Road Ranger Gearbox

Hi Everyone, I'm currently working on a 1973 K125 COE with a V903 and a 15 Speed RR. The Diff ratios are 5.29 so its a little revy at higher speeds. Doing some research I noted that in the later K104-108 there is a double overdrive box RTL014713B. Does anyone know if the outer RR casing is the same, My thoughts were to have the internals replaced with this gearing as the 15 speed needs some work.. It loves to jump out of gear when your not suspecting it. I had a quote to get a 2nd hand one over in in Wait Awile and it was 6K..is that a fair price??

Hi, if you give Soltogios a ring they have a few rtlo2018b gearbox,s there, I would expect to pay 5 or 6k for one of these, not a 13speed an with 2000lbs of torque you wont break it in a hurry. more gears are better than less to, so if you get stuck any where pulling what ever you get into with it.

Grant

903's like to rev, 5.29's with a direct box should give you about 60 mph. An overdrive 13 or 15 speed will probobly give you another 10 mph. You only need a 9 series box for a 903, should be between $1,500 and $2,500, as in a RT9515 or overdrive will be RTO9515, if it's RTF or RTOF it just means the gear lever position is forward.

Thanks Ducky - Big cam, Sounds like the best way to go is to overhaul the box I have in her at the moment RTO9515. I have had a look inside and its been worked on, I recon I would need some new selector forks, these are worn and the clutch dogs look a little worn but all else looks ok. She is a sort of long term project, I believe has potential as she is in good nick.

This site is fantastic, I have been searching the internet over the past 2 years and found information is difficult to get for cummins motors. It sounds like many of you on here have had a fair bit to do with them. I havenet driven for a few years now but still have the passion, When I did drive I drove a couple of 555's in acco's and a 903 in a loosly built, Then went Euro with a Scania. The thing i liked about the 903 is its so simple for the power.

Anyhow, thanks again
Cheers Kenny

Selector forks won't be the cause of it jumping out of gear. If you look at the dog on the gear it jumps out of you will find it worn. That isn't to say the selector forks arn't buggered as well.

Hi, and have those counter shafts an gears checked, as I think some of the gears should be pressed on them and if not then theres more bucks. it wont be your jumping problem but still a problem. my 20speed will be due for a build in next 12mths and it has a loose 3rd on the countershafts, 10,000 to rebuild it.

Grant

Thanks Grant, Its going to be a while before I get to it but its good to get some feedback on different things that happen to them.

Regards
Larry

My old 1980 K125CR has a direct drive RT915 10 speed with 4.1's and seem to match up well.

Agree with the others regarding jumping out of gear, the dog clutches on the gears would most likely be the culprit, I'd check the selector forks for wear and straightness also, some cowboys love to swing on the gear levers .

It's a big job, but maybe changing diffs further down the road could be an option, but to get things sorted I think a rebuild on the current box is a good idea also.


A

Thanks A, I might look at the Diffs also, I noticed the front diff has a leak in the drive seperator. Looking around these are better priced too.

Laz.

give Gavin a call at beenleigh truck wreckers at yattala south of brizzy , he told me a couple of days ago, he had stacks of b-double rated 18 speeds,starting around 4 geeeee,s old school truckers call em double over drives , with this type of box you will have good legs ,and still be able to hook up and pull a trailer..might save changing the diffs