FWD vs. RWD patterns

[Steve Ochs]

Message text written by INTERNET:Shannen
>
  Sorry guys, but I have *got* to disagree.  That's one thing technicians
and
engineers do. :)  I work on these things daily and I will say that 2.8 and
2.5
used in RWD does not have traditional Chev bolt pattern. I'll send photos
if I
have to, but no way are they the same.  Original "Iron Duke" 151 has Chev
pattern, but not newer vers.  Trans is cast with different or dual type
bolt
pattern.  Only other note that should be added is that the new rating
system
for trans is broken down similar to following example.<

Forgot to include the designation system in my note.  Also, I am less an
engineer and more of a tech.  Been working on and repairing cars for 24
years.  

Notice I did not include the 2.5L 4 cylinder (Iron Duke) in my statement
because I don't believe it was originally available with the 700-R4 in the
trucks. It came with the THM-200C tranny or the 3L30 which definetely had a
different bolt pattern (the Iron Duke was a Pontiac design from the 60's
and had a BOP pattern?). The later 2.5L TBI engine in the early 90's came
with the 4L60 tranny but I do not know what bolt pattern.

We did make dual pattern transmissions (200-R4, 250-C, 200-C) but I don't
rememeber a 700-R4 dual pattern case.  

As far as I remember, the 2.8L V-6 in my 1984 Jimmy had a standard 700-R4
Chevy bolt pattern.  I know the truck 2.8L is not exactly the same as the
passenger car 2.8L although they were very similar (cast iron heads vs.
aluminum, etc.)  I could be wrong.  

I would really appreciate a photo of the 2.8L and 2.5L 700-R4 bellhousing
pattern.  As I said, all of the information, Technicians manuals,  and
drawings that I have avaialble (which is pretty limited before 1987) and
may not be all inclusive show only a Chevy RWD bolt pattern on the 700-R4. 
I would like to see what this pattern really is if it is a FWD pattern or a
modified Chevy RWD.  

Steve Ochs aka N8TYS- Mfg. Engineer - GM Powertrain - Parma Plant
Transmission Division (4T60/65-E) - Steve_Ochs at compuserve.com
The statements and opinions expressed here are NOT an official
statement of General Motors or the GM Powertrain Division

'97 Chevy Blazer LT 4x4 4.3L V6    '96 DCM Impala SS 5.7L V8 
'87 Olds Cutlass 442 307 V8        '61 GMC 1500 Fleetside 305 V6