63mako

With a 3.08 rear gear I would go 700 R4. It is not much more work to change over. How do you like that cam?
http://www.oldengine.org/unfaq/leadfoot/trans.htm

Mashman

It all depends on how much you spend, and how much, and how you drive your car.

I drive ~ 7000 miles per year, mostly highway miles, and I average ~ 12 MPG. So I use around 583 gallons per year.

If after the conversion I got ~ 20 PGM, that would save me 233 gallons per year. If the average cost of gas is $3.20 per gallon, that means I would save $745 per year on gas alone.

If I spent $1500 on the project - a very reasonable budget with a rebuilt trans, and installing myself - I would recoup the cost of the project in only 2 years. This does not include the long term saving based on reduced engine wear by running 700 fewer RPM. There's also the added comfort level of running fewer RPM.

I live in Texas and drive my car whenever I can. I don't commute with it because I work from home, but if I have to go anywhere, and it's not raining, I drive it, that's about 150 miles per week. If you live up north, and are only able to drive your car a few months out of the year, then maybe it might take a long time to recoup your costs, but I don't think that's the case with the OP. It looks like he has a climate very similar to mine.

riverracer au

yeah we have hot n dry summers here, and where i am, none of that white powder that fall from the sky, ever...

the 700r4/4L60 is a trans that i can get down here, as it was used on mid 90's GM Holdens.

i have found sites where builders are building them lockup or non-lockup..
if you dont use the lockup feature, the fluid only has limited access to the cooler ports,
only in lockup mode do the ports open up fully to the cooler.
but a non-lockup trans gets full cooling all the time.

is that a good idea/option?

from what i can gather the lockup only drops it a couple hundred more revs.

is lockup worth the extra hassle in the long run with my 3.08 rear, which would drop the revs very low?

so, if im doing 2700revs and overdrive on a 700r4 is 0.7 thats 1890revs, or a 200-4r is 0.67, 2700revs is 1809revs.

thoughts?

63mako

700 R4 has better 1st gear for your 3.08, needs less convertor stall because of the gearing. runs cooler with less stall, and is a little more rev to help keep you in the powerband better at cruise. Lockup 200 RPM less cruise gets better mileage. Heat kills transmissions. I would go 700 R4 with lockup, manual lockup if you want. The 4L60 is a different deal. Needs ECM.

riverracer au

what i found on both,
In 1990, the Turbo Hydra-Matic 700R4 was renamed the 4L60. Under the new designation,
the "4" stands for the number of forward gears, the "L" for longitudinal applications (rear-wheel-drive),
and the "60" is the strength rating.
The 4L60 however is hydraulically shifted based on governor pressure and TV cable position
1992 was the last year of widespread usage of the 700R4 (4L60).
1993 Camaro, Corvette and Typhoon were equipped with the last production 700R4's.
The "E" denotes electronically controlled shifting.
In 1992 electronic controls were added, and it became the 4L60-E.

edit:
turns out the local built 5L (304ci 268hp) GM Holden Commodore built between 1988 and 1994 used the th700,
late production used the 4L60, cable pull, and they had a 3.08 diff as well.
more investigating to be done.

7T1vette

The 200-4R swap for the THM-400 is easier than the 700-R4, as you can still use the stock cross-mount bar. The 3.08 rear gear should not be much of a problem. It will be fine at highway speeds, as your engine will only be turning 1800 rpm at 70mph and you should get great highway mileage. In the 30-45 mph range, you may want to keep the trans in 3rd gear, so that you don't get any 'bucking' from low rpm's at those speeds.

Another 'plus' is that the 3.08 gear will allow the O/D trans low gear to be of some use; O/D trannies with steeper rear gears have little use for that low range in the tranny.

You will need a lockup controller of some type to allow that unit to work properly without damaging it. I built a unit for about $25 from auto parts store items that works fine: it engages with a [momentary] push-button and disengages with a tap of the brake pedal. The only other condition you need to manage is that lockup should be dropped whenever you want to stab the gas when at highway speeds (like when passing). You just need to tap the brake pedal (not apply the brakes) before you go WOT so that the torque spike won't damage the lockup clutch.

Send me a PM with your e-mail address if you want me to send a copy of the controller circuit I built.

riverracer au

email received 7T1.

have had a couple of quotes come in, $900-$1100 for shipping to Australia.
plus the cost of a trans, at around $1400, makes this a rather expensive exercise if i went the 200-4r way.
i liked the 200-4r path, easier swap, same tail shaft and X member etc.
but with those shipping costs i think i'll look at the 700r4 from local cars, and just buy the X member, tv cable etc from over there.
still looking at 500$ish for a box out of a wreck here, plus rebuild etc.
should be able to find a 2nd hand c3 tailshaft that i can shorten to keep the original if i sell.

decisions, decisions

or maybe i'll just have go on shorter drives, avoiding long runs......

aussiejohn

G'day,

I use Ameroz to ship my Borgeson steering boxes and they charge $185 per cubic metre, so you should not be paying more than that for shipping (on a SHIP). The price you were quoted was probably UPS air freight, not sent on a ship. Feel free to ring me on 03 9502 3227 if you want more info.

Regards from Down Under.

aussiejohn

Haggisbash

Hi RR, have you pulled the trigger on a transmission yet?