Heavy shifting > RBT with cable shift and Olthoff shifter upgrade

Markus

SPRF40
Lifetime Supporter
Hello all,

Shifting was always on the heavier side – so far so good.
But recently I made day trip and in the following week I had some shoulder issues…. maybe I’m getting old or that was a coincidence but now I want to change this.

Shifting forward and backward is OK but shifting to the side is very heavy.

Setup:
  • RBT
  • cable shift
  • Olthoff shifter upgrade
Does anybody have some suggestions how to approach this issue?

Plan would be to:
  1. Disconnect the cables and try to isolate where the highest resistance is coming from
  2. Then, depending on 1., greasing the various linkages and joints
  3. Potentially lubricate the shifter cables (is there good way to do with the cables still in the car??
What are your thoughts on this – any ideas or experience on this? The search did not bring desired posts....

Thanks in advance.

Markus
 

Neil

Supporter
Markus;

Look for tight radius bends in your push-pull cables. Tight bends increase friction very significantly.

Regards, Neil Tucson, AZ
 
Markus,
I had the same problem after several years. As you said disconnect the cables at the trans and check resistance. I found most of the resistance in the RBT itself. There are 3 holes in the Olthoff mechanism. I found a fair improvement by connecting the cable end lower on the Olthoff lever. I went from the top hole to the middle one.
 

john bach

GT40s Supporter
noticed this myself. hard to shift so bought Olthoff shifter thing. no difference. so i'll try different hole as noted above. maybe its a matter of leverage. hard shifting or not the car is still a joy to drive. especially 101 to 118 to 405 to 14 to Willow Springs. has anyone tried adding mechanical shift mechanism vs cable shift. one wag said its too much trouble due to difference in car construction. dont think there could be that much difference in SPF construction. and there is an adjustment to linkage factor to consider. or tried paddle shifting and how does paddle shifting work anyway? is it pneumatic or what? and what would it cost?
 
I ordered my SPF Mk1 with RHD and RH shift. I, too, have an RBT. I have enjoyed driving the car for ten years, and the shifting has always been exceptional. Light and positive, like a smooth bolt action on a rifle. The shift is one of the great pleasures I get from driving my GT40.
The RH shift rod goes straight back from the RH shifter directly to the satellite gearchanging box on the RBT/ZF, and I assume this is why the gearchanging process on a RH rod shift GT40 is so faultless. Whether a mechanical shift linkage retrofit is doable in a LHD GT40, I don't know. I do know that the LHD, mechanical linkage, center shift in the Panteras I have owned was never as good as my GT40, even when the shift linkage was carefully adjusted and optimized.
 

Markus

SPRF40
Lifetime Supporter
Markus,
I had the same problem after several years. As you said disconnect the cables at the trans and check resistance. I found most of the resistance in the RBT itself. There are 3 holes in the Olthoff mechanism. I found a fair improvement by connecting the cable end lower on the Olthoff lever. I went from the top hole to the middle one.


Thanks all for your feedback.
@ Dave, you are correct - But I only have two holes (see picture).
Question: to reduce the force I need to extend the lever - so I would change to the outer hole?!
After you changed the hole - was there the need to adjust the cables?

Markus
 

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Thanks all for your feedback.
@ Dave, you are correct - But I only have two holes (see picture).
Question: to reduce the force I need to extend the lever - so I would change to the outer hole?!
After you changed the hole - was there the need to adjust the cables?

Markus
Markus,
I moved from the outer hole to the middle hole on mine. It's counter intuitive because you would think it would increase the force required, but I found it reduced the movement and some of the resistance. I didn't need to adjust the cable. You're already in the hole I recommended. As I said most of the resistance seemed to be in the RBT itself. Maybe it's worth opening the linkage box on the side of the trans?
 
After putting up with very heavy shifting for years I finally pulled the cables out and found them to be the problem. Almost impossible to move them by hand. The car was well out of warranty by the time I got it running. I started building a rod shifter but the project is currently stalled. As this is keeping me from driving the car I looking for suggestions for a supplier for some good shifter cables. For some reason there is a 4th picture that shows up if you view them. The 4 picture is not mine!
 

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Last edited:
Thanks Neil I'll give them a call. I have a ZFQ transaxle and a Olthoff shifter upgrade. The cable that goes over the top always seemed 2 or so inches to short and the geometry of the shifter arm a little off because of it. Thanks again.
 

Markus

SPRF40
Lifetime Supporter
Some update:

After disconnecting the cables from shifter and gearbox I found the major resistance in the cables itself > so lubrication of the cables was the main task.
Nevertheless I also looked into other topics:

1. Routing of the cables
- Overall Routing seems to be OK for LHD car - you allways have to go from the middle of the car around the engine!!
- lateral cable so far so good – I probably should add a temp protection under the exhaust!
- the other cable is touching the engine block and the outer liner is already melted (to fix this I guess the cable should be longer!?) – see also pics.
Shift cable touches the block 1.JPG
Shift cable touches the block 2.JPG


2. Shifter:
- Not much – regreased the big ball in the plastic and other movable parts
- also found the setup slopy > see related thread: https://www.gt40s.com/threads/spf-shifter-slop.29494/
- I fixed this with a fiberglas “washer” on top of the white plasic

3. Transmission:
- there is some resistance > but I don’t think I can do a lot there!?
- I took some excessive grease from inside the shifter housing and reapplied it to the moving part inside the housing


Lubrication of the cables:

I tried to us a cable oiler like this https://www.amazon.com/Motion-Pro-08-0182-Cable-Luber/dp/B0012TYX9W but I was not satisfied with the result – the device did not fit the size of the shift cable and I had to modify it make work somehow.
I did this with the lateral cable which I took out of the shifter housing to do this – after half a rattle can of “cable” lubricant went in the moving was much better.

I wanted to also lube the other cable without taking everything apart (this cable was not as heavy than the lateral one)

For this used a similar approach like in this video https://www.youtube.com/watch?v=ksiQIvNIPRw unfortunately I did not take pictures.

- I was too lazy to take everything appart
- Therfore I did not take the cable out of the fixation in the car.
- I took a proper size hose and cut it open
- Then I put it over the shift cable and secured it with a hose clamp.
- Then I put the spraying nozzle/tubing from the lubricant into the unsecured hose and secured that with a second hose clamp to seal it some what
- The setup was good enough to force enough lubricant inside to also improve the resistance of the cable operation.

If somebody wants some visual I can try make a sketch or something....

Thanks for all tips and help provided to me.

Currently shifting is better but not like described by Jack Dunn above :(

Markus
 
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