changing gears from 2.56 to 3.55 i bought a spacer that is .230 thick should i use another .100 spacer to get it close to right carrrier size?
i have the 1 .240 spacer in now and looks like i can shim carrier over to get correct back lash by adding extra .100 shim to carrier bearing on drivers side and taking away .100 from pass side .i just dont this to be issue later the only issue i can see is that axle engament may be less on driver side
please advise if i need to change my plan
bop 8.2 gear swap
Re: bop 8.2 gear swap
Spacers in a BOP 8.2 rear are tricky.
The stock posi units are a 2 piece set-up meaning the cone is one piece and the side gear sits on top.
So if you do not have it centered enough in the case you could risk engaging only one piece and it will ruin the unit very quickly.
so a 2 series flange is about 1 5/8" (1.625 )compared to the 4 series which is 1 15/16" ( 1.938" ) a difference of about .313 So you will need as much as you can.
BUT you also need to watch how much inner ring gear body machine land you have left to keep the ring gear centered. IF you come up above the machined ring gear centering surface the ring gear will be relying on ring gear bolts alone and WILL FAIL.
So be careful BOP carriers have 3 breaks in the 64-67 era and 4 carrier breaks in the 68-70 era.
I would do only the .240 as it is much more important to keep the ring gear on the machined surface hub of the carrier or failure will occur for sure on the ring and pinion.
axle shaft engagement. : after you get the carrier in and where you think it is correct. Double check the axle shaft and how much is in the side gear.
IF you have a super duty unit...You will not be able to see how much each axle engages the side gear. It should be only .050 to .060 off and the side gear should be .500 thick leaving you with .450 to .440 ish to engage.
BUT again we do not know how off center the ring and pinion mesh to be correct will take the carrier either.
Like i said .... it is touchy
Jim
JD Race
The stock posi units are a 2 piece set-up meaning the cone is one piece and the side gear sits on top.
So if you do not have it centered enough in the case you could risk engaging only one piece and it will ruin the unit very quickly.
so a 2 series flange is about 1 5/8" (1.625 )compared to the 4 series which is 1 15/16" ( 1.938" ) a difference of about .313 So you will need as much as you can.
BUT you also need to watch how much inner ring gear body machine land you have left to keep the ring gear centered. IF you come up above the machined ring gear centering surface the ring gear will be relying on ring gear bolts alone and WILL FAIL.
So be careful BOP carriers have 3 breaks in the 64-67 era and 4 carrier breaks in the 68-70 era.
I would do only the .240 as it is much more important to keep the ring gear on the machined surface hub of the carrier or failure will occur for sure on the ring and pinion.
axle shaft engagement. : after you get the carrier in and where you think it is correct. Double check the axle shaft and how much is in the side gear.
IF you have a super duty unit...You will not be able to see how much each axle engages the side gear. It should be only .050 to .060 off and the side gear should be .500 thick leaving you with .450 to .440 ish to engage.
BUT again we do not know how off center the ring and pinion mesh to be correct will take the carrier either.
Like i said .... it is touchy
Jim
JD Race
J D Race
Re: bop 8.2 gear swap
ok thanks for info im test fitting with the one .240 spacer and looks like adding extra .075 worth of shims on ring gears side bearing gets me real close on back lash .008 to .010 depending on gear i check on and smallest shim i have is .005 if i add this i get 0 backlash so it looks like i will have to live with the .008 to .010.im going to mess with it again tonight after work and see if i can get it any better and see how pinion looks after few swipes thru paint .any good tricks to getting pinion bearing back off without damaging it ? stock shim was .036 and i went back with that and it looks like it may be little close to ring but i dont want to screw it up by taking it back off
Re: bop 8.2 gear swap
.008 to .010 is perfect for GM used gears.
So what is the driverside shim what is the passenger shim thickness?
So what is the driverside shim what is the passenger shim thickness?
J D Race
Re: bop 8.2 gear swap
Send pics of pattern before removing anything.
You will need a larger splitter type bearing remover and a press is the best.
I really do not like the heat thing as people usually get the bearing too hot and end over over tempering it... they it will fail.
It is something you might do for a demo derby car or farm truck but try to use the proper tools
You will need a larger splitter type bearing remover and a press is the best.
I really do not like the heat thing as people usually get the bearing too hot and end over over tempering it... they it will fail.
It is something you might do for a demo derby car or farm truck but try to use the proper tools
J D Race
Re: bop 8.2 gear swap
as of now driver shim stack is .315 pass side is .166 with stock 256 gear set it had .240 on driver and .241 on pass side
this is 1968 firebird rear end with open carrier
this is 1968 firebird rear end with open carrier