Gear swap??

[RAD1229]

  My 72 challenger currently has 2.92 gears, good gears but I am looking for a little more jump.  Have a new 3rd member from 68 dodge truck also 8 3/4 with 3.55.  I thnk that I will like this ratio, but I am curious as to what I am getting into by swaping the 3rd member out?

Is it simple?  Ami going to have to pull the axels? Is this a common procedure?  Just looking for some pointers, don't want to get in a jam!

Thanks for any help!

[Robb_Scottsdale]

Im going to be doing something similar here PDQ, same gears.  So ive been reading and shopping a little.  I was just going to ask this topic myself !  You have great timing !


all the manuals and instructions Ive read talk about reoving the Axles completely, and thenhaving to use special tools to put in new seals and bearings and setting some kind of adjuster for end play (IIRC)

but Im wondering if a guy just cant slide the axles out 10 inches or so, far enouhg to allow the old pumpkin to come out, and the new one to go in, without having to do all that other stuff each time.    I dont know...   hope someone here does.


You will want to check the yoke on your new pumpkin, if its not the same, then you either have to install the right yoke OR you can buy a special U-joint that will adapt a small yoke to a large yoke mate-up.


Wen you do this, post how things go for you !

[Chryco Psycho]

there are 34 bolts to remove , 4 for the driveshaft , 10 for the wheels , 10 for the axles , & 10 for the pumpkin , you have to pulll the axles out at least 8 " but that is as far as needed , the3 center section is heavy , it is best to use a jack to remove & install the center , I just use a bead of silicone to seal the center up , no gasket , After reinstalling the axles you Have to reset the end play, there is a threaded ajuster on one axle that can be screwed in & out of the retaining plate , you need to set the end play at approx .010 and us a hammer to drive the axle all the way in & seat the far brg , if you have to much or too little play you will hurt the brg , Also repack the brgs with grease while they are out as they do not oil from the diff oil , you don`t nessisarily need to replace the brgs but they should be replaced if damaged  

[mustardketchup]

Thanks Chryco:

     You gave me the step-by-step for a project I was going to tackle this weekend.  Bye the way, I think I need to shave down the cone by about 0.080" in my '489 rear.  When it was last under 383 power, only one wheel was spinning (and yes, it is definitely a Sure-Grip, not an "open" rear).  I believe Mopar Muscle touched upon this rejuvenation project (shaving the cone to get both wheels griping again) with success, but Ehrenberg from Mopar Action says that trying to do this on the cone-and-clutch '489 Sure-Grip is a no-no. Has anybody done this Sure-Grip rebuild with any success?  I'd hate to lay $300-$400 for a new Sure-Grip when I can simply shave down the cone on a lathe and bring the rear back to life.  

      And by the way, the people on this site do have great timing for asking the questions that were on my mind (to quote Robb Scottsdale).

Larry

[RAD1229]

Just Wanted to Thank Robb and Chryco for the info.  My 2.92's are great from about 30--> but I am looking for a bit more jump.  Thanks to you guys On Mon. or Tues. I will find out.  My car is mainly a cruiser but you can't build up a mopar with out power
Besides its been a  Blast.  

I wish I could have started with a more complete car but I wouldn't change anything if I could.  One day hoping to slap a big block in her but thats down the road, heck amybe in my next Mopar!!

Thanks again Guys!

[Chryco Psycho]

i have cut the end of the cones down , it does work , not nessisarily the right way but it will save  a few hundred $$ & the one you have is basically junk anyway  

[mustardketchup]

Thanks Chryco:

    Then I guess I'll be doing the same to my '489.  Thank you for the help.

Larry

 

[RAD1229]

   Chryco,

  Thanks for the info on the exchange.  I am almost back together, but i ran into a problem.  i am sure its nothing too big, but I don't want anything go back wrong.   The swap went over without a hitch, the drivers side axel bolted back up no problem, but ont he passenger side when I bot the axel up it doesn't snug up to the brake unit.  The entire backing that holds the braking mechanisms still has slack in it.  I know it wasn't this way when i disassembled, and i want to make sure it goes back correct.  Dou yuo know if there is anything that I can do?  It's almost like the axele needs to go in another 1/4 inch, but its already very snug?  Any ideas??

-Thanks,
RAD

[Robb_Scottsdale]

, After reinstalling the axles you Have to reset the end play, there is a threaded ajuster on one axle that can be screwed in & out of the retaining plate , you need to set the end play at approx .010 and use a hammer to drive the axle all the way in & seat the far brg

Rad,
Did you do that part of the operation  ?  

[RAD1229]

I've played with the adjustment in bith directions and can't seem to gain any ground,  it eventually gets too tight in both directions.

  Should this be done before or after securing the axel bolts?

-RAD

[Chryco Psycho]

if it has a sure grip you may need to rotate the axle to line up the clutches as you slide it back in , you usually need to use a crowbar between the studs to turn the axle , it is just the splines that are not lining up

[RAD1229]

Thanks guys, I am in the process of trying to correct everything.   I figured that that was the prob, but it felt like it was aligned??  Gonna try again, thanks again!

-RAD

[RAD1229]

Aha, turs out all the trouble over a not so cooperative bearing race!  got the thing back together and on the road.  I really couldn't tell a whole heck of a lot of difference.  Turns out my old gears were 2.76 (not 2.92)  I really think that because this isn't really a race car, and its not built for torque that i am gonna go back to my 2.76 ratio. I think that it will be less strain on my motor over time, and I really love the way I can get on it when i'm creepin at 65 and it kicks down and lets me string out second.  You can't beat passing somebody like that.    Oh well, thanks for the info and help, if you want to voice your opinion on the gears I'd love to hear it!  

[Chryco Psycho]

go for it , whatever makes you happy
 

[Robb_Scottsdale]

Did you retune your car (any carb adj and/or distributor timing) for the new gear ratio ?


Not much of a difference ?   shucks.  

Ive been all jazzed about getting my done as when I was younger had some friends that had dads building cars with them, and I remember gear swaps as being some of the most "bang for buck" difference.