ALFAGTV6.COM

Doesn't Greg mean that the pinion gear breaks off the shaft perhaps?

I remember a posting by Barry about problems with high power transaxles and breaking the shaft right after the pinionwheel was one of the problems if i recall correctly.

Do you maintain the silly little Alfa Romeo input shaft splines or do you change to something much more readily available?

The basic kits are straight replacement parts, if you want a differrent input spline it can be produced but its not off the shelf.

I have never had a problem with the input spline, and I havent come ocross the pinion breaking. i have seen alot of pinions mashing and cracking the crown due to either flex causing misallignment, bad shimming or other failures elsewhere in the driveline causing abrubt locking.

You can get the clutch input twisting and various other failures but at the end of the day it is what it is and driver abuse is more the cause than any inherent weakness. The driveline is like a pair of gyroscopes held between a flexing bar so any abrubt change in alignment can have a major effect. hence the clutch housing failures.

I'm not re-inventing the wheel, neither do I feel the need to. I have two ex-works Alffetta that I am restoring and the kits, props,housing etc are a biproduct of rebuilding these cars to their correct historic spec.

Hopefully a few people might be helped in their projects as I found it very difficult to source the correct parts myself.

These new parts look great. I am was just pointing out that I have seen pinon gears break in both GTV6s and once in a Milano, so I know those fail and it wasn't due to abuse or improper assembly. Barry ran into the same issues. That said, I think the new parts in the thread look awesome!


Greg,
www.hiperformancestore.com
www.okinjectors.com

sorry greg i wasnt trying to be argumentative

I would be interested to know which ratio pinion they were using. Its hard to see the main shaft breaking, I just havent seen one break like that, I do modify the case to run a needle roller on the main end but generally the 11/43 and the 10/41 are pretty good and less so the 10/43 due to the smaller pinion head.
I looked into producing main shafts and crown wheels but the cost is just too high to justify, I would need to produce maybe 100 to bring the cost into a reachable level and invest £50-60,000, a one off would cost £2-3000.
I will post some Pics of the dogbox kit later this week

No Problem,

I have seen two pinion gears break in 1983 GTV6 boxes which are 3.42, and one Milano 4.10 pinion gear break. All broke in the exact same way, the teeth broke off. One broke in a completely stock engine, two on supercharged engines. I am not really sure, but I think it's quite possible your gears will help the pinion gear because there is no fore/aft force on the pinion shaft with straight cut gears. I am following this with interest. With the new Sprintex supercharger, 400-500hp is almost a piece of cake with the 12 valve 3.0. I will produce the kit if there is a way to make the transaxle and driveline handle it.

Greg

A friend of mine broke the pinion on his 75 TS gearbox. It was used with Tutela gearbox oil (don't remember the name, it was for limited slip and hypoid gears though). He never had a problem in road use, but after some hard laps at a local circuit, about five, he started hearing a whining noise and couldn't engage fifth gear. He ended up tearing up the gearbox apart and finding the pinion gear missing a few teeth. Upon examination of the parts we found evidence of heat on the broken parts. We think that the heat generated from the rear brakes transfered through the splines to the crown and pinion, and the case, maybe causing a slight missalignment due to heat deformation where both bearings are placed that the crown spins on. Better oil and case temperature control might be a very good way and not too expensive, to increase the amount of power these transaxles can stand. The TS engine is std.

Yep , Fed your mate made the same mistake as me . When you hear the whining in diff that's when you know you have the WRONG oil . That oil was not an EP the molecules were totally shearing . My gearbox did not even have to get hot to do that but it only occurred on the track even though it was fine for 200 km of road driving .

Yes, he was using that oil for years though, but just started doing a few trackdays, it happened on 5 really hot laps in a 3km track with tight turns and lot of braking, so it all adds up really to being an oil quality and temperature thing. They are not the strongest gearboxes but without thrashing them, using the correct high quality gearbox oil and good temperature control for track use it should cope pretty well, how much power are you making at the wheels Kev?

Fed , I swear by the Redline 75w90ns Oil . My car makes a whopping 192kw on the wheels at 6000ft (3.7 24v) . I rarely use second gear . I think as Alfetta discussed with his mods theses boxes should be bullet proof .

I appreciate the vote of confidence

First thing I wanted to mention was that yes heat is a real issue and one of the best things you can do is reduce the heat transfer form the brakes or cool the gearbox. so If you dont have a problem shifting your brakes outboard I would do it and fit an electric scavenge pump to an oilcooler. If you cant move your discs fit an oilcooler and pipe some air to your brakes. i was looking at an ex-works Francia and Shlesser 75 turbo (actually buying a group A turbo engine) it had a colloti dog box, outboard brakes and an oil cooler, it ran 400bhp all day long so maybe they did know something about race cars!?
I also have a friend who runs a GTV6 with a 24v 3.8l with a solid prop, one of the first batches of re-inforced clutch housings and a straight-toothed box (of 80's vintage) it runs over 400bhp on a 11/43 diff so the system can cope.
Dog box wise I have a set testing in a 75 3.0l 24v race car but its not done any hard track time so I'm not convinced the standard selectors or strong enough for the shock loadings but nothings broken yet so I'm pretty optomistic and have been assured by my gearbox guys that the standard Alfetta selector is man enough.

I do believe that just the swap to needle rollers throughout the box does assist with the boxes ability to handle power, the reduction in transmission losses means less heat and less stress.

Well, seems you've done what we thought of doing, fitting needle roller bearings instead of the bronze bearings to reduce friction and thus heat. I'm starting to think these gearboxes are man enough to handle good power, you just need to upgrade it to cope with the extra heat.

Kev, sadly the redline oil was available in Argentina (as the closest place to get it at reasonable price, maybe should try Brasil), but give their current import restrictions i'm mostly positive they are out of it. We are using Motul here now, with the EP additive, and cooling ducts for the rear brakes to try and control the gearbox temperature on the short stints.
I'm finishing up the Giulietta racer but it has the small 1.6 right now until I rebuild the Twin Spark engine and turbo it, so I don't expect any problems other than using good oil and cooling for the rear brakes as the 1.6 engine doesn't have much power. Talking about it, that's a very nice power figure for 6000ft, what's the sea level correction?

Sea level correction is between 15-18 percent . As most know I do run Mocul diff cooler , outboard brakes , (md style reinforced clutch housing ) but standard prop with cages to absorb shock . I also have a gripper LS which also plays a part .