700R4 Recommendations
Burning Brakes
Joined: Jul 2017
Posts: 1,114
Likes: 149
From: Frisco TX
I was not sure either. It may be the difference between the car version and truck version.
Instructor
Joined: Oct 2016
Posts: 150
Likes: 25
From: Acton MA
I did this a little over a year ago in my 81 and it was an awesome upgrade. Did the BTO crossmember and shifter detent kit and everything else can be sourced pretty easily. Others have already noted, but be ready to do some rear end gears after the swap. The highway cruising is great.
Engine / Trans swap with notes on the rear end gear upgrade
I was told to get one from late 88 up to 92. The rear planetary set was one of the weak spots and they(GM) fixed that in late 88 model year.
Engine / Trans swap with notes on the rear end gear upgrade
I was told to get one from late 88 up to 92. The rear planetary set was one of the weak spots and they(GM) fixed that in late 88 model year.
Race Director
Joined: Mar 2016
Posts: 14,402
Likes: 8,209
From: Napa Valley California
I went round and round with this issue when I was planning out the resto/mod of my 73.
With my cam specs and 3.08 rear gears I found I would be lugging the engine in OD at 1800 rpm @70 mph.
I ended up tossing the idea of installing an auto overdrive transmission with a .7 od gear because I did not like the idea of a difference of over 800 rpm between third gear and forth gear.
For me the perfect combo was swapping from my TH400 with 3.36 rear gears to a TKO600RR 5 speed manual with a fifth gear ratio of .82 and installing 3.08 rear gears.
The TKO600RR has a first gear ratio of 2.87 which is close to perfect and with the .82 fifth gear and 3.08 rear gears my cruising rpm is about 2180 at 70 mph.
The other thing I like is with the .82 fifth and 1.0 fourth gear there is only about 400 rpm difference between fourth and fifth.
Perfect for down shifting on an incline or driving in slower traffic at 60 mph in fourth gear.
Yes the swap is twice the cost, but I saved my pennies and got a kit through Silver Sport Transmission which included everything you need.
You can also justify the additional cost if it helps you from having to swap out your rear gears next year.
With my cam specs and 3.08 rear gears I found I would be lugging the engine in OD at 1800 rpm @70 mph.
I ended up tossing the idea of installing an auto overdrive transmission with a .7 od gear because I did not like the idea of a difference of over 800 rpm between third gear and forth gear.
For me the perfect combo was swapping from my TH400 with 3.36 rear gears to a TKO600RR 5 speed manual with a fifth gear ratio of .82 and installing 3.08 rear gears.
The TKO600RR has a first gear ratio of 2.87 which is close to perfect and with the .82 fifth gear and 3.08 rear gears my cruising rpm is about 2180 at 70 mph.
The other thing I like is with the .82 fifth and 1.0 fourth gear there is only about 400 rpm difference between fourth and fifth.
Perfect for down shifting on an incline or driving in slower traffic at 60 mph in fourth gear.
Yes the swap is twice the cost, but I saved my pennies and got a kit through Silver Sport Transmission which included everything you need.
You can also justify the additional cost if it helps you from having to swap out your rear gears next year.
Last edited by OldCarBum; Nov 13, 2019 at 12:12 PM.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
I did this a little over a year ago in my 81 and it was an awesome upgrade. Did the BTO crossmember and shifter detent kit and everything else can be sourced pretty easily. Others have already noted, but be ready to do some rear end gears after the swap. The highway cruising is great.
Engine / Trans swap with notes on the rear end gear upgrade
I was told to get one from late 88 up to 92. The rear planetary set was one of the weak spots and they(GM) fixed that in late 88 model year.
Engine / Trans swap with notes on the rear end gear upgrade
I was told to get one from late 88 up to 92. The rear planetary set was one of the weak spots and they(GM) fixed that in late 88 model year.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
You do not want...or need....an overdrive automatic trans in a car with a 2.87 rear gear. You will not be able to leave the car in Drive range until you get past 40 mph. Even then, it may do some 'lurching' when you need to apply light throttle for going up hills or under mild acceleration which does not cause a downshift.
I'm at a loss for understanding what you think an O/D transmission will do for your car. As is, you get over 20 mpg on the highway and cruise in relative comfort...compared to other C3's with 3.36 or higher (numerically) rear gear. Leave the O/D tranny swaps to those who actually need it. You really don't.
I'm at a loss for understanding what you think an O/D transmission will do for your car. As is, you get over 20 mpg on the highway and cruise in relative comfort...compared to other C3's with 3.36 or higher (numerically) rear gear. Leave the O/D tranny swaps to those who actually need it. You really don't.
If you play with the springs and weights on the governor, you can really dial it in,
My 1st gear is not as fast to shift like others, and it rarely goes 4th unless I am on the freeway.
If I floor it, (at 60), it drops to 3rd.
With a small cooler, it runs very cool.
Advanced
Joined: Nov 2018
Posts: 94
Likes: 55
I have a Monster 700r4 in mine. I have a 336 rear end and it feels right. Quick from a stop and cruises pretty well with the locking torque converter. I drive it to work on the interstate at 75-85 mph, and it does great.
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
Check out Silver Sport Transmissions. They offer complete packages with all the miscellaneous parts included (even the driveshaft). I plan to upgrade my '73 over the winter using their A41 kit which uses a 4L60E (electronically controlled version of the 700R4 so no TV cable needed). Plus you can set your own shift points.
DC
DC
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
I'm a big supporter (and owner) of the 700R4 conversion from a THM-400.....but I have a 3.36 rear gear. AFAIK, it perfect for what I want for my car. But, unless the OP wants to drive around the city in 2nd or 3rd gear and make gear changes at low speeds, the auto O/D is better matched with a 3.08 (minimum) to a 3.73 rear gear, IMO. I felt it necessary to share that before the decision is made and money spent. The OP needs to make his/her own decision after hearing various perspectives on the proposed change.
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Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
DC
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
I guessed that you were doing things one at a time when I read your first post. Transmissions usually is first because higher gears without it can wreck the highway driving ability. So, even though the rear gear isn't great, I figured you'd address it later if you decided you needed to.
I personally would use a 4L60e. They cost more mostly because of the controller, but the advantage of being capable of setting up the shift curves and converter lockup curves exactly as wanted is too much to give up when considering the money and time spent to do the swap. Having both speed and throttle used to control converter lockup is way, way better than most methods used on a 700R4. I tried the recommended "use a 4th gear pressure switch and just lock it any time it's in 4th" once and I can't post the words I'd use to truly describe how terrible I thought that worked. I switched that application out to a 4L60e and worked on the shift curves and TCC lockup curves and the car is awesome to drive now.
Over the years, I've read lots of bad comments about Monster and BTO transmissions. The BTO supporting parts are great though. Go to the 4th gen Camaro forums or LT1/LS1 forums to see who's building good transmissions these days.
I personally would use a 4L60e. They cost more mostly because of the controller, but the advantage of being capable of setting up the shift curves and converter lockup curves exactly as wanted is too much to give up when considering the money and time spent to do the swap. Having both speed and throttle used to control converter lockup is way, way better than most methods used on a 700R4. I tried the recommended "use a 4th gear pressure switch and just lock it any time it's in 4th" once and I can't post the words I'd use to truly describe how terrible I thought that worked. I switched that application out to a 4L60e and worked on the shift curves and TCC lockup curves and the car is awesome to drive now.
Over the years, I've read lots of bad comments about Monster and BTO transmissions. The BTO supporting parts are great though. Go to the 4th gen Camaro forums or LT1/LS1 forums to see who's building good transmissions these days.
Drifting
Joined: Aug 2019
Posts: 1,510
Likes: 498
700’s have a weak Lock up Converter that barely held up back when 230 hp was considered good power , the late model 88 and up 700’s were the better units because they have an Auxiliary Valve Body that incorporates a Boost Valve that bumps up line pressure for Third gear clutches , not sure on the planetary but they really need the Boost Valve in higher HP engines .
If you drive hard the 4L70e has a powerful Lock Up Unit , the Bell Housing is 3/4 deeper to allow a much much stronger Lock Up Clutch inside the Converter and you get 7 shifts if you’re on the gas , 1st then 2nd , 2nd Lock up then 3rd followed by 3rd Lock up then 4th gear followed by 4th gear Lockup just like a modern car
if you do go Electronic you can control everything with this https://www.usshift.com/usq4.shtml?g...iABEgLlOfD_BwE
If you drive hard the 4L70e has a powerful Lock Up Unit , the Bell Housing is 3/4 deeper to allow a much much stronger Lock Up Clutch inside the Converter and you get 7 shifts if you’re on the gas , 1st then 2nd , 2nd Lock up then 3rd followed by 3rd Lock up then 4th gear followed by 4th gear Lockup just like a modern car
if you do go Electronic you can control everything with this https://www.usshift.com/usq4.shtml?g...iABEgLlOfD_BwE
Last edited by Eric P; Nov 16, 2019 at 12:07 PM.
Pro
Joined: Jun 2005
Posts: 583
Likes: 61
From: USA
AFAIK, the passenger car 700R4 tailshaft housing (e.g. Caprice) is the shortest of the conventional housings that don't have the C-beam or torque-arm boss. But even that one still makes the 700R4 a little longer than the TH350, requiring a shortened drive shaft. I forget the exact DS shortening dimension, but I think it was less than an inch. so long ago. I had a custom one made up by Dennys Driveshafts.
Melting Slicks
Joined: Nov 2017
Posts: 2,358
Likes: 519
You probably already know this, but a little over emphasis is better that the alternative. A buddy of mine burned up his overdrive trans before he even backed it out of the garage. 
Make triple sure you set up your TV cable correctly using a pressure gauge. Pressure has to rise the moment you tip in on the throttle.
While you are there, take a pressure reading in all gears.
Also, I highly recommend the TV Made EZ from Bowtie Overdrives.
Make triple sure you set up your TV cable correctly using a pressure gauge. Pressure has to rise the moment you tip in on the throttle.
While you are there, take a pressure reading in all gears.
Also, I highly recommend the TV Made EZ from Bowtie Overdrives.