7 Window DT466/MD3060 Gearing Question

[PorchDog]

My 7 window 1995 Bus has a mechanical DT466 rated at 210 HP with an Allison MD3060 and 6th gear is NOT unlocked.

It currently has 10R tires, but I think I will change to 11R some day. It came from the factory with a 6.14 rear axle ratio.

My plan is to live without 6th gear-- but change the rear axle ratio.

Per the Spicer gear calculator--- using 41.75 inch diameter tires--and going to a 5.38 rear axle (which is a pretty big change) I get--

4th gear (1.00) 2350 RPM equates to 54.28 MPH

5th gear (0.75) 2000 RPM equates to 61.59 MPH.

60 to 65 MPH is about my normal speed. Mostly 62 or so.

Will I be happy with the 5.38? My only other choice would be 5.63. This is a pretty pricey undertaking-- so trying not to screw it up.

??????????

 

[magnakansas]

iffin my math is correct

65 mph going to be around 2250 rpm with converter locked.
70 mph about 2400 converter locked.

seems reasonable to me. gonna downshift to fourth gear if you cant make enough torque.

that's the way I see it.

william

 

[Omnibot2000]

At first glance your numbers look right.

I run a 5.63 Ratio and I am content with it. I considered a 5.38 like you but availability and price became a concern. Reality is could not find a 5.38 in Canada.

I have a full length bus and replacing tires to 11R22.5. I measured the rolling distance from new 11 tire to worn 10 tire and gained additional 6 inch rolling distance. I will recheck again today but that was a little over 4%. That's 1 step gear drop territory. Generally it's 2-3% Could be more for me as my 10r tires only have 30% tread remaining.

You engine also has more lower end torque then my T444e. 5.38 ratio will be fine. Especially with only being a 7 window. That bus of yours is a rocket off the line with that powertrain set up being only a 7 window.

 

[PorchDog]

Thanks very much for the replies.

I am going to begin the search for a 5.38. It just helps to run these things by some more folks to validate my thinking.

A couple of years ago--- LKQ had good prices on a reman unit-- whatever reman means-- they gave you a six month warranty, shipped out of a town south of Chicago.

The bus came out of California-- Los Angeles Unified School District-- apparently they had money back in 1995-- it has a higher ceiling height, tinted glass, AC, air ride rear suspension, and a MD3060. BUT-- it has over 300,000 on the chassis. I do believe the engine has been redone-- the front timing cover is painted a different color blue, and when I sent an oil sample off-- it came back very clean. The transmission appears to operate fine.

Some folks own a boat, or a lake house, or an airplane-- I get my kicks out of spending money on school buses. I don't keep up with what I spend, just chalk it up to entertainment, and that also gives me plausible deniability with the wife.


:Thanx:

 

[cadillackid]

I'd go with the 5.38 and unlock the 6th if anyone will do it on the WTEC-II. you can also safely turn the screws on that pump up a bit to get yourself closer to that 250 mark on an NGD-466 and go with a 5.13 in a short bus..

 

[cadillackid]

Thanks very much for the replies.

I am going to begin the search for a 5.38. It just helps to run these things by some more folks to validate my thinking.

A couple of years ago--- LKQ had good prices on a reman unit-- whatever reman means-- they gave you a six month warranty, shipped out of a town south of Chicago.

:Thanx:

thing to remember about LKQ and a few years ago.. so many of these parts if a SKU is no longer used by IH in the factory, by law they must maintain that SKU for purchase up to 15 years... after thats up, if they dont have high sales of a part they may choose to take it off the list of available parts and LKQ seems to be right there to grab em up.. around 2018 / 2019 IH Ditched a Huge number of driveline and transmission parts.. I suspect it was related to the fact the Body style of their trucks and bus chassis had changed from 03 to 04... there were boatloads of transmissions, engines, axles, rear end chunks, etc for Cheap.. (its where i got a reman still dry MT643 for $600)...

 

[PorchDog]

I'd go with the 5.38 and unlock the 6th if anyone will do it on the WTEC-II. you can also safely turn the screws on that pump up a bit to get yourself closer to that 250 mark on an NGD-466 and go with a 5.13 in a short bus..

Unlocking a WTEC-II is a problem, and expensive from what I can see. All the usual folks that do the III's say they can't do a II, and you have to ship off your known good II, and if it got lost, or someone messed up the programming-- you are in a huge mess.

That's why I made the decision to live with it -- at least for the foreseeable future.

And I remember back when LKQ had those basically new or reman transmissions for dirt cheap. Maybe that is where these rear differentials are being sourced? IF they still have any...

Thanks for your input!

 

[sportyrick]

Mine is Dt466, 3060 with 6th unlocked, 4.33 rear gear, 42" tires, 1550@ 70 MPH, I would think about even lower than 5:35 w/o a 6th gear, like high 4's in my mind. Call ECM King and ask about unlocking 6th gear.