I have a few comments for this week old thread...
On 20 10/19/05, cpollock@xxxxxxxx wrote:
> There are other differences between the 489 and the 741 (and 742). The
> biggest difference is that the pinion shaft is tapered, and adjusted by
> means of a crush sleeve, whereas the 741 and 724 are straight shafts and
> use shims for the adjustment of pinion depth. Both of these pumpkin (or
> center) sections were produced from the mid 60's to the mid 70's, and were
> mainly found under muscle cars. SO, they would not apply to your 58 at
> all, but are very commonly used as a retrofit. Some people on this list
> have done it and could tell you what you need.
>
> The 489 case is considered more durable, and able to handle torque better
> than the 741 and 2. 489 were generally found under cars that came with a
> big block engine, but not necessarily a high-output engine. The suregrip
> version of the 489 are very desirable, and, very expensive at this point.
actually, the 489 replaced both the 741 and 742 units around 1969/70.
the 741 was the lighter duty unit, used under cars like slant six Coronets,
318 Furys, and even some big block cars,, oh and tons of A100's and D100's.
the 742 case was tougher duty, and usually if the car came with a SureGrip
it was fitted with a 742. It was used in Hemi automatic cars, 440 & 383
cars, and C-bodies, and SG vans & trucks as well. The 489 was used in
everything from some 318-2bbl Dodge Darts w/ towing packages, to Roadrunners,
to D100's & vans.
> The 741 and 2 are very stout rearends as well, and can handle a lot of
> power. Generally they can be found for less than the 489. Both are common
> enough though that aftermarket vendors will carry a wide variety of parts
> for them.
>
> I really think the ultimate swap though is for the rear out of a 74
> Imperial, as they were big block cars, and- they had rear disc brakes.
didn't the Imp's have a 5x5" wheel pattern instead of a 5x4.5" wheel
pattern?
www.autohobbydigest.com/8_75.html is another doc. the pre-64 thrust block
sizing issue might pose a problem for some 742/741/489 swaps into forward
look 8-3/4" housings. It also has some housing width information for
complete housing swaps. If you want to keep the tapered axles, the 64
B-body & Chrysler rear might be a good unit to look at, if you want flanged
axles, the 65 & up C-body axles might be the way to go..
Doug Ahern
Athens, GA
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