My 1979 BB512 is in the shop for an engine out service and a problem with the transmission that may involve replacing the pinion and ring gear. Will not know until we get the engine and transmission split. To me one of the bigger differences in performance of the BB512 and the 365GT4BB is in the gearing. The 512BB has longer legs (higher gearing) but in reality in the USA is very difficult to use. I looked at the manuals and the gearing. The ratio of 512BB gear ratios divided by 365GT4BB is 95.62 % throughout all gears. This suggests that you can put in the pinion and ring from a 365GT4BB and lower the ratio's. Some people have done this with Daytona's as well to make them more drivable. I may consider this if we have to go to a new pinion and ring for my 512BB. Has anyone ever done this? What are owners thoughts aside from the originality question, which I admit is an issue for me. I love my car but think it would benefit form shorter legs. Appreciate you opinions. Drew Altemara
I think its a great idea, 3rd gear is all it takes for freeway driving now in these cars 4th and 5th a waste, if it could top out at 140-150 at redline you'd have a screamer. The only concern would be the quill shaft as you could burn rubber so easily by nailing the throttle. For the price of a new pinon and ring from Ferrari you could have a custom one made easily from a race shop for 1/2 the price, more than likely your ring and pinion can be polished up and saved though. Here's a company I found with a quick search that does reverse engineering http://www.specialtygear.com/
Or it can be done by changing the ratio of the drop gears. I'd like to shorten the legs a little as well. Carobu quoted about $3500 for a set of drop gears, although straight cut, which might be too noisy.
The lower numerical ratio in the 512's was to compensate for the lower redline of the engine as well as take advantage of the extra torque of the larger engine. Im not concerned about toping out a touch lower to get the bottom end grunt so I would take the opportunity to make the change now. I would also think the higher numerical ratio would decrease load on the quill shaft because the effort from the engine would be lower to move the weight of the car. Make sense?
mike sheehan has been telling me to get short gears cut for my boxer for years. you should call him to ask if he has any real specs to go by. he did say the bbi is like an f-14 when the gears are cut.
Straight cut supposedly gives more power, as opposed to changing the pinion the transfer gears would be an easy swap. With all the noise the carb Bbs make I doubt you'll hear the xtra gear whine unless putting down the freeway. Does anyone know if their is anything special about the pinions and gears in Ferraris concerning forged metal or special machining techniques? I have heard the Roloefs(sp?) aftermarket pinons used in Daytonas just are not as good as OEM Ferrari parts and have a tendency to fail.
john, square cut gears sound out of this world! boy the trans am and gto racecars make the most unreal sound w/ the gear whine when combined w/ the engine note!!!
Helical cut drop gears would be great but the straight cut ones would sound like crap on a street car and get tiring after a while. If you think a tubi is loud and irritating on trips then forget about straight cut gears. Good point on the failures in the daytonas, I would want to have someone like richmond or precision gear make a set. Im sure they could given the specs and with 2500HP cars using them im sure they would be up to the task.
Thanks for the replies. Could you explain drop gears and why changing to a set of shorter drop gears (assume not stratght cut as I do not think I want any more noise) would be better than just changing over to a 365GT4BB pinion and ring set up?
I thought you gentlemen might enjoy looking at what happened to cause the problem. 5mph, making a left turn from a stop sign, car totally warmed up. Side differential carrier failed. The piece that broke off was laying at the bottom of the differential. Looking through the differential drain hole there appears to be some minor markings on the ring gear. Will have to wait until the transmission and engine are split to see what the damage is. maybe they can just be polished, maybe not. Can you say ouch! Drew Image Unavailable, Please Login
The gears that transfer the input shaft torque to the gearbox at the rear of the bellhousing are the drop gears or transfer gears. Changing the ratio between the input and the gearbox is like changing the final drive ratio and less expensive also its a walk in the park to do. It is a method employed by cars used on different tracks needing different gearing and can be looked at as a quick change rear end - same advantage.
I just talked with Caribou Engineering and they said they have only made drop gears for the F40. Has anyone ever had drop gears cut for a 512 BB? thanks! John
I had let some gears for my koenig competition about 4 years ago have a look here at post no. 153 http://www.ferrarichat.com/forum/boxers-tr-m/192826-koenig-competition-1-000-hp-3.html but you see, the gears are straight toothed gears and not like the original helical gears
Newman diff carrier and different drop gears, sounds like a perfect mod. Did Trs have the same gears ratios as 512 Bb and BBis. Whats the redline of a Tr and an M motor.
I could have them made. I have a shop I use to for making transmission parts and they're currently making me a gearbox shaft for a lamborghini thats NLA. I suspect my BB has Koenig drop gears in it which I could use as samples when I take my car apart. Ferrari did change the input shaft part way through the BB512 production to accept a 3rd bearing support in the drop gear case but not sure if the gears are any different but something to keep in mind when getting different gears.
