Alison 545

[CAJUNCUMMIN]

Allison 545

I spoke to a gentle man to night that put a 545 on a 5. 9, said the ratio was to low but with a gear venders overdrive it was close to the dodge transmission but with more pulling capability, has any one else familure with the 545, is it a heavier duty transmission and how does it perform,will I sacrifice excelleration for towing power.

 

[Bob Beauchaine]

I looked into the Allison MT545 almost 8 years ago as a mate for the B5. 9 in another application. It was rated at 300hp and 650lb ft torque. It should work well with a first gen truck. Keep in mind that it has no park capabilities so you would probably have to use a micro lock to set the rear brakes. I don't know if they will work with anti-lock rear brakes. I researched this through Cummins so I know it can be mated to our engines.

Hope this helps.

Happy Trails.

 

[bigkid59]

The AT series Allison will handle a lot of torque very well. The main disadvantages are size and weight. The transmission is large enough that you will most likely have to modify your cab floor. The weight will not be a problem unless you are already experiencing front end sag.



Another disadvantage is that the AT series does not offer a lockup convertor. The convertor is available in several model numbers depending on intended use. One for a low torque engine, such as a gas burner or a diesel such as a 9. 0 liter IH, would have more stall speed than one intended for a high torque engine.



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. I have an AT540 with that arraingement and it is fairly common to find these models.



First gear in these transmissions is a low ratio that will help in getting a load started without needing low ratio axle gears. The problem is that although the transmission is a 4 speed fourth gear is not an overdrive ratio. This could be overcome with an overdrive unit.



All in all, the AT series will work but not without some fabrication. You will also need an SAE type engine adapter and the proper flywheel, all of which can be obtained from an Allison distributor. Having bought some of this stuff in the past, let me tell you to be sitting down when you price the parts. Finding a salvage mid size truck with a B series engine and an Allison transmission would make things much simpler and more economical.



Good luck with the project if you undertake doing it!

 

[CAJUNCUMMIN]

I have located a AT545 that had been on a 5. 9, I just need to find a Gear Venders overdrive. Do any of the after market tc manufactures offer tc,s for the AT545.

 

[HoleshotHolset]

Sounds as if many have contemplated this swap... .

In a perfect world... . 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. We all know this is not possible, so we look to other solutions..... these other solutions include the offerings from GM and Ford and of course the GM subsidiary Allison.

The 4L80-E and E4OD are good, but still have similar problem areas as the 47RE/H. The Allisons that do have OD also suffer in similar ways. The BIG Allisons also would suck a ton of HP... just from turning the transmission itself over... nevermind the already killer drivetrain loss. 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... . pulling hills at highway speed with a trailer and a bombed diesel means eventual failure. The Gear Vendors OD unit also has it's flaws... .....

I'd almost be perfectly happy with a transmission that I had to pull every year or every other year that could handle a HEAVILY bombed 6BTA (600rwhp) with some sort of reliability. Is this plausible?



Matt - in search of the perfect auto transmission

 

[pcorssmit]

Other ways to overcome the OD problem would be to run higher gears or a medium duty auxilary trans. There was a guy on here that had a 4 speed Allison w/ a 3 spd Brown-Lipe auxiliary, username was LARGE CAR, but I don't think he's here anymore.



Pete

 

[HoleshotHolset]

I have considered running higher gears, but that still does not allow me to run overdrive with confidence that it's going to hold together at higher levels of BOMBing...

I'd like to hear more about the Allison/3-spd OD unit... . sounds beefy enough.....



Matt

 

[Strick-9]

Matt,



I don't have 600 rwhp, but I've been through my share of transmission trouble. When my transmission was rebuilt in February, I told myself I would be happy if it only lasted 6 months.



Well, I'm on my 7th month now and there are no signs of failure. I burnt the clutches several times bad enough for the smell to come in the cab. That was before I got my pressures dialed in to where they are now and tapered my fueling to match.



If you don't intentionally hurt your transmission and you are willing to learn how and why things work, your transmission will handle quite a bit of power.



-Chris

 

[HoleshotHolset]

I suppose WHENI am at 600rwhp getting even 6 months out of a transmission is reasonable. I've heard that anything above 350rwhp (even with transmission mods... ) is complete abuse to your transmission.

I try to drive with my head screwed on straight... but the temptation to drag race it is overwhelming!



Matt

addendum: Okay, you have the 91% TC and 85PSI VB... . I'm looking for the most balls-to-the-wall parts that DTT has to offer and this seems pretty close. Shift harshness isn't really an issue... I just want it to last a while.