I have a 69 442. It does not have a posi traction diff. I was thinking of putting one in and was wondering the rough cost. I don't know if I really need it. Would I be better off spending the money on disk brakes.Any opinions appreciated. Thanks

 

Hi,

As long as your not changing gears, posii, carrier bearings and maybe axle seals should be all the cost involved, depending on how many mile miles you have on it, pinion bearing and seal would be the other cost depending on condition.

Regards,

 

Do you run it at the drag strip ?
Do you drive it on snow and ice ?
Do you like to leave two black strips of rubber on the pavement ?

If not , "Save your money and buy whiskey ."

 

Your car likely has an O-Type rearend, so the choice of limited slip differentials is very limited (ha, there's a pun!)
The choices are:
1) used GM or
2) aftermarket machined Ford 8.8.
Be aware that the Ford 8.8 works only with 3.08-3.23 gear ratios, anything else would need a used GM differential.

 

Thanks for the replies. It wasn't going to take much to talk me out of it. It has managed to get by for 50 years with out one, I'm sure it can continue.

 

I was amazed when I learned back in the 80s that many performance cars didn't have a limited slip diff, even though it was a very inexpensive option when these cars were new. Also amazing to me was that my 1970 Cutlass Supreme with a 2.56 rear had a limited slip diff, when many 442s didn't get one.

 

My '68 4-4-2 came with a 3.08 limited slip differential. My '69 4-4-2 came with a 3.23 open differential. I converted the 3.23 to limited slip but I didn't do the work. Parts were around $800. Labor was another $500. That was done in 2015. I don't notice any difference in adding limited slip to the '69. I don't push either car hard at all. If I had it to do over again, I'd probably keep the $1300 in my pocket. Both cars have THM 400 transmissions. I got my limited slip kit from Supercarsunlimited.com.

Randy C.

 

I can see the rationales already shared by others as to why you might consider not going through the cost of adding the posi feature. That said, I own a 70-442 4 speed w/posi. If you have never felt the difference of sitting dead still or slowly rolling to the left while fully in gauging the gas pedal and feeling both tires begin to dance while soon after shifting into 2nd gear is a different feel of fun vs a non posi rear end in play. I don't do it often in my restored ride, but its a sensation that every muscle car fan should feel at least once.

 

Hell, do it on ice, and it's an awful feeling.

 

That's not true, I have a Richmond 3.90 on a modified Ford 8.8 w/ 28 spline axles in my '68 Type-O rear. Supercars Unlimited offer a variety of diffs for the Type-O.

 

^^^This. If you have a 3-series carrier, you can always use a shim or thick gear set to run higher numerical gears. The problem comes in the opposite direction. If you have a 4-series carrier, you cannot run gears lower (numerically) than 3.42.

 

You are correct, I didn't state that accurately. I was referring to the original poster's factory gears in his O-Type. The Richmond Gear ring gears are manufactured with the same thickness as the original 3.08-3.23 GM gear sets, so they work with a differential made for the original 3.08-3.23 gears.

 

My point is that if he currently has 3.42 or steeper gears, the converted 8.8 still works. He would simply need to use a spacer with the factory ring gear. I realize this is not ideal, but it works.

 

Not sure you even need a spacer to accomodate factory 3.42+ gears w/ this diff:
Or does the fact that this is a special order item mean that it is really a refurbished factory diff? I kind of doubt it though, as they offer a single clutch rebuild kit for all the diffs they offer, and I doubt that the same kit would work for both the modified 8.8 and the factory diff. I'm pretty sure all the diffs that SU offers are various modifications of a Ford 8.8.

 

Obviously if it's a 4-series carrier, you don't need a spacer to run 3.42 or higher numerical gears.

 

I would interpret the special order to mean a Ford 8.8 diff would be machined so the ring gear pad is thicker to accommodate the factory gears. Just speculation on my part, though. I'm sure monzazz or Brian Trick could enlighten us, if they were to read this topic.