changing 3rd & 4th gear?

redbugs2000 · Post by **redbugs2000** » Tue Jun 29, 2004 10:39 am

how hard is it to change 3rd & 4th gear ratios?do you have to use special tools?Does the whole tranny have to come apart?
this tranny is SSP IRS.

turboblue · Post by **turboblue** » Tue Jun 29, 2004 6:52 pm

1) PIA
2) Yes
3) Yes

That's the short answer, the long one is yes it is somewhat a pain.
It does take a special pinion nut socket and a jig to set the gear stackup.
And the tranny has to come apart. Might consider a Rancho that's already had that stuff done to it.

warrenbaity · Post by **warrenbaity** » Tue Jun 29, 2004 8:09 pm

actually you may or may not need the special pinion nut socket. it depends on what kind of trans you are talking about. some use the special socket and some use four bolts with lock tabs underneath them. i dont know which trans use which type though. i know that all bus boxes use the large nut, and i think that swing axles use the four bolt, and irs ones use both? im not sure

turboblue · Post by **turboblue** » Wed Jun 30, 2004 5:43 am

The SSC IRS as he described would need the pinion nut socket. I think the very first few bus IRS transmissions had some sort of locking bolt/tab arrangement on the pinion bearing too. I'd have to get my Bentley book out to see.

Post by **Marc** » Wed Jun 30, 2004 6:02 am

You'll be doing almost all of the work required for a complete trans rebuild. Close-ratio gears come "bare" (no synchro hubs) as a rule unless you pay big bucks for ones with hubs already pressed/welded on. Gear endplay is set with selective circlips, it's not uncommon for the dimension of aftermarket gears to be far enough off that machining is needed. And any time a `61-up trans is apart the shift forks need to be properly adjusted, which takes a special jig or at least a similar gearcarrier housing which has been carved open. If the shift rails are carefully marked upon disassembly and the forks reinstalled at the exact same location you may be able to get away without the jig, but I don't recommend it if you're changing anything more than synchro rings.

henryhoehandle · Post by **henryhoehandle** » Thu Jul 01, 2004 4:15 pm

Marc wrote:You'll be doing almost all of the work required for a complete trans rebuild. Close-ratio gears come "bare" (no synchro hubs) as a rule unless you pay big bucks for ones with hubs already pressed/welded on. Gear endplay is set with selective circlips, it's not uncommon for the dimension of aftermarket gears to be far enough off that machining is needed. And any time a `61-up trans is apart the shift forks need to be properly adjusted, which takes a special jig or at least a similar gearcarrier housing which has been carved open. If the shift rails are carefully marked upon disassembly and the forks reinstalled at the exact same location you may be able to get away without the jig, but I don't recommend it if you're changing anything more than synchro rings.

Well said Marc. Old cases will work for jigs, and they can be made less cumbersome by cutting the back part off. 3rd and 4th can be set without a jig as long as you make sure the mainshaft bearing is seated all the way into the housing before you set the adjustment, but since you will already have it in the jig anyway, then you might as well adjust it then.