Renshift, Springs Options

[J P Stein]

Our AX this last Sunday had a curving 3rd gear blast that really got ones attention (IMG:style_emoticons/default/w00t.gif).....the car would really move around on that rough surface.... followed by a square corner that required all the brakes and a downshift to second. While thrashing my car, old Chuck made his best attempt to get it into reverse (down shifting/braking at turn in to kick the back end around....ones plate is full (IMG:style_emoticons/default/biggrin.gif) )......I could hear the grind from 200 yards away.........AAAUUUGGHH.

Oh well (IMG:style_emoticons/default/confused24.gif) he was fast.

[Randal]

why don't you try some of james' nylon or solid motor mounts?

Gottem (SMM)!

All the potentially movable parts are either solid, new or recently rebuilt. Brad can verify.

I'll bet the issue is corning loads, which we've essentially been increasing as we've modified the car during the last 4 events.

During the time of the last 4 event we've added adjustable high performace Koni's in the back, a Smart Racing Product ASW in the front, 250# springs in the back and new sticky slicks.

And of course as the car handles better - it is being driven faster with increased cornering load.

I'm putting in the new 12lb. RennShift springs tonight. If they don't keep me straight, then we'll figure out what is next with RennShift.

Hey, anyone out there got 24lb springs? (IMG:style_emoticons/default/biggrin.gif)

[Jeroen]

I most think it's most likely the driver and nothing mechanical
When you're shifting under heavy side loads, your shifting movement will be off because the sideloading will make your body move, so you're basically pushing or pulling the shiftlever sideways (you may not even be aware of it)

Hopefully the stiffer springs in the rennshift will solve it.
You could also try moving your seat a little more forward or upright

cheers,

Jeroen

[Brad Roberts]

Randal is 6'1 200+ lbs.. we dont have much room to move his seat. I told him the same thing... I figured his arm weight is helping to move the shifter when he has to shift in the middle of a corner. He has also had issues nicking reverse when making the 1-2 upshift with one hand on the wheel and one on the shifter.

Something I will do before the next event is install a modified shift rod. His rod going through the rear shift console bushing is loose (even though it has a new bushing with a thinner inside diameter hole) We are losing side to side motion in that bushing. The front to back motion is not affected.


B

[Randal]

modified shift rod

Guess it had to happen sooner or later.

[Brad Roberts]

I want to weld one up and machine it down so it fits that shift console bushing perfectly. The ideal situation would be to run a heim joint there and let the rod slide through it. This would give us PRECISE shift rod action.

The other way to do it... something I have never posted...

Extend the shift rod to another bushing in line with the one in the stock location. This would support the shaft in two area's instead of one. Hard to describe, but it would require tig welding a piece from a old broken shift console to your new one and extending the shift rod through a second bushing.


B

[drew365]

I have one spot at Willow Springs small track that I have to shift under heavy side load from 2nd to 3rd and the trans either will crunch or not engage. I'm certain that it's caused by flexing on my tub. I plan on connecting my roll cage to the rear shock towers and possibly the shock towers to the top of the tranny mounts, in the near future. If that doesn't work I may fire the driver. (IMG:style_emoticons/default/smile.gif)

[Randal]

Brad.

So this sounds like you need the car? Marina is coming up soon, so tell me the date.

BTW will this eliminate the lack of engagement feeling that happens when you engage 2nd standing still? Ugh, does that make sense?

[Randal]

Progress!

The new 8" steel shifter rod is being machined as we speak.

It will be machined to fit tight in the bushing. We will alter the bushing a bit, so it slides, when we get ready to weld the rod on to the rest of the shifting rod/ lever, fork or whatever that call it.

[maf914]

I want to weld one up and machine it down so it fits that shift console bushing perfectly. The ideal situation would be to run a heim joint there and let the rod slide through it. This would give us PRECISE shift rod action.

I purchased a bronze bushing (the type held by a c-clip) from the bird and found that the inside diameter was about the same as the stock plastic bushing and the shift rod still had plenty of loose play. Like the plastic bushing the inner diameter of the bronze busing appears to be tapered, i.e. the inner diameter is larger at one end than the other.

I went to a local hobby shop and bought a piece of brass tubing that fit smoothly over the machined end of the shift rod where it rides in the busing. This was to be used to sleeve the bushing down to match the shift rod. I took the brass bushing and tinned the inner surface with solder. I cut a piece of the brass tubing the same length as the bushing and placed it inside the bushing. It was almost a perfect interference fit. I cleaned both pieces, added flux, hit it with the propane torch, added a bit of solder, polished it up and now have a bushing that is a fairly snug fit. The bad news is it is not yet installed, but I hope it works well. I'm concerned about possible binding though. Just in case I have a new plastic bushing standing by.

After doing this, it occurred to me that the shift rod itself could be sleeved with either a brass or other metal tube to achieve the same thing, a rod and bushing combination that fit with less play. This sleeve could be epoxied onto the shift rod which means it could be ground off if necessary. Then either the plastic or bronze bushing could be used with a snug fit.

[Randal]

I'm using solid motor mounts and nylon bushings.

What we're doing now:

Changing to the 12lb springs.

Building a new shift rod end, that will be very tight to the nylon bushing.

[Dave_Darling]

The other way to do it... something I have never posted...

Extend the shift rod to another bushing in line with the one in the stock location.

I've seen pics of that, somewhere... Someone's race car, but I don't remember whose or where I saw the pics.

--DD

[Randal]

I've seen pics of that, somewhere...

Come on Dave, you've got to remember! (IMG:style_emoticons/default/clap56.gif)

[JWest]

I've seen pics of that, somewhere... Someone's race car, but I don't remember whose or where I saw the pics.

--DD

Yeah, I've seen that too. Maybe the other Brumos car (one had a Hewland) or another historical GT.

You have to be careful taking out the bushing slop, as at some point the linkage will bind up. It is not a perfectly aligned system. Adding another support and an extra u-joint would perfect it, but unfortunately will only make it incrementally better for a lot of work.

I may try it anyway... (IMG:style_emoticons/default/wacko.gif)

[Randal]

Great Customer Service!

Thanks James for re-building my Rennshift and getting it back so quickly.

Randal