Hi guys

For those that don't know me, I rally a 914-4 1973 in historic rallying over here in the UK. I've gone through 2 rear ball cup linkage things in the past 2 years. The latest failure (today) forced us to retire from this weekends rally, a real dissapointment as we were really peddling fast.

I've got a full on Rennshift system, so the only non bronze bushing between the bottom of the shifter and the shifter fork on the gearbox is the plastic ball cup thing at the rear (kinda the weak link). The previous one that I replaced last year was a new one at the start of the year, but by the end of the season it had cracks on it in the usual places and was ready to let go. I then put on a good secondhand one I had lying about, which completely disintegrated today, which meant I couldn't get it into any gear - rally over

Another thing to keep in mind hear is that with rallying it ALOT more stressfull on the linkage than any Auto-X or circuit racing due to the amount of shifts e.g. quite often 2 shifts down, 2 shifts back up for every corner, 50 corners per stage, 7 stages per rally. Then throw in dust and dirt constantly at everything that moves and has oil/grease on it, and to make matters worse there's an additional heat issue as we run a big skid-plate on the rear so all that heat from the exhaust has a LOT less air flow to dissapate the heat.

SO what I'm saying is that this plastic part gets a lot of grief, a lot of heat, a lot of dirt. If this part ends up being a throw away part after each rally I can accept that, I was wondering if anyone knows of a bronze version or some other upgrades people have experience with?

Thanks in advance for any pointers

Moggy glad to hear you were peddling fast over there. Is that with your new engine?

Sorry to hear about the issues.

The cup that we use in our road racer is a hard durometer urethane or rubber part. I got two of them from Rennshift. I have no idea if they are O.E. parts, but I do know that they will not crack like a plastic part. I just replaced one at the track last weekend because it picked up a bit of slop. Didn't really cause a problem, I just wanted to tighten up the shifter travel a bit.

I'm not sure how you would be able to make a bronze part work as it has to pop over the ball of the hockey stick and then fit snug. It would likely have to be a two piece part. Did the old cups slide freely in the bucket part that it fits in? If it binds that could easily lead to a failure (but would probably cause stiff shifting).
Maybe James of Rennshift will chime in. He knows these systems better than anyone and can give you good advise. I'd contact him if he doesn't find this thread.
Good luck!
Len

Hi Len

Thanks for you input. Yep that's with the new engine. Fighting with the big boys now Managed to beat a 911 2.7litre RS on the first stage by 20seconds over the 5miles, happy with that Then on the second stage is when the bushing let go so no gears New engine and gearbox are really helping me to drift it through and then out of the corners nicely on the power.

Next rally is in 12 days now so need to sort this out QUICK.

I've found this Poly-graphite version from Weltmeister

http://www.paragon-products.com/product_p/welt_910241.htm

so think I'm going to order 2 of these and 2 of the standard plastic ones (just in case the Poly-graphite ones are even worse than the plastic ones). I hope the poly ones have more durability to the extreme hot/dirt conditions, the plastic ones just don't seem up to the job for my application.

I agree a bronze one would have to be a 2 part unit, now I know it's the same part as that found at the bottom of a 911 shifter maybe someone has made one for this application. I'll keep on browsing, but in the meantime I'm going to order to 2 poly-graphite and 2 plastic ones as time is short.

Cheers

Moggy

I've made a bronze sleeve captured around a spherical bearing for this application (requiring a new link instead of the ball-end) but I was not satisfied with it's longevity and the fact that many cups are corroded and scored inside. I can post a pic if you want to see how it was fabricated.

I don't know why you are experiencing premature failure unless you are bottoming out the bushing the cup, or if your cup is from a 911 and too short.

There is another bushing you can try - the factory cup bushing from an '87 to '89 911 shifter is made from some type of graphite impregnated plastic. I can't comment on it's longevity but it might be worth trying if this is truly a material failure. Porsche part# 911-424-139-01.

Thanks for your input. I've kinda knocked the bronze bush idea on the head, your experience is the last nail in the lid. Good to know at least someone else has already been down that path. I'm going to try the poly-graphite products from Weltmeister and see how I get on. I'm sure they'll have better heat resistant properties than the plastic standard ones. That's basically why I'm experiencing the premature failures. It's the extremely harsh environment I'm putting them under: high heat, constant dirt/dust and heavy use both with me slamming it into gears so often in such a short space of time. You'd be amazed how many times you have to change gear in the heat of battle in a day of rallying

I raced with a Rennshift for years, as a matter of fact I bought one right after they came out and I found I would punish the cup bushing in the rear more than usual. I adjusted my driving style and MADE myself shift easier, even in the Mexican street circuit races I did for years down in Baja MX and not hammer the shifts. One of the things I made sure of was that the stops in the shifter actually stopped the shifting and not the lever at the rear of the transmission. That way no load was put on the lever or at worse it was minimal as I have seen them break right off several times. I would also replace the bushing yearly and it was one of the items I checked before every race along with the cable pulley wheel although I started using one of Patrick MotorSports super high temp wheels and never had a problem after. His wheels were made of a hight temp type of Delrin or something and I know it never gave or moved so making that cup bushing would make it nearly impossible to get the ball into the hole and still have a tight fit.

Do you use the molded factory cover and if not I'd recommend it strongly. I used to wrap my transmission console with header heat wrap tape to help keep exhaust away from it also. Good luck!

Great tip, thanks John
I happen to have extra header wrap and a cover that keeps slipping off and getting burnt

Thanks John, good info, from a man that seems to have got the t-shirt. Once this next rally is over I'm going to heat wrap the header to try to control the heat under there. You can see my main problem below, I've got this big skid plate that doesn't allow much heat to escape and deflects loads back:



I've now got a European Headers system on there but you get the idea. I need to control the heat under there a bit more.

I wasn't aware that the clutch wheel can also fail. What happens? is it a catastrophic fail when it goes or a gradual one? what are the signs to look out for? I'm trying to upgrade everything that could cause another early shower.

Thanks again for your help

Well, the picture explains why things are melting and getting destroyed by excessive heat. The skid plate is probably keeping the hot air from the exhaust right next to the trans and I would bet that during a rally the transmissions gets a tad hard to shift late in a stage? I had that issue with street circuit races in Mexico and finally installed a trans cooler kit from Patrick Motorsports in the Phoenix AZ area and it is equally easy to put one together yourself. Jim also sells a temp insert to replace the speedo drive plug and a very nice VDO gauge that is really handy to have.

In your case I would not wrap the headers but fabricate some aluminum heat shields that curve over the headers to keep heat off the engine and trans parts and possibly add a pair of cooling fans to blow air from the trunk down into that area to help force the heat away. You are a hell of a guy rallying a 914 with the running gear as fragile as it is on our cars!!

John

You read my mind This weekend I fabricated some ally heat shield off the skid plate which curves over the exhaust, this should help some. I also performed some heat tests on the two types of ball cup bush I have, one standard and one poly-graphite, the poly-graphite one has a MUCH higher resistance to direct & radiant heat. Kinda thought that would be the results but always nice to see with my own eyes.

The oil temp in the speedo drive is a good idea, apart from the fact I need the speedo drive to drive the trip. I'm assuming it replaces the speedo drive? How does the oil get pumped around with a gearbox oil cooler. I have a spare Mocal oil cooler knocking about so wouldn't mind knowing the constituent parts to a system. Where do people tap off?

RE the weak running gear - the front is the same as a 911, I don't see this as weak. The rear however was a different matter. I've strengthened all around the inner and outer pickups using a great kit from Tangerine Racing, including some bars which go from the inner pickup to the lower firewall. Also had a set of strengthened rear arms from PMB Performance, but not using the usual GT over welded kit, the way he does it keeps the arms about the same weight. I'll take them off the car at the end of the season and put them back on my jig to see if they've moved any - so far so good.

Someone asked why I hadn't got the dust shield thing that goes all around the gear change mechanism at the bottom of the gearbox - it melted

Next rally is this weekend coming

Glad you made the heat shield. If the plastic cover is melting then you definately need a pump/cooler setup. I tapped the drain plug for the suction and then drilled/tapped two holes in the top of the case, one over the gear stack and the other over the R&P. The pump is a gear type and the whole setup allows you to run a full gallon of gear lube which helps. I also replaced the vent fitting with an AN hose that ran to the puke take in the rear trunk. I bought the whole thing as a kit from Jim Patrick which saved me a ton of time and it had everything. Be sure to use the braided Earl's hose due to the high heat area. Here are a couple of picts of the inside of the rear trunk with the setup.

Nice setup John. Good to see something done properly

Couldn't find the gearbox cooler kit on Patrick Motorsport, but did find the Tilton pump you've used. That's the key part for me, everything else I can build the setup around. Have you got any pics of where you've drilled and tapped for the oil lines, don't worry if you haven't... I'll figure it out.

Thanks for all your help John

I drilled on the top of the case near webs but far enough away to allow the fittings to be tightened. You'll have to open out the gear stack and also the R&P so no possibility of chips falling into things. The air inlet line runs from the front side of the right rear flare and has a small boat engine compartment vent axial fan in the line to help with air flow at all times. It had been installed when I took these.

You'll have to call Jim as he has many things not on his web site. He also sells a very good high temp clutch cable wheel that will never melt.

Yes, i can ...
You've been running your cup exposed to the elements. No wonder it's failing ...


When you install the new one, get the stock plastic cover over the rear to keep all the dirt out of there!
Andy

PS: You can see the stock cover here, slightly modified to work with the JWest rear linkage setup.

I feel once he gets the heat away from the rear of the trans so he is not melting the covers that will keep the dirt out and reduce wear for sure.

Thanks all for your help in sorting this. The addition of the heat shield, re-installing the (half melted) dust shield, and using a poly-graphite ball cup bush meant that we finished our first rally of the season this weekend just gone

I've inspected the bush last night and it's as good as the day I bought it so looks like that's a problem nailed.

Next on the list is the clutch wheel which looks like it's melted a little, time to upgrade before it's too late.

Also, had some major dust issues clogging the air filters (as you can see from the pics below) which caused loss of power on the last few stages. Nevertheless we still managed a respectable 4th in class against some much more powerfull competition.

Here's some pics to show you what we got up to, I've got some great in car footage too once I figure out how to upload a 14minute 2Gb AVI file up to Youtube.

Cheers

Moggy






Got a tarmac event next so it's all change to the setup again now

Gooooooood looking car! I don't think my race car ever got that dusty and I used to cringe if I even got any rubber streaks on the hood! Anyways, I would recommend trying some spacers under the rear of the roof to raise it up about an inch to inch and a half. That will do two things, one it will let more air in from the front to help keep you cooler and second is it will break the vacuum behind the rear window and let more air into the engine compartment to help the engine.