jkruss82

Two fairly quick and easy checks and repairs would be checking the range shift cylinder o-rings. #1 in the picture could be your culprit for jump out of low range, if you have oil in this cylinder you definitely have a bad seal. Secondly, check the yoke bolt is tight on the back of the transmission.

Mack has always offered a shiftable multispeed reverse. Below sales specs are the latest models from about 2000-present. Pre-2000 models were T200s with similar 'M' to designate multi-speed revers. T-310M 1361311 9-29-05.pdf T-310MLR 1361313 9-26-05.pdf TM-308M 1361324.pdf TM-309M 1361325 9-26-05.pdf

The gears are there because that is how a compound range transmission is designed. All the High Range gears (Direct drive through the range) get a Low Range (approx 4 to 1 reduction). The multi speed reverse was designed as an 8 speed with 2 hole/low speed gears. Additionally you can use all 6 speeds ratio's in reverse You will not damage the transmission by using them, but you will have difficulty using them in a practice, because the hole gears are not meant to be shifted thru in high range, they are meant only for low speed use.

200 rpms is either direction when splitting. If at 1600 revs you want to split down: hit the button down, then you need to tap the throttle, let off to break torque, then throttle up to 1800. I'd say that 1600 is a little high to be down splitting, but can't say for sure what you are trying to do.

Pretty big undertaking. Special transmission wire harness, and engine wire harnesses needed. Does the donor chassis have the same engine type as your RD, then maybe you could just pull the donor ECM. Not sure about component shop flashing new software. Flywheel housing should be the same, but flywheel needs swapped out and you need the spacer ring. Allisons are very heavy and require rear buggy spring mounts at the rear of the transmission, so you probably need to fabricate brackets on your frame. I'm not familiar with where the RD rear engine mounts are located (Flywheel Housing or Side of transmission) in either case they will not likely be the same. There would probably be more headaches along the way, that I'm not thinking of. Hate to say this, but I'd recommend trading your truck to get the transmission you want. Pic of buggy spring

Its a 425HP engine. 338 may be the hp at 2100 RPM, but max hp is around 1600-1700 RPM.

Forward 6+2 1 2 3 4 5 6 7 8 17.77 10.94 6.57 4.05 2.54 1.57 1.00 0.71 Reverse 15.59 9.60 6.02 3.73 2.37 1.69

You can probably make this work as long as you pay close attention to plumbing the correct air and oil lines. You will also need to be careful with driveshaft angles, since the input and output shafts have a pretty large offset. Also there were lots of different HI and LO ratios available on these units. for example TC15 LO-2.59 HI-1.00 and TC25 LO-2.59 HI-1.36 Good luck if you try this.

Recommend checking air pressure on both sides of the shift cylinder and shift between Hi and Lo, and do this with a warm transmission if possible. Its possibly you just need some seals I've generally heard that the shifting gets better on a warm trans, but in your case the opposite could possibly be true.

If its the splitter, its the top cover on the back box that possibly needs to have the air cylinder rebuilt (new o-rings, maybe new brass air fittings) and check the air lines and other fittings on top of the transmission.

Unfortunately Australia tightened up their noise regulations and Mack dropped their manuals from being offered about 6 years ago. I think you may be able to special request one, but I would hate to know the cost. In the USA Mack sells mDrive, Allison, Eaton, and Mack T300. About 20% of trucks still have a stick, the other 80% do not and that number continues to grow.

The Mack 6 speed is gone from production. It was nice and lightweight for a class 8 truck, but drive-ability and reliability not so great. Mack's manual transmission take rate is about 10% of new trucks. Mack has the most PTO options available and a 10 speeed multi-speed reverse (T310M) that is shiftable through 6 reverse gears. Otherwise Mack and Eaton match up pretty close with 9/10/13/18 speeds.

it may be for flywheel PTO New Picture.bmp

Sounds like it may need new seals and o-rings if the air lines are all still connected properly.