rear axle identity

[Tango]

And (I have to ask)...are you sure the Allison is shifting into 4th? That's a lot of rpm for that speed and big tires unless the rear is super granny.

[DustinJones]

I can shift all 4 gears manually and count them engage. NC limits school busses to 45mph and it is a NC bus ... Even came with North Carolina scholl district stamped tires bias ply...

[Kubla]

According to my sketchy math, you have a rear end ratio somewhere about 6.8 to one. If you found a 4.44 rear end, you would top out at 65 mph

[Jolly Roger]

My nc bus only does 49 on 9r20's with a 6.50 eaton rear.
How lone have you had your bus? Mine came with the full maintenance records and original factory build/spec sheet.
Maybe go to the bus barn and ask them?
Where are you at in NC? I have seen a huge bus barn on I-85/40 around the Greensboro,mebane,Graham area? My 86 has an eaton rear end and at the time I bought mine the old man at the bus barn told me that no matter ford,Chevy,IHC had the same power train. Maybe that helps?
PM me an email address or phone number and I can send you pics of my rear end with data plates if needed.

[DustinJones]

Jolly Roger I bought my bus April fools day this year . From a private sale hear in Binghamton NY . He bought from NC in 97 I believe he said. The rear in this rig is ID taged as A DANA-HAYES rear end that looks like what I know as a Rockwell rear end . The tag offers no gear information as the Axel housing is just that , a housing for the third member gear set . My power plant is a 9.0 International tuned to 180hp and 300 foot pounds tourqe . .....I keep eye balling a Subaru engine for my bus.... Wrx turbo has the same foot pounds of tourqe .. however 300HP......

[DustinJones]

Thanx Kubla .I would be happy with 60 even. I can take it easy however full throttle for 50 is not good .What formula did you use to calculate that?

[Kubla]

probably a 6.50 axle, like the other poster said he had, basically wheel revolutions per mile (499 for yours) times 49 for miles in an hour = 24,451 revolutions per hour.
2800 Times 60 for engine revolutions in an hour (168,000) divided by wheel revolutions in an hour give you about 6.8, then you have to guess slippage on the AT545 which makes it more like a 6.5 rear

[tweasl]

Originally Posted by DustinJones

Jolly Roger I bought my bus April fools day this year . From a private sale hear in Binghamton NY . He bought from NC in 97 I believe he said. The rear in this rig is ID taged as A DANA-HAYES rear end that looks like what I know as a Rockwell rear end . The tag offers no gear information as the Axel housing is just that , a housing for the third member gear set . My power plant is a 9.0 International tuned to 180hp and 300 foot pounds tourqe . .....I keep eye balling a Subaru engine for my bus.... Wrx turbo has the same foot pounds of tourqe .. however 300HP......

Sorry, even if you could put that EJ25 derived subaru engine in your bus...it would not last a week...your bus has a 9.0 diesel in it for a reason...not a passenger car 2.5 l or so...that subaru engine is meant for a 3000 lb vehicle not a 10000 lb bus...it would self destruct.... HP and torque numbers do the reflect the true purpose of an engine only what that engine is capable of u Der it's design intent.

Sent from my SM-G920V using Tapatalk

[Tango]

Gear/tire size/speed calculator...(the one at the bottom of the page will tell the story)...

Engine RPM Calculator

[MrDaveG]

Originally Posted by DustinJones

Nope Kubla that was my post . My tires are upgraded to handle highway speeds. I get 49 mph at 2800 rpm.. No where near reasonable or safe . I have looked all over and still can not seem to find the charts for factoring gear ratio by yoke stamp.. Or anyone who seems to have the setup my rig has that can tell me anything about there gear set ratios.

A Dana is not a Rockwell. FWIW there are at least 3 major manufacturers of rearends, Rockwell (now Meritor), Eaton and Dana (Spicer). Usually there are some numbers stamped in the end of the pinion shaft so you might have to drop the driveline and pull the yoke to get a good look at it. You could bump tire sizes another size or two, but you'd only get 100 rpms or so per tire size (roughly) so changing the differential or drop-in is the way to

Once you determine which make (Dana) and model (RA39) of rearend, be aware that there can be different spline configurations for both the axle shafts and the pinion

Go to someplace like https://www.heavytruckparts.net/search.php and do a search for RA39 and look at some pictures or LKQs website

Looks like it might be a Dana RA39