pulling hills at highway speed with a trailer and a bombed diesel means eventual failure. It kills me knowing that the only auto trannies with OD that fit the size/weight criteria are not meant to handle a lot of HP/torque while in overdrive. nevermind the already killer drivetrain loss. just from turning the transmission itself over. The BIG Allisons also would suck a ton of HP. The Allisons that do have OD also suffer in similar ways. The 4L80-E and E4OD are good, but still have similar problem areas as the 47RE/H. these other solutions include the offerings from GM and Ford and of course the GM subsidiary Allison. We all know this is not possible, so we look to other solutions. my auto transmission would bolt up to my 6BTA, weigh the same or less as my OEM 47RH, and have a comparable overdrive final ratio. Sounds as if many have contemplated this swap. Good luck with the project if you undertake doing it! Finding a salvage mid size truck with a B series engine and an Allison transmission would make things much simpler and more economical. Having bought some of this stuff in the past, let me tell you to be sitting down when you price the parts. You will also need an SAE type engine adapter and the proper flywheel, all of which can be obtained from an Allison distributor. This could be overcome with an overdrive unit.Īll in all, the AT series will work but not without some fabrication. The problem is that although the transmission is a 4 speed fourth gear is not an overdrive ratio. I have an AT540 with that arraingement and it is fairly common to find these models.įirst gear in these transmissions is a low ratio that will help in getting a load started without needing low ratio axle gears. The lack of a park position is most easily managed by using a transmission with the parking brake mounted on the transmission tailshaft housing and applying braking force to the driveshaft. 0 liter IH, would have more stall speed than one intended for a high torque engine. One for a low torque engine, such as a gas burner or a diesel such as a 9. The convertor is available in several model numbers depending on intended use. The weight will not be a problem unless you are already experiencing front end sag.Īnother disadvantage is that the AT series does not offer a lockup convertor. The transmission is large enough that you will most likely have to modify your cab floor. The main disadvantages are size and weight. The AT series Allison will handle a lot of torque very well.
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