I have been surfing around the net looking for a medium duty truck. My preference would be a four door FL70 with an 8.3 backed up by a nine or ten speed. Plenty of M2's out there but they are too new. I am finding more IH crews in my price range, mostly with the DT 466 backed by an auto.
I won't go with anything but an inline six. Any IH diesels to avoid?
Same question about the Allison auto's. I know nothing about them. i would think a five speed would be better than a four though?
None of the DT466's are engines to avoid, however, some year ranges are better than others. First, I would suggest a power rating of 230HP or more.
My favorite years are the '93-'95. They have a P-pump similar to the 5.9L Cummins pump which a 3rd grader can modify for more power. The injectors are a whopping $35 each, so it's cheap to hot rod or maintain. Next favorite for me is '90-'92. I have this model. It doesn't have a P-pump. It has a Robby Bosch punp that is easy to modify for more power, but not to the degree of the P-pump. Pre '90 DT's have the rotary style pump which is better left alone.
The "NGD" (New generation Diesel) are electronic and started ~'95. They are more difficult to modify being electronic. I think that's the year they started with the HEUI injectors, which are also about $300/each. So figure on much greater expense for replacing injectors.
Moving forward, the Dt466 has basically had the same "improvements" that other diesels have undergone (electronic, more complicated, emmissions, etc.) but the basic engine has remained dead-nuts reliable and bulletproof.
As far as the allisons, they have become much better & more reliable over time. If you're looking at DT466/allisons, the earlier models up through about 1990 came with AT545's. Simple 4 speed autos. I would say to avoid them. Dime a dozen to replace, but not enough gears and no lockup gears-maybe 4th gear. Next generation allison was the MT series which had more gears and more lock-up, but no O/D, so almost all of them run 1 to 1 in top gear. So if you buy a 5.38 reared truck, you might be able to hit 55 MPH. You have to know the rear ratio before you buy or road test to determine top speed. The MT series was a big improvement over the AT series. You'll typically see an MT-653 in a '90's DT466 powered IH truck.
After ~'99, they came out with the electronic MD "World" series transmissions. Ford bought hundreds of thousands of these off GM/Detroit/Allison for their "F-Series" trucks for decades. The 1000/2000/2200/2400/3000 are the most popular names for them. These transmissions are the also called MD3060's in a lot of IH trucks. These are the ones you want. They have double OD's in them allowing for greater fuel economy, lower RPM's, higher road speed and most importantly, more lock-up gears. Typically, they'll lock in 2-6. 1st gear will be available for off-road useage. The gear selector will be a touchpad. These transmissions rock. They can also be analyzed/updated through an elecronic "OBD" type diagnostics port and laptop.
If I were buying another IH with a DT series and an Ally, I'd look for one with an "MD" series electronic auto with the features I mentioned. Much nicer to drive/own. The MT's are a step backwards.
I don't know what years you're looking at or what you want to spend. My DT466 is super easy to work on yourself and a real puller when loaded. I had an F-700 with an AT454, and F-800 with a MT653 and currently have a GMC3500 with a Allison 1000 series. I can tell you the 1000 series is more transmission than either the MT653 or the AT454 that i previously owned & serviced.
My current IH has a Spicer 6+1 manual. I only wish it had an Allison automatic.
http://www.allisontransmission.com/product/
