Join in and discuss all the action for the 2012 San Felipe 250. Robby Gordon will drive the #77 SPEED Energy Trophy Truck. Live coverage begins on Saturday, March 10th via the SAN FELIPE link on the main menu. Trophy Trucks are slated to begin at 1:00pm/et ( 10:00am local time ) .Raceday chat will begin at 9:00am/et. Robby Gordon will start 3rd.
Yes the standard trans used in most TT's is the GM Turbo 400. The difference between a T400 and a gear box like a Albins, Fortin or Xtrac is those are going to be a manual sequential type trans. More of a true gearbox vs a over built automatic transmission with a modified manual shift valve body. Heat is the killer to any automatic transmission as fluid is what drives the transmission. For those who do not know a automatic transmission does not use gears. They use fluid to push valves open and close, which intern engages clutches. The friction clutches is what transfers the power to the rear axle and to the ground. The only gear your able to change gear ratios with is the rear axle ring & pinion gear. An actual gear box uses gears which can be changed thus allowing the option to use much larger rear axle gears. We have all heard RG talk about the large tires being hard on the rear gears. You hear all the time at the Baja 1000 about a team being down due to changing a rear gear. It has happened to RG many times. They lost a Baja 1000 one time as they broke a rear gear while having a huge lead and the crew could not get to them for hours. Also a gear box stays much cooler as the fluid is not what drives the transmission. These style gear boxes would be a sequential gear stack and would only need a clutch to be used when you first take off. After that you just change gears as needed.
The best way to explain this is the transaxle is based off of what VW did with the bug and VW bus. You can build them up with all the best parts, but you are still limited to what parts can fit, as you are using a design that was built in the 50's & 60's for 40 hp, Not 250+ hp. In the 80's companies like Fortin saw the need to take the transaxle concept but build it so that the state of the art (for it time) Porsche engines would not brake them. Years later companies like Mendeola, Albins, PBS and others have formed. Its these companies that have allowed 700 hp V8's enter the buggy classes. You dont hear about the class 1, class 10 and class 12 cars having trans issues like they used to.
Like you said the T400 was designed a century ago and its tough to improve such an old design. You can only do so mush with the same concept. The T400 was not designed for 800 hp trucks blasting through the desert. The automatic trans is probably the weakest link in the TT class. I believe the transmissions in both buggy's and tracks have been the slowest to evolve and have held back the technology in this sport. Can you imagine if we were still using shock technology from 20 years ago? Heck even 5 to 10 years ago! The trans technology in the buggy's classes has out paced the truck classes. I truly believe these Xtrac, Fortin TT, and Albins gearboxes will be the future of the TT class.
Despite the 400 being "old" technology, a manual type of gearbox is even older technology. Lets see, RG going down a bumpy or smooth desert road at 100mph+, that 400 would be in 3rd, being the "direct" gear, 1:1. That means the whole internal geartrain is a one solid rotating ( at engine rpm) piece, creating not much heat. even the TC is barely slipping, rotating several 1000 rpm over stall. That Non-Locked TC, all the time, acts like a shock absorber for the internal geartrain. Iam not sure a solid non-slipping clutch would hold either with those huge tires. Just listen at the hummer at those on-off throttle transitions, you can hear the torsion in the system, being that on-off type engine sound. It would be a smooth sound with a TC. Maybe an Albins with a TC would be the best combo.
T400's do have use planetary gear sets for the tranmission ratios. The Albin is a dog box.
sorry for the insight GTX.
Mike you are correct about the plantary gears, I wasn't thinking about that. But my understanding is that the choices do not allow the bigger rear end gear that a gearbox would allow. Fortin and a few have designed a planetary gear reduction unit that bolts to the rear of the auto trans. I know Pistol and a few others have used this to help with the larger tires and gear.
@Nikal , do you know who makes off road (Robby's) v drive units?I'm thinking the final drive ratio could be made in the v-drive case with the spur gears like a quick change rear end. Or maybe it needs to be a transfer case (with out the angle)
thankx NIKAL great insight.
ditto X 2
is the truck still a v-drive setup?
Yes, same as it was when it was built
Mike, I thought TOG said earlier that Robby was going to an Albins gearbox? isn't that what is run in the Hummers? I realize the Hummer gear boxes are trans axels and this would not be the same case with the TT. One thing I have read about and was mentioned by rednecktech is an Albins style box with a torque converter which helps to cushion the hit's on the drive train I have no idea how this works. I hate to admit I have no real understanding of how a torque converter works not looking for a tutorial just wonder if that type of gear box could be a plus in the TT.... Not just directing this to Mike any of you with Knowlage on this subject your input would be greatly appriciated, Thank's
Wally ,I'll PM you . Since GTX called me a know it all.