www.jdrace.com

I have a Type O , 31 spline, carrier casting 672 from my 1967 442 currently with 3.42 gears.
My first and main question is trying to find out if there are any R&P sets available for this unit in the range of 3.90 - 4.33?

In reading the sites info and stuff for sale, it appears as though there isnt any gearsets of these ratios available for my housing?

If this is correct, then I must look for another housing because i want to have a ratio somewhere btween 3.90-4.33.

I do also own a Type P 3.08 Posi rear (2 converging webs in centersection) housing from another 67 cutlass that i bought as a parts car. Its laying in back of shop with thought of using if i wanted to switch to my car to a "road" gear.

It appears from reading on your site that there IS the lower gears available for this type P, but that the type P is a much weaker rear than the "O"??

I am going to use this rear in my restored 67 W30 car that will be a street/strip W-machine with modified 400 +.060 Big Block Olds with a lot of torque that should do 1/4 mile in low 12's (TH 400 w/ 3500 stall).

What do you suggest if I cant get gears for my type "O"?? Back "in the day" when i raced the car (67-70) i put a 12 bolt type C Chevelle housing under it with 4.56. I was told at the time that i would "shell" the stock W30 Type P with the cone-type posi because it wasnt nearly as strong as the 12-bold chevy. The 12-bolt chevy never lost a gearset in it the entire time i raced it!!

Thanks for listening and giving me some advise.

"o" type rear- this is a hard rear to restore these days...reasonably priced anyway...

The aftermarket gears made by Richmond Gears are for the 3 series open or posi (671) carrier - They carrier 3.42 3.90 and sometimes you can get 4.10.

Strength- Well all rear work well when they are maintained and up to spec. Most people use a rear till it blows and then blame the size for the failure when in fact it was just old and sloppy. The olds 'O' 12 bolt does have a slightly larger ring gear than the comparable 8.2 10 bolt Chevy or Pontiac and Buick rears. The down fall with most of the 8.2 and even the olds 12 bolt is the pinion shaft taper at the yoke. ALL 10 bolt 8.2 BOP (Buick OLDS Pontiac are 27 spline and use a small outer bearing) even the 12 bolt 'O' type rear does the same taper to a 27 spline yoke and smaller bearing again. They all use the same part bearing and race on the outer bearing.

The 12 bolt Chevy and 8.5 10 bolts use a larger 30 spline pinion shaft for better oiling and just plain beefier hunk of metal.

Axles - the 12 bolt olds in 67 68 did have the advantage of larger axles and the 12 bolt olds uses a clutch type posi unit which is fully rebuildable 28 spline was the stock size and all the BOP bolt in axle depending on the year are interchangeable.

1964-1965 1966 sealed bearings axles 29 1/4"
1967-1968 sealed bearing axles 29 3/4"
1969-1972 non sealed bearing axle external seal on the shaft 29 3/4"
exception-
1971 -1972 Buick skylark and olds cutlass use non sealed but are 45 degree spline 29 3/4"

If the rear is assemble correct you surely will be surprised the punishment the diff can handle. OF coarse trans brake and 4000+ stall on a heavy (4000# and up) vehicle will really push the limits.

Aftermarket gears and axles and posi will always strengthen most all rears from stock parts.



Best to always sit down a realistically figure what the cars main use will be and how much power has to be applied to get it done.

STREET APPLICATION- If your mostly on the street most all muscle car rears 10 bolt 12 bolt etc. will do the job for a good long time with a proper rebuild.

'O' type suggestions with unlimited funds-
-MOSER 31 spline axles -a must
-Full spool would be best BUT if your street bound rebuild the 'O' type posi and shim aggressively on the clutch pack and aftermarket preload spring kit.
-aftermarket gears from Richmond 3.90ish
-all new bearings - of coarse
-weld the tubes to the center

That would be the best hands down.

Power trax could work for you also in a open if you can not find the posi BUT we have the 31 spline issue. I do not know if power trax could build a custom side 31 spline set for it. OR you could use 30 spline custom moser axles and the 8.5 power trax 30 spline. That would be strong and streetable too.

I have many ways we can go, but seems for most money is the issue. Jim


Jim Mitschke

Jim -
Need your "expert" opinion on something a "friend of a friend" tole me today about Richmond 4.10 gear set that was made for the 671 carrier. He claims you can machine .100 off the ring gear and use it on the 672 carrier without any problems? have you done this? Is this an option way to go for me to get into a 4.10 gear? Also I have been offered a drum-to-drum housing w/ 4.33 posi for $900. This is also an option, but going with the machined down 4.10 for my rear would really least costly approach for me - eh?
Heres what he "says" --
"The 4:10's were made for awhile,from Richmond,but I think they stopped awhile ago. They made the ring gear thicker,to use with the 3:08/3:23 carrier,but after some extensive R&D,I found that you can mill .100" off the backside,& that will put them where they need to be.The bolt hole depth is not a problem either.Richmond makes their holes deeper,so even after the milling,there is still plenty of depth for the bolts.I have been doing this for quite awhile now,so there aren't any doubts about it.I have some pictures of a build I did with these gears(milled). You can check with Smitty too.He knows I'm good.If you want to keep your housings & such,I'll just trade you your 3:42's for my Richmond 4:10's.If you need me to get them machined,let me know.I have not done them yet,but I could.If you have any other questions,let me know."

Whaddya think??
LMK
Tweed

You know I did hear that also. The only concern that I WOULD have had was the depth on the ring gear bolts...BUT if you say they are deep enough I do not see why that would not work.

I do have a Machining shop here that does all my other odd ball custom work because one they are very good at what they do and 2 I just do not have the time...lol.

Sounds like a winner. Jim

Thanks -
Think thats the direction i will head.
t.

Here if you need anything on the work. Jim