best '72 auto trans for fuel saving
Thread Starter
Melting Slicks
Joined: Oct 2010
Posts: 2,276
Likes: 337
From: "ɹǝpunuʍop", Adelaide, South Australia
best '72 auto trans for fuel saving
ok, i just got back from a 2000km (1240mile) 9 day trip.
went thru a crap load of fuel as it doing around 2700 at about 110km/h (your 70m/h).
so had time to ponder what to do, answer, mite look into an overdrive trans.
yes there are many posts on here, but i have a few questions,
i see a lot recommending 200-4r or the 700r4.
i have the following,
1972 - 350(+.020"), howards 111145-12 retrofit hyd roller cam, quadjet with performer manifold,
3.08 rear, 235/60r15 tires and has th400 now.
so which is the better trans for my setup with a 3.08?
which is easier to do?
do both need to have the tailshaft shortened?
what's the best way of doing the lock-up?
will i need a new torque convertor?
does the original shifter and cable fit or need new setup?
how much of a rpm drop would i expect to get?
as i'm down under, is there a complete list of all the required parts i'll need to source and ship here?
went thru a crap load of fuel as it doing around 2700 at about 110km/h (your 70m/h).
so had time to ponder what to do, answer, mite look into an overdrive trans.
yes there are many posts on here, but i have a few questions,
i see a lot recommending 200-4r or the 700r4.
i have the following,
1972 - 350(+.020"), howards 111145-12 retrofit hyd roller cam, quadjet with performer manifold,
3.08 rear, 235/60r15 tires and has th400 now.
so which is the better trans for my setup with a 3.08?
which is easier to do?
do both need to have the tailshaft shortened?
what's the best way of doing the lock-up?
will i need a new torque convertor?
does the original shifter and cable fit or need new setup?
how much of a rpm drop would i expect to get?
as i'm down under, is there a complete list of all the required parts i'll need to source and ship here?
Last edited by riverracer au; Nov 2, 2014 at 10:38 PM.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
I just did a 1300 mile trip with mine, had a best mpg of 20.1. I replaced my TH400 with a 2004r. I had a 3.08 rear gear originally, but switched to a 3.55 because the rpms were too low. Now I cruise at 80 mph at 2200 rpms. I would think the 3.08 gear will be too high with either of the overdrives.
No drive shaft shortening with the 2004r.
No drive shaft shortening with the 2004r.
Drifting
Joined: Jan 2006
Posts: 1,832
Likes: 38
From: Cedar,BC
If you are looking to save money,you won't- it will take decades to get a return on your overdrive conversion.However for many just the quieter and more comfortable ride with the OD on the highway makes it worthwhile.
Safety Car
Joined: Aug 2001
Posts: 3,685
Likes: 202
From: Waterford Mi
I also installed the 200-4R in my 73 with 3.55 gears. I needed to replace the TH400 anyway because the seal area for the trans pan would not seal and I always had a real bad oil leak that several tries would not fix. Before the change I was lucky to get 11-12mpg. Now I get about 18mpg. I did not expect the savings to pay for the change but I like the fact that it is a lot easier on the motor and drive line. I drive about 70miles a day to work and the trip to the NCM is a lot nicer every Labor Day Weekend.
Thread Starter
Melting Slicks
Joined: Oct 2010
Posts: 2,276
Likes: 337
From: "ɹǝpunuʍop", Adelaide, South Australia
not looking to re-coupe the overall costs in fuel savings, just use less fuel on long trips.
i did a few quick sums, and i was getting about 16mpg...
not too good when some of our outback fuel stations are far apart.
so the 2004r is a direct bolt in, no shorten tail shaft required.
will need to find someone that will ship downunder for a fair price.
i did a few quick sums, and i was getting about 16mpg...
not too good when some of our outback fuel stations are far apart.
so the 2004r is a direct bolt in, no shorten tail shaft required.
will need to find someone that will ship downunder for a fair price.
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
200r4 with 3.08 from Bow Tie Overdrives, suggestion; get the trans cooling lines they offer. The upgrade is outstanding. Look over their website, they offer a complete conversion kit for the C3s. T
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Melting Slicks
Joined: Oct 2010
Posts: 2,276
Likes: 337
From: "ɹǝpunuʍop", Adelaide, South Australia
Melting Slicks
Joined: May 2012
Posts: 2,192
Likes: 343
From: Allenton Wisconsin
You're right no kits listed , I revisited their site. If you call them & tell them what you're looking to do they'll make up a parts list and sell it as a kit to you. Make up a list of questions you have & you need all the specs of your car [tire size, carb type, gear ratio, engine HP, etc]. In regard to your question about converter lock up, mine with the 3.08s doesn't come in until over 65mph because of the low rpm. The converter I got was a 2200rpm stall and I'm at 2100rpm at 65 with 25.5 tall tires. T
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
My 200R4 behind a std 350 with 3.08 rear 1800 - 2100 stall, shifts into 4th at 80kmh when travelling on level ground, my lock up is vac controlled so will lock as soon as 4th is selected but unlocks when manifold vac is high such as travelling downhill or idling ( I also have a manual override switch) I am going to change to a 3.55 rear as 3.08 is too big a gear to be practical here most of the time. In our hilly terrain I have to often lock the trans in 3rd. 1600 rpm = 100kmh when locked in 4th, 3000 rpm = 160kmh.
Thread Starter
Melting Slicks
Joined: Oct 2010
Posts: 2,276
Likes: 337
From: "ɹǝpunuʍop", Adelaide, South Australia
do you have to connect the lock-up function at all?
i have read that it will drop the revs to much, extra 200ish, and because of the 3.08 rear, that it will hunt in n out alot under load.
or will that cause other problems if lock-up is not used?
3rd in the 200-4r is the same as "d"on the th400, 1:1
so if it was left in 3rd around town and only used the 4th/od on country drives or above a certain speed,
it should be fine shouldn't it?
so if i came to a hill or needed to pass in 4th/od, put my foot down/booted it, it would drop back a gear like normal....
or am i looking at this all wrong?
would have looked at the b&m speed activated controller if needed.
everyone talks about home made controllers using on/off switches, relays, timers, vacuum switches etc.
but i haven't found any actual printed circuit diagrams showing/comparing how it's done...
i have read that it will drop the revs to much, extra 200ish, and because of the 3.08 rear, that it will hunt in n out alot under load.
or will that cause other problems if lock-up is not used?
3rd in the 200-4r is the same as "d"on the th400, 1:1
so if it was left in 3rd around town and only used the 4th/od on country drives or above a certain speed,
it should be fine shouldn't it?
so if i came to a hill or needed to pass in 4th/od, put my foot down/booted it, it would drop back a gear like normal....
or am i looking at this all wrong?
would have looked at the b&m speed activated controller if needed.
everyone talks about home made controllers using on/off switches, relays, timers, vacuum switches etc.
but i haven't found any actual printed circuit diagrams showing/comparing how it's done...
Melting Slicks
Joined: Oct 2006
Posts: 2,417
Likes: 336
From: Texas
i have the B&M controller on my 2004r, it really takes alot of the guess work out of it, just set it with the dial at the speed you want it to lock up at and its automatic. if you dont want it locking at all you can turn if off with a pushbutton, simple. it comes with instructions on connection to trans. i have mine set at 60mph... trans shifts to 4th gear at about 50 then tq locks at 60. around town you can put the shifter in 3rd if you want then its like th350... but i leave mine in D most of the time.
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Definitely do a mildly built 200R4 behind a mild 350. It will accelerate harder and give better gas mileage.. A great mod for a car that drives on the highways a bunch.
CK performance, California performance transmission and BTO are all good options for 200R4s.
CK performance, California performance transmission and BTO are all good options for 200R4s.
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
do you have to connect the lock-up function at all? If you want to use the car on trips I would recommend you use the lock up and it is a different torque converter than std so make sure you get one that matches the transmission.
i have read that it will drop the revs to much, extra 200ish, and because of the 3.08 rear, that it will hunt in n out alot under load. It wont hunt in and out of lock up if set up correctly.
or will that cause other problems if lock-up is not used? You can overheat the trans if using 4th a lot without lockup.
3rd in the 200-4r is the same as "d"on the th400, 1:1
so if it was left in 3rd around town and only used the 4th/od on country drives or above a certain speed, That is what I do.
it should be fine shouldn't it?
so if i came to a hill or needed to pass in 4th/od, put my foot down/booted it, it would drop back a gear like normal.... Yes
or am i looking at this all wrong?
would have looked at the b&m speed activated controller if needed.
everyone talks about home made controllers using on/off switches, relays, timers, vacuum switches etc.
but i haven't found any actual printed circuit diagrams showing/comparing how it's done...
i have read that it will drop the revs to much, extra 200ish, and because of the 3.08 rear, that it will hunt in n out alot under load. It wont hunt in and out of lock up if set up correctly.
or will that cause other problems if lock-up is not used? You can overheat the trans if using 4th a lot without lockup.
3rd in the 200-4r is the same as "d"on the th400, 1:1
so if it was left in 3rd around town and only used the 4th/od on country drives or above a certain speed, That is what I do.
it should be fine shouldn't it?
so if i came to a hill or needed to pass in 4th/od, put my foot down/booted it, it would drop back a gear like normal.... Yes
or am i looking at this all wrong?
would have looked at the b&m speed activated controller if needed.
everyone talks about home made controllers using on/off switches, relays, timers, vacuum switches etc.
but i haven't found any actual printed circuit diagrams showing/comparing how it's done...
Thread Starter
Melting Slicks
Joined: Oct 2010
Posts: 2,276
Likes: 337
From: "ɹǝpunuʍop", Adelaide, South Australia
wow, BTO must be very busy...
sent some questions off over 2 weeks ago, still no reply.
that's just bad customer service in my book.
they have lost my bussiness, will look elsewhere now.
at least the ebay peolpe answered my questions in a couple of days,
and with a reasonable freight cost.
sent some questions off over 2 weeks ago, still no reply.
that's just bad customer service in my book.
they have lost my bussiness, will look elsewhere now.
at least the ebay peolpe answered my questions in a couple of days,
and with a reasonable freight cost.
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
wow, BTO must be very busy...
sent some questions off over 2 weeks ago, still no reply.
that's just bad customer service in my book.
they have lost my bussiness, will look elsewhere now.
at least the ebay peolpe answered my questions in a couple of days,
and with a reasonable freight cost.
sent some questions off over 2 weeks ago, still no reply.
that's just bad customer service in my book.
they have lost my bussiness, will look elsewhere now.
at least the ebay peolpe answered my questions in a couple of days,
and with a reasonable freight cost.
but they did send out their TV cable kit straight away when I ordered it
Burning Brakes
Joined: Sep 2012
Posts: 818
Likes: 0
From: coon rapids mn
B&M sells the manual lock up kit .I drive around town in 3rd ,only use 4th and the lock up on the hi-way .don't apply alot of power with the trans locked up .if you race ,put it in 3rd .I love the way the 700r4 works with my car .luckily my cousin builds racing transmissions ,so I get them for cost .