From: Bob Ternes (racecadet@yahoo.com)
Date: Fri Apr 22 2005 - 10:48:04 PDT
Dear List,
Erik has some really good points, but there's
something that came to mind as I read and re read
this email. I don't know if it's especially
salient to the list at large but here's one
viewpoint on GM tranny swaps.
The TH400 and its newer incarnations, the 4L80
and 4L80e, are great, strong trannies, but like
any "slushbox", there are parasitic losses in the
very nature of the technology, and the TH400
itself takes somewhere on the order of 20HP just
to spin. Simply due to size, the 4L80e is going
to be alot of HP to spin. This is mostly moot
when the coverter's locked up but until that
time, you're going to be slinging alot of ATF
around just to get up to speed. Also, 4L80's are
spendy trannies because of both supply and
demand.
Now, a 700r4 can easily be built to take abuse,
and alot of abuse, and is alot more efficient
from an energy consumption / parasitic losses
standpoint. I won't delve into the finer details
of what generation cases you want to look for and
what needs to be done, but parts are cheap and a
good tranny builder can point you to the parts
you want to use... and this is definitely a
shadetree job (with video or manual) if you know
a snapring or two from a hole in the ground.
700r4's are also a dime a dozen (comparatively).
Heat is really what kills auto trannies, so make
sure you run a 700r4 with an external cooler.
Also, rebuild with the right parts, and you won't
run into the classic 700r4 problems, which stems
from the deservedly bad rap from some bad designs
that didn't get fixed until the 1987-88
timeframe. As well, go aftermarket with your
clutches and shells and solenoids and whatnot and
you can have a tranny that will outlast and
outgrunt your stock hydramatic 400.
Finally, and what really pushed me over the top
on posting this, the 6.2 is a dog. There, I said
it! Anemic oil burner it is, in my opinion. You
CUCV guys need all the power you can conserve.
Mating that mill to a big slushbox, and then
pumping the power out to heavy, friction-bound
6000ft-lb-peak axles (save for the M1009) is part
of the reason those aren't stellar accelerators.
It's for that reason that I'd be personally
curious to see what the benefit is to mate up to
the 700r4, and why I typed this up.
Also, tcases for the 27 spline 700r4 output are a
dime a dozen, and there is decent enough demand
for a, say, 32 spline (which is the TH400 and
4L80e outputs) NP205 for it to fetch $300 to the
right person. NP203 is slightly more expensive. I
honestly don't know what they stuck in the
CUCV's, but I want to say 205?
Just some ideas. I'm cheap as heck and when I
needed a tranny to take and transfer the most out
of my 350ft lbs mill this fall, I went with a
rebuilt 700r4-type tranny. It made the most
sense. If you're towing a 25' gooseneck around
day in and day out, then you should probably
stick with the 1 ton stuff but for a town and
parts runner, a slightly built 700r4 wouldn't be
a bad choice.
Just don't forget to run a TV cable (or you'll
cook your box within a week!), and check
www.700r4.com . :)
Just brainstorming. I hope this doesn't waste
anyone's bandwidth. I got real familiar with the
700r4 this fall so hopefully this helps someone.
Some pages I found to explain the lineage and
differences:
http://www.chevyhiperformance.com/techarticles/46140/
http://www.rodandcustommagazine.com/techarticles/82558/
Or just go to a standard gearbox. ;)
Cheers
Bob Ternes
Proud owner of a 6'x6' pile of GM trannies and
transfer cases
--- Erik Lundquist <Erik_lundquist@hotmail.com>
wrote:
> Chris, you have a couple of options. You can
> get an after market over drive
> such as a gear vendors unit. Or replace the
> th400 with another GM over drive
> tranny such as the 700r4 or 4l80e. the 700r4 is
> a lighter unit and I
> personally don't think they are up to the task
> in anything but a 1/2 2wd
> truck or car. if you went with one of those you
> would have to change the
> transfer case to along with it. The 4l80 is
> basically a 4 speed
> electronically controlled th400. you can reuse
> the transfer case but you
> need to buy the transmission and tranny
> controller for it to work. With any
> of the 3 you will have to have new drive shafts
> made or your existing ones
> altered. I personally went with a 4l80, and
> kept the costs down by buying
> all the parts I needed on eBay and the local
> salvage yard. the Gear vendors
> are neat because you basically can overdrive
> all your gears making it a 6
> speed. If you have access to a machine shop or
> have a buddy that does I have
> seen Volvo over drive units used you just need
> to fab up the adaptor. If you
> have any questions let me know.
>
> http://www.gearvendors.com/
>
> Cheers,
> Erik
>
> PS. does anyone know the proper way to post,
> every I try to post something
> to ask a question I get the following message
>
> Failed to deliver to '<mil-veh@mil-veh.org>'
> LIST module(list mil-veh@mil-veh.org) reports:
> Your message cannot be posted.
> It has the content-type:
> multipart/alternative,
> and this list accepts text only
>
> "Our country won't go on forever, if we stay as
> soft as we are now. There
> won't be any America - because some foreign
> soldiery will invade us and take
> our women and breed a hardier race." LtGen
> Lewis B. "Chesty" Puller USMC
> ----- Original Message -----
> From: "Chris Brunner" <cjbrunner@optonline.net>
> To: "Military Vehicles Mailing List"
> <mil-veh@mil-veh.org>
> Sent: Thursday, April 21, 2005 8:27 PM
> Subject: [MV] CUCV - Overdrive?
>
>
> > Anyone know of a company that makes overdrive
> units for the CUCV? I'd
> > like to drop my RPM's when on the highway but
> not sacrifice the gear
> > ratio's. I'm working with a M1028 but I'm
> sure others out there might be
> > interested too.
> >
> > Chris
> >
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