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Topic: 2- Speed final drive (Read 1049 times) previous topic - next topic

2- Speed final drive

Just about finished putting a 2-speed final drive in my 80 Foretravel FTX pusher. I would say I switched rear ends but the rear end of my coach is the motor. :))

The job was about as entertaining as one might expect. I went from a 5.29 final drive to a 4.88/6.64 which will give me about 4 more MPH (previous top speed about 60 @ 3000 rpm). The low range should give me some splits in 2 and 3, and a pretty good under drive in 4 when I need it. (I have the Allison MT640 trans and Cummins VT555)

I did this same upgrade to my septic pumper last year (CAT 3126, Allison 3060) and was quite happy with the results.

We are getting pretty close to our first trip. (Already did the shakedown when I drove 619 miles from San Diego) 
1980 FTX 38 RED

Re: 2- Speed final drive

Reply #1 –
Interesting upgrade.  And I have often wondered why motorhomes don't come with a 2 speed rearend.  Except for the possibility for a owner messing up when splitting the shift.  That "clunk" would scare the heck out of a lot of folks.  Can hear them now  -  "Did I break it??"
1994 U225
build #4514

Re: 2- Speed final drive

Reply #2 –
I can imagine ripping the tail shaft housing right out of that Allison with a seriously bad shift technique, so I probably won't let my grandson drive it!
1980 FTX 38 RED

Re: 2- Speed final drive

Reply #3 –
Rick,

Nice work. Sure would be nice to reduce highway rpm by 10-15%. Probably hard to find a low mileage rear end assembly. How much used? Can't remember what mine looks like but is this just replacing the third member with a two speed or (raining outside or I would go take a look)? Driveshaft mods? Probably would make the 3rd to 4th shift at 55 mph instead of 48 mph. Multi speed manual transmission would have made this unnecessary.

Pierce & Gaylie
'93 U300/36

Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: 2- Speed final drive

Reply #4 –
Well I was lucky to have an Eaton final housing cause I wouldn't have even tried it if I had had to change the housing. (heavy welding for the air suspension radius system)

Eaton used the same housings for single speed and two speed finals in that series (17220)

I did have to shorten the drive spline a bit because I forgot to check the yoke length on the new drop-in and had to lose 3/4 inch or have no slip left, and there wasn't quite enough room to get the one inch drive impact in there to change the yoke after the install.

I'll report on how it works out
1980 FTX 38 RED

Re: 2- Speed final drive

Reply #5 –
It works!
1980 FTX 38 RED