International MDT questions.

jovibuilt

Well-Known Member
Joined
Dec 1, 2006
Location
spruce pine nc
Anyone know a good forum for International MDT? I bought a toy hauler 1989 international s1600. Has 189,000 miles.Has the na 7.3. It has a governor on it max speed of 65. I just want to be able to run 70-75 on the interstate. And do a few upgrades to help mpg. I will never haul more than 2500 pounds. I know the na 7.3 is weak but surely I can get it to run on the interstate at speed and get 15-20 mpg? Anyway I am looking for a forum oilburners is dead so I am looking for a better forum. Thanks
 
jovibuilt said:
Anyone know a good forum for International MDT? I bought a toy hauler 1989 international s1600. Has 189,000 miles.Has the na 7.3. It has a governor on it max speed of 65. I just want to be able to run 70-75 on the interstate. And do a few upgrades to help mpg. I will never haul more than 2500 pounds. I know the na 7.3 is weak but surely I can get it to run on the interstate at speed and get 15-20 mpg? Anyway I am looking for a forum oilburners is dead so I am looking for a better forum. Thanks
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Never going to happen. 20 mpg in a modern, more aero 1 ton truck is only possible if you go off the digital mpg gauge. My 06 3500 2wd ram avg about 28mpg. Or hand calculated avg 17mpg empty
 
Do you want it to run forever or run fast.
Pick 1.

I’d either leave 10 minutes earlier or add a turbo...
 
I've driven quite a few MDT and maintain our fleet
They are usually underpowered and over geared. Both of these allow them to last a long, long time
I took off the electronic governor on our 2006 FTL M3 with a C7. It was limited to 62 electronically. A trip to the dealer took care of it for me.
In your case it's likely the rear gear keeping it limited.
 
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Even if you uncork it, you’ll probably be limited by gearing. They’re usually spinning a pretty good bit even by 60. I had the same idea with the Cat3116/5spd Kodiaks at the in-laws til I looked at what they were turning at 60mph. Most trucks in that category can get about anything moving from a stop but run out of steam quick.
 
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jovibuilt said:
I want forever but still need to be able to get out of everyone's way lol. Turbo from what I have read only adds 80 hp.
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Only 80? that’s probably a 50% increase.

But as said before, you are probably running out of gear/RPM, not power.
 
The "governor" on an IDI is internal in the injection pump. Off memory it's set de-fuel at a certain RPM. It is somewhat adjustable, but the only thing you'll gain is the speed difference from the 1k(ish) extra RPM. I'd say most likely you're running out of gear. You'll be lucky to see 8-10mpg out of that vintage MDT. What trans is in the truck?
 
Spicer 5 speed with the low first gear. So really a 4 speed. I need to crawl under it and see the rear ratio. I am almost positive it is a spicer rear too.
 
I had a 6.9 IDI F350 for a while. I can't imagine how slow a medium duty truck is with an IDI motor. Top speed was 67mph, downhill with a tailwind. But it was much happier at 55-60mph. I believe it was geared 4.10.
 
Hadn't been mentioned, but if running out of gear is the issue, with the lesser load(2500#) would either re-gearing ot putting a different rearend under it not make sense to get the speed you desire? I am thinking it would also help with the MPG's, running less RPM's.
At least that's what I am thinking.

There have been times when I was towing, a few different rigs, I would have been very happy being able to do 65. So I did as what was mentioned. I started sooner, held the right lane, and just went.
 
Here is couple of phone numbers to a couple big truck junk yards in Bristol, tn. Kings heavy duty truck parts 423-538-0921 or 423-383-1308 Bays truck parts 423-279-0404 They both are good people to deal with.
 
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Link to the listing
SPICER ESO66-7B Transmission Assemblies For Sale Charlotte NC LKQ Heavy Truck - Charlotte - 7221689
 
LT1JEEP said:
Here is couple of phone numbers to a couple big truck junk yards in Bristol, tn. Kings heavy duty truck parts 423-538-0921 or 423-383-1308 Bays truck parts 423-279-0404 They both are good people to deal with.
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YotaOnRocks said:
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Link to the listing
SPICER ESO66-7B Transmission Assemblies For Sale Charlotte NC LKQ Heavy Truck - Charlotte - 7221689
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Thanks so much! Going to call Kings and Bays today. And see prices if their more I will buy the LKQ one. Thanks again guys.
 
I've driven over a 100 various large trucks. Even an 89 F450, 7.3, 5 sp.. Seems the rear was 5.13, because it didn't have a Real granny gear. 70mph was pretty much it. A former oil truck, converted to dump truck, with a 10 sp, was governed at 65. Shop deleted the governor, & it hit 90! Dump trucks I'm in now, Cat C7, with either 8LL or Allision 5 sp., run around 70-75. Don't know the rear gear. Some of the Roll back guys, run the Small engine, & 5-6 sp, with some doing 90mph! Mostly the rear gear, but if you want to cut down on RPM, you get an Overdrive, or double OD.
 
LT1JEEP said:
Here is couple of phone numbers to a couple big truck junk yards in Bristol, tn. Kings heavy duty truck parts 423-538-0921 or 423-383-1308 Bays truck parts 423-279-0404 They both are good people to deal with.
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Kings doesn't have one if he did $950. Wish he did.
Bays doesn't have one if he did $1700. With a core. And I don't have a core.
And the LKQ one needs rebuilt good for core only. They have rebuilt ones for $3500 not counting core charge!WOW
So still looking. Probably need to buy the LKQ core and try rebuilding it myself?
 
You can try marsh truck parts out of siler city. They have an auto yard and heavy duty truck yard.

Dave

Sent from my SM-G973U using Tapatalk
 
The 6+1 transmission there is 2 different transmissions like this one is for hydraulic brakes and the other is for airbrakes. My truck has juice brakes and the imput shaft is smaller and it has a ebrake on the back of the trans, The air brake trans has a bigger imput shaft and doest have the ebrake on the rear and the yolk is for a bigger ujoint too. That is how my truck is set up you can change the parts out to make the other one work. I have a couple of them for parts I have robbed them a few times. My truck is a 4700 the transmissons I have bought was out of a 4900 and had to change the parts around.
 
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