will I kill my truck or someone else? DT/466 GCVWR?

[Willie B]

"...converter only in 1st and 2nd, and would run in 3C then shift to 3L and then 4L."

short answer, yes. However, the trimmer valves for shift points can be adjusted by trial and error but require removing the oil pan each time you do it so it can be a time-consuming and frustrating job. The best way is to remove the valve body and take it with the little oil-supply tubes to an allison repair shop that has the calibration test bench which they then attach it to and then do all the calibration adjustments. If the engine feels doggy, maybe the shift points are slightly on the low side maybe caused by the valves springs becoming a bit lazy over 40 years. I'm not sure what a shop would charge for a recalibration. Its been 30 years since i had the last one done

There is a limited amount of information still available for this transmission. What I have found suggests torque converter is variable in 1 & 2, 3 & 4 clunk in. I sense no torque converter action in 3&4.

 

[56wrench]

ok, i was wrong. according to my allison manual, originally configured, the MT640/643 as stated previously should have 1-2-3c then 3L and 4L. also depends how the fire dept had it set up. sometimes fire depts do some unorthodox stuff but not likely. on those engines, if i recall the modulator is a mechanical linkage/cable that needs to be set correctly or the shift points could be affected. i have some information on the old 1980 style brigadier modulator adjustment but not any others. also, the trans governor has to be the correct one as that also affects shift points. if your 3208 is at 250hp, it should be reasonably powered. one place i worked at we had 2 GM tandems with slide-in box sanders and plows on the front and the 3208 power at 250 was adequate for our application. we had some additional shift calibration done but it may have only been 3rd gear hold but i can't remember

 

[Willie B]

ok, i was wrong. according to my allison manual, originally configured, the MT640/643 as stated previously should have 1-2-3c then 3L and 4L. also depends how the fire dept had it set up. sometimes fire depts do some unorthodox stuff but not likely. on those engines, if i recall the modulator is a mechanical linkage/cable that needs to be set correctly or the shift points could be affected. i have some information on the old 1980 style brigadier modulator adjustment but not any others. also, the trans governor has to be the correct one as that also affects shift points. if your 3208 is at 250hp, it should be reasonably powered. one place i worked at we had 2 GM tandems with slide-in box sanders and plows on the front and the 3208 power at 250 was adequate for our application. we had some additional shift calibration done but it may have only been 3rd gear hold but i can't remember

It is 250 HP. Turbo, but not a lot of boost. It has adequate power 1st & second. No powerhouse, but it'll climb any hill as long as I'm not in a hurry. I feel that 3rd & 4th are not participating with torque converter. Maybe I don't want them to, I don't want to overheat the transmission. If I weren't concerned with transmission heat, it'd be nice to have torque converter.

I sure do miss my old 5 speed Eaton with two speed differential. I'd do a swap if it weren't too complicated.

 

[56wrench]

Sounds like you may be low on power. Have you checked for a restricted muffler? You could remove the muffler and try it without. I don't recall how much boost it should have at full load. Maybe somebody else here does

 

[Keith Merrell]

I have 1990 International 4900 dump truck with DT466, air brakes, double frame, spicer 5speed with 2 speed rear, 22k rears, 11k fronts, GWVR 33k. My tag trailer is 20 ton with unladen weight of 9,700 lbs. The million dollar question is what is the heaviest machine I can put on the trailer and not hurt my truck or put myself or other people on the road in a unsafe situation? I have my CDL-A so its not a legality thing just a saftey thing. well and I dont want to kill my 31 year old truck. Input would be great!!!!!!

I was in a somewhat similar situation when I started my business last winter. I had a 2001 GMC C6500 dump truck with air brakes 26K GVW. Cat 3126 motor 230HP 6 speed manual. Pulled a 12 ton trailer with electric brakes. I was running a 310J backhoe on it and it did quite well, but I could really feel it wanting to jack knife when I was taking a really sharp turn that was downhill facing out of my driveway at a very slow speed. The truck was equipped with an exhaust brake that was actually very effective. Coming down a 7% grade was a little uncomfortable without a jake, but it was ok just stabbing the brakes.
Heaviest thing I put on there was a Takeuchi TB290, so about 24,000lbs with the trailer. That was the absolute heaviest thing I wanted to put on that rig. When I would go up copper canyon by Camp Verde 7% grade, I just crawled at 30mph with 4 ways. I think the biggest thing is to do a proper pre trip, keep speeds lower, have good tires, keep a very long following distance, remain patient, and expect the 4 wheelers to cut you off and jump out in front of you, and you will get there safely. Also get a dash cam.
I just upgraded to a 1986 FLC120 tandem with a 3406B and 13spd and I'm really looking forward to it. Just bought an air brake tag trailer today for it. Can't wait to give it a try!

 

[suladas]

That setup looked fine, just needed an adjustment on pintle height.

You'll like the 3406B with 13 speed, that's what I run pulling 30 ton on my tag and it pulls great.

 

[Keith Merrell]

Yeah, that was when I first bought the trailer. I had to lower the hitch on that truck. I've since sold it. It never broke down on me. What are you running a 3406b in?

 

[AzIron]

With a 3406 b series you will easily almost double your speed up copper canyon

I would not have had the guts to do cooper canyon or 13 mile rock with out air brakes on the trailer unless you went down those hills under 40 miles an hour witch would be terrifying with people doing 90 around you

 

[DGODGR]

I used to have a 2 axle Chevy Top Kick (yes Chevy, not GMC) with a 16' flat bed dump. Power was a normally aspirated 3208 with a 10 speed behind it. I used to haul my 18k# CAT 416C (including all 5 buckets and the compaction wheel) on a Zieman 2660 trailer (air brakes, aluminum ramps, 10 tn capacity). That thing always let you know where the slightest inclines were! One of the best days ever was when I bought a 3 axle Peterbilt 359 ramp truck. It carried that backhoe like a dream.
The OP hasn't said if his truck is turbo or normally aspirated. I know that most DT466 come with turbo but I'm fairly certain that some did not (same with CAT 3208). Regardless I think that around 10 tons of payload will be best with that pulling rig. Obviously you have plenty of brakes. In my opinion your transmission is less than ideal (always hated the 5spd with 2 spd rears). The 10 speed is similar but you don't have to deal with the annoying 2 spd rears.
I have a couple of suggestions. Unless you are considering upgrading the tow vehicle (the OP's dump truck in this case), you may consider selling the 20 ton trailer and getting a 10 ton. The only reason is that you are paying a bit of a weight penalty for having a trailer stout enough to handle 20 tons vs. a 10 ton trailer. The other thing I would suggest is that you keep that 466 rung out instead of bogging it to much. In other words be sure to down shift it in heavy engine load situations (like grades) to keep the RPMs up. If your bogging it around that generates a lot of heat. This is what can kill a diesel, especially small ones like the 466. I'm not saying the engine can't handle any stress (they are actually pretty tough and resilient). I'm just offering a suggestion to help you get the most life from your application.

 

[Keith Merrell]

With a 3406 b series you will easily almost double your speed up copper canyon

I would not have had the guts to do cooper canyon or 13 mile rock with out air brakes on the trailer unless you went down those hills under 40 miles an hour witch would be terrifying with people doing 90 around you

Yeah, I was going down it in 5th at about 50-60mph, I had to come to an abrupt stop once, and it worked fine because I never let the brakes get too hot. That always made me nervous seeing the dummies running dry vans down there at 85mph whizzing by though...

 

[suladas]

Yeah, that was when I first bought the trailer. I had to lower the hitch on that truck. I've since sold it. It never broke down on me. What are you running a 3406b in?

92 Western Star. It's not a combo i've ever wanted more power with it takes a very steep grade to have to downshift grossing 90,000lbs. I just wish it had another gear because it tops out at 55 mph.