of bolts and it should shift just fine, just a little notchie. If you turn the rear flange a bit you can feel how it's reacting. If it won't shift on the floor it's not going to in the car.



Wayne
1970 TR6
2000 Jaguar XK8
1949 Triumph Roadster 2000
1978 Spitfire (rust victim)
1971 GT6 (tarp covered for 12 years, rusted inside out)
1980 Spitfire (getting all the good GT6 parts, all poly suspension and Spax shocks)

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
In reply to # 1594333 by JohnW63 I was going to take off the top to fill it up and inspect how easily the three rails move by moving the gear shift lever. I doubt anyone has really thought about how easy those rails SHOULD move, when it's not attached to the gearbox, unless you're job is to rebuild the things. I just hoped someone would chime in that had rebuilt one, recently. I need to figure out HOW to hold it in a vice to work it around and see how easy it is. I know I can't move them WITHOUT it being firmly held in place. If it should move the forks around, with ease, maybe Dad is onto something.

With the top removed you should be able to move the lever and see the forks move to 1-2-3-4 positions quite easily (only ounces of pressure) if it is very stiff remove the top extension and see if the problem is there or in the rails.

Have you given consideration as to what oil you put in the box?

F1000RACER Avatar
F1000RACER Platinum Member Gary H
Alpine, CA, USA   USA
John
Are you saying it is difficult to shift with the gear lever installed? And you've tried rocking the output flange back and forth while trying to shift?

I'm also assuming you properly rebuilt your entire shift extension assembly and you've properly adjusted the reverse lockout bolt? If not do so. Just rebuilding the lever assembly isn't enough. The selector has a universal assembly just forward of the lever where it enters the housing. 99% of the time these are totally worn out. All of this adds up to a ton of lost motion.

After completing all of this about if it's still not shifting with ease there is likely something wrong. Bent shift forks can be a source, yes they can get bent very easily. Did you replace them or adjust them?

If its not smooth on the bench don't go forward. This is why I always bench test my gearboxes with oil in them.

GH

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Quote: I'm also assuming you properly rebuilt your entire shift extension assembly and you've properly adjusted the reverse lockout bolt? If not do so.

No, I did not. I didn't see any wear or sloppiness, and once we go it lubed and moving, I thought we were good. Sound like we are not.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Quote: Have you given consideration as to what oil you put in the box?

Redline MTL seems popular around this forum.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Quote: I'm also assuming you properly rebuilt your entire shift extension assembly and you've properly adjusted the reverse lockout bolt? If not do so.

Let me rephrase my response to the above. We did rebuild the gear shift extension at the "ball" end where the motion starts. That seems to move well. I did not take the other end apart, because it looked OK. It just had to rotate and move forward and back. So, no adjusting on the reverse lockout bolt. I figured that it was adjusted at the factory, and if it didn't need to be removed, I wouldn't need to adjust it. What was stuck and gummed up was the gearbox top, where the three rails live.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Quote: Bent shift forks can be a source, yes they can get bent very easily. Did you replace them or adjust them?

I did neither. They looked nice and straight. I chose the one of the two I had with the least amount of wear on the forks, as measured with a caliper.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
In reply to # 1594363 by JohnW63
Quote: Have you given consideration as to what oil you put in the box?

Redline MTL seems popular around this forum.

thumbs up

Good! Just thinking you might accidently use something totally unsuitable.

Also (if I might say so) your actions so far seem perfectly reasonable. I am sure the transmission will work out for you, and applaud your precautions.

JohnW63 John Williamson
Apple Valley, CA, USA   USA
Got it figured out . I took the top and shift extension off and we found the main shaft was locked. It would not spin freely even in neutral. If I backed off the nut on the flange things got better. Some head scratching and staring at the exploded parts diagram followed. The diagram showed a thrust washer ( part 44 ), that was supposed to be between the gearbox extension bearing ( ball race ) and the the speed-o gear somewhere. My Dad figured something had to keep the pressure from the flange from trying to be transferred to the main shaft and then the gears in the box. So, off came the extension. ( I'm going to post a quick FYI thread about how we got it off really easily. ) There was no washer. I got so happy about getting the gears and shafts IN the gearbox, after lots of hassle, I had not put one on. Turns out , I couldn't put one on because the washer from a Mark II gearbox is too small for my new Mark III main shaft. I had to go buy a washer of the right size for the shaft and then carefully grind the outer edge down enough to let the extension slide over it. Once that was in, I tightened the nut as far as I could and the gearbox still spun just fine ! We also added more lube to the rails and made sure that was all slippery. I put a good dollop of RedLine MT-90 all over the gears before we closed it up. It moves much nicer now. I'll top it off with the RedLine MTL, when it shows up.



Home of the 1969 GT6+ MK II resurrection project
and a sorry looking 1968 GT6+ parts car trying to stay whole.

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