Re: [Amc-list] Early 80's 4-cyl bellhousing

[Frank Swygert <farna@xxxxxxx>]

Yes, the 2.5L was paired with a T-5, but the trans and rear axle gearing were set up for it also. Anyone who had one will probably tell you fifth gear was useless unless you were on the interstate running 60+ with a light load and in pretty level terrain. I've driven a couple late 70s/early 80s cars/trucks with small engines and five speeds. In a rural area, especially with hills, you never use fourth gear, and don't use it a whole lot on the freeway -- almost always have to gear down to maintain speed up grades of any inclination or length. 

I've driven OD cars too. I agree -- the 199 can handle pull an OD by 45 mph (not much before though!) with a 3.08 gear, but it would likely get better mileage in most areas with more gear. I went from a 3.08 behind my 4.6L with AW-4 (0.70:1 OD -- same as the old BW units) to a 3.55 gear and gained 2 mpg on the highway. The engine would easily pull the OD gear, but rpm were under 2000 around 65-70 and the engine was working harder. Not struggling by any means, but obviously working harder. I checked my mileage on a long trip -- from Gulfport MS to Kenosha in 2002 -- with the 3.08 gears and was sorely disappointed. When I rebuilt the car (it was wrecked just a couple days after the trip) I wanted 3.31 gears but ended up with 3.55 by "mistake" (bought a used set, seller couldn't do math or just wanted to sell!). I was happy once I checked mileage on trip from Gulfport to SC and back and got 2 mpg more. Not sure if 3.31 would be better or not, but surely couldn't be more than 1 m
 pg better on the highway, and I do like the pickup with the 3.55s!

-------------
Date: Wed, 8 Oct 2008 18:30:50 -0400 (EDT)
From: adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)


" From: Frank Swygert <farna@xxxxxxx>
" 
" BAD IDEA!! That little four (a 2.5L GM "Iron Duke" in your case)
" doesn't have the torque to pull an OD. It probably doesn't have enough
" to pull an OD five speed either. The OD gear in most five speeds is
" similar to that of the old ODs, so if you do go this route do yourself
" a favor and find a T-5. In either case you'll need a lower rear axle
" ratio to pull the OD.

but...  the s10/blazer, which must be similar in weight, paired the
iron duke with t5s...

" A common misconception is that OD adds a higher gear -- it does just
" the opposite. Check the books for any old car with a three speed and
" OD and you'll find that it used a much lower rear axle ratio than a
" car with a standard three speed. OD reduces rpm in a street/strip car
" that's set up to run on the strip without using OD, that's why people
" think it's such a great thing! That's not the case in a pretty much
" factory stock car though. 

not always true.  standard axle in a late '60s american with 199/t96
was 3.08, but o/d could also be had with 3.08.  okay, this is a notch
lower than the optional 2.73 without...  but even with the 3.08, o/d
was set to engage at 38 mph!  from my own experience, the 199 is
definitely ready by 45.

from my limited data, in the late '60s o/d axles were only one notch
lower than without.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)


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