Low Gear Conversion

[morriskelly]

Hi,

I have a 1999 international 3400 t444e 7.3 powerstroke turbo diesel, it was used as a local shuttle bus. I have converted it into a party/ limo bus inside, but can only do 55 on the hiway to get to the casinos. I heard there is a way to upgrade the gearing, as well as using bigger wheels to fix this issue. Please help!!!!

Thanks
Will

[kotflb]

There are several things you can do. Changing tire size will net you from 3 to 5 mph. Changing to an overdrive transmission will net you 10 to 15 mph, tho changing the rear axle ratio may be cheaper and you can probably go to 85 mph or until you run out of horsepower. Some may suggest that you just turn up the injector pump to get more rpm out of your engine, but if you go that route, it may or may not cost you a mpg penalty. Other more knowledgeable members may know for sure.

[morriskelly]

Thank You @ kotflb!
That helped a lot! by any chance would you have any more info on the gear ratio that i have and maybe what i should change it to? and or how to turn up the injector pump? Again Thanks a million!!

[morriskelly]

Thank You Very Much!!!

[kotflb]

Thank You @ kotflb!
That helped a lot! by any chance would you have any more info on the gear ratio that i have and maybe what i should change it to? and or how to turn up the injector pump? Again Thanks a million!!

To determine your present axle ratio, I need to know your rear axle tire size, and what rpm your engine is turning at what mph. To determine what your bus CAN do with gear changes, I need to know what horsepower your engine is making (should be a decal on the valve cover). And what model # transmission ( should be a plate on the side of the transmission, AT545 etc) you have.

Nevrenufhp has some good info on turning up the pump here: viewtopic.php?f=44&t=588&start=30 Read the whole thread and follow his links.

Just for a wild guess, it seems you may have a 190 hp engine, connected to an Allison At 545 trans, with a rear axle ratio of 5.38 or higher.

[Stuff]

get the rear end ratio checked out and see if you can get a more highway friendly one put in.

[morriskelly]

You guys are F*ing awesome!!!! I checked the tag on the engine as you stated it says 190 hp @ 2300 rpm. I couldn't find the tranny tag as it is 1 something in the morning and about 6 degrees outside. The rear wheel size is 245/70/19.5 You guys are making me sleep very well with a glimpse of hope...thanks for the early christmas present!!

[kotflb]

Thanks for the flowers and sorry for the delay in getting back with you.

You may be in luck here, seeing that you've got 19.5 tires on your bus.
It may take a bit of searching, but I believe you can just go to a larger tire and rim. I suggest a 22.5 rim with tubeless tires. You stated in your first post that you can only run 55. If you are turning 2300 rpm at 55mph, that equates to 4.11 rear axle ratio, which is good if you can locate the rims and tires to bolt up to your existing hubs. With 295-75/22.5 tires, you can run at 66mph at 2300 rpm. With 1100/22.5 tires, you can run 69mph at that same rpm. But!!!!! (there's always a but somewhere) with your horsepower you will be limited to a flat road, no wind max of about 68 or 69mph. Add a bit of wind or a slight incline and your down to the low 60+ mph. And that is when it's time to start tweaking the injection pump. A good tune on the pump could have you cruising like a Greyhound bus.

I hope this helps in some way, if you need more specifics, let me know, If I don't know it, I do know where to find it. Merry Christmas

[morriskelly]

Hey kotflb, Thanks again! I followed the link on increasing the fuel rate, the only problem is that all i found was twaeks on the dt446 engine, not to mention hearing that the t444e engine that i have is considered the yugo of diesels. I heard of the possible power tweaks for the dt446, is that an easy swap in my chassis?. or are there any direct links for tweaking the t444e engine.

Thanks again!

[kotflb]

[quote="morriskelly"]Hey kotflb, Thanks again! I followed the link on increasing the fuel rate, the only problem is that all i found was twaeks on the dt446 engine, not to mention hearing that the t444e engine that i have is considered the yugo of diesels. I heard of the possible power tweaks for the dt446, is that an easy swap in my chassis?. or are there any direct links for tweaking the t444e engine.

Start Here for your engine:
http://www.freewebs.com/nevrenufhp/index.htm Look down about halfway the page.