4.56 gears what options do I have

rbrlsn · March 11, 2011, 05:17:07 AM

1986 gillig 4.56 gears not for sure the make but the number that gillig gave me is 59743 and 53-16328-5 do these #'s tell you guys what the make is on this drive axle so I can have some place to start looking for a higher gear ratio to get a little more speed. I want to be able to have one waiting on the ground before we pull the other one out.

buswarrior · March 11, 2011, 05:34:39 AM

4.56 is the gear in lots and lots of new coaches.

An overdrive transmission like a B400 would go nicely with those.

Lots of good transit take outs available.

happy coaching!
buswarrior

TomC · March 11, 2011, 07:52:32 AM

If you have an older Gillig, you probably have the direct high gear HT740 Allison in it. So with 4.56 rears and 485rpm 12R-22.5's, you're top speed will be a little over 62mph at 2300rpm. One of two ways to go-the best would be to just change out the transmission to the Allison HD4060/B500 transmission. The first four gears are just about exactly the same as the HT740, but with a .74 and .64 over drive. So with your gearing, you'd have a top speed of 84mph in 5th and 97mph in 6th. Or more realistically, you'd have an engine speed of 1772 in 5th and 1533 in 6th @ 65mph, and at 75mph you'd have 2045rpm in 5th and 1769rpm in 6th-geared perfectly for the World transmission. This also has the advantage of maintaining the same startability as you have right now since the first four gears are the same.

The other way is to change the rear end ratio. To get a good comfortable cruise at 75mph at 1800rpm, you'd have to change to a 2.95 rear end ratio-which they make. Or more commonly a 3.08-which would give you 1618rpm @ 65mph and 1867rpm @ 75mph. Changing the rear end maybe simpler, but then your startability will be noticably more lethargic. Depending on your engine, you may risk getting stuck on a steep road.

Let us know what engine you have. Good Luck, TomC

rbrlsn · March 11, 2011, 02:26:39 PM

I have a 6V92TA 253hp w/HT748 trans

luvrbus · March 11, 2011, 02:50:03 PM

You are already electronic go with the B400 double overdrive it is going to be about the same price as changing the rear gears plus some Eagle guy installing a ISM will buy the 748 they are short in length allowing for a tee drive in a Eagle doing away with Eagle drop box

good luck

Tim Strommen · March 11, 2011, 04:29:11 PM

I second that - B400/500 or a take-out HD4560 with first gear start. Awesome setup, lots of control.

-Tim

rbrlsn · March 18, 2011, 11:39:07 AM

well just found out by my mechanic the engine problem is deeper than we thought so a hold on everything till we get this figured out. Went in as injector issue, well i'll update as I find out something

RoyJ · March 18, 2011, 11:40:29 PM

Perfect. Do an ISL + B400 swap

Just kidding, hope nothing too serious.

TomC · March 19, 2011, 08:51:13 AM

With my AMGeneral 10240B transit, the Canadian version was called a B800 and unlike my V drive was a straight drive. If my engine ever goes out, I would change it over to a straight drive using the Cummins ISL at 450hp and 1250lb/ft torque. With changing the 8V-71 and V730 to the Cummins ISL and Allison 3000 (B400), the engine/transmission would be about 1,000lbs lighter. In my truck, I would use the same setup if California ever requires single use RV's to come up to smog standards. Good Luck, TomC