Trans conversion
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Intermediate
Joined: Jan 2012
Posts: 45
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Trans conversion
I have a 72 stock small block with 3 speed auto trans,as I do lots of freeway driving I would like to install a 700R4 box for better fuel economy.will a 700R4 trans just bolt in with out any problems,apart from tail shaft length,any info would be helpful Thanks Alan
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,559
Likes: 7,006
From: New Or-leens Loo-z-anna
Click on these links:
https://www.corvetteforum.com/forums...ght=700r4+swap
https://www.corvetteforum.com/forums...ddly-bits.html
It might be cheaper/easier to change the ring and pinion gears in the differential to lower highway engine rpm.
https://www.corvetteforum.com/forums...ght=700r4+swap
https://www.corvetteforum.com/forums...ddly-bits.html
It might be cheaper/easier to change the ring and pinion gears in the differential to lower highway engine rpm.
Advanced
Joined: Jan 2007
Posts: 81
Likes: 0
From: Sacramento Ca
You also have to relocate the trans support brace. And no, changing gears isn't a better option. You lose the low end power. I have great low end and @ 1700 rpm I'm doing 70 mph and 16 mpg With 3.08 gears
Racer
Joined: May 2014
Posts: 420
Likes: 5
From: Springfield Missouri
The 700r4 is not a bolt-in swap: you have to relocate the transmission crossmember further rearward. If you want a bolt in automatic with overdrive, look into a 2004R. Plenty of info about it here in General and over in Tech/Performance. It's the most common swap since it's a bolt-in replacement.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
The 200 R4 is a better bolt in swap.
Slightly better overall gear ratio, same drive shaft length.
You will need a new trans mount and a Shifter kit so that the shifter will work.
Well worth the effort
Slightly better overall gear ratio, same drive shaft length.
You will need a new trans mount and a Shifter kit so that the shifter will work.
Well worth the effort
Racer
Joined: May 2014
Posts: 420
Likes: 5
From: Springfield Missouri
About the shifter kit, I just want to have this said for full disclosure, that way eurekax knows exactly what he's getting into. If you only ever put the car in D, then you don't need to get the shifter kit. However, you wont be able to manually put the new transmission into 1st gear as the existing shifter detent is only for 3 gears, not 4. If you want to have full access to all the gears in your new transmission, you'll need the kit. As a plus, they sell a little gear indicator showing you have 4 gears instead of the stock 3. Makes it look factory.
Shiftworks sells them, as does Bowtie Overdrives, though I think BTO just sells the Shiftworks kit.
Melting Slicks
Joined: Jun 2005
Posts: 2,239
Likes: 74
From: Palatine, Peoples Republic of Illinois
St. Jude Donor '09-'10-'11-12-'13-'14-'15-'16-'17-‘18
NCM Sinkhole Donor
Might want to try these guys: http://shiftsst.com/ . They make complete kits to fit the car. The are the ones who took over Kiesler after the bankruptcy. From what I understand they are great to work with.
Racer
Joined: May 2014
Posts: 420
Likes: 5
From: Springfield Missouri
Might want to try these guys: http://shiftsst.com/ . They make complete kits to fit the car. The are the ones who took over Kiesler after the bankruptcy. From what I understand they are great to work with.
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Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
I forgot about the driveshaft length. You're right: if he goes with a 700R4 he'll have to shorten the driveshaft in addition to relocating the crossmember. Thanks for bringing that up.
About the shifter kit, I just want to have this said for full disclosure, that way eurekax knows exactly what he's getting into. If you only ever put the car in D, then you don't need to get the shifter kit. However, you wont be able to manually put the new transmission into 1st gear as the existing shifter detent is only for 3 gears, not 4. If you want to have full access to all the gears in your new transmission, you'll need the kit. As a plus, they sell a little gear indicator showing you have 4 gears instead of the stock 3. Makes it look factory. Shiftworks sells them, as does Bowtie Overdrives, though I think BTO just sells the Shiftworks kit.
About the shifter kit, I just want to have this said for full disclosure, that way eurekax knows exactly what he's getting into. If you only ever put the car in D, then you don't need to get the shifter kit. However, you wont be able to manually put the new transmission into 1st gear as the existing shifter detent is only for 3 gears, not 4. If you want to have full access to all the gears in your new transmission, you'll need the kit. As a plus, they sell a little gear indicator showing you have 4 gears instead of the stock 3. Makes it look factory.
Shiftworks sells them, as does Bowtie Overdrives, though I think BTO just sells the Shiftworks kit.
Melting Slicks
Joined: Oct 2011
Posts: 3,453
Likes: 67
From: Midland Ontario
NCM Sinkhole Donor
Like the boys are saying, the 200 will be a much easier/happier way to go. Try contacting Bowtie Overdrives, as I haven't seen them mentioned yet. Pretty much a one stop shop for this conversion. Remember to document your conversion here with lots of pics.......we all love lots of pics.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
The THM-200-4R is a better trans to install in your particular vehicle. The stock crossmount bar and mount will still work with that trans. There are still quite a few mods that need to be made to get it installed and working properly. If you are going to do the work, you need to research this swap THOROUGHLY before initiating this project.
The 200-4R [or 700-R4] need to be upgraded for strength, they need to have the correct output housing configuration, need pan mounted brackets modified, need different fill tube mounting, and need the T.V. cable installed and adjusted properly. If you want lockup operation, you will need a lockup converter (selected to match your engine's needs) and it would be best to have a lockup controller to manage lockup operation properly.
It's a good swap...when you get it all done.
The 200-4R [or 700-R4] need to be upgraded for strength, they need to have the correct output housing configuration, need pan mounted brackets modified, need different fill tube mounting, and need the T.V. cable installed and adjusted properly. If you want lockup operation, you will need a lockup converter (selected to match your engine's needs) and it would be best to have a lockup controller to manage lockup operation properly.
It's a good swap...when you get it all done.
Melting Slicks
Joined: Oct 2010
Posts: 2,276
Likes: 337
From: "ɹǝpunuʍop", Adelaide, South Australia
one link Doorgunner posted, was to my 700r4 swap in my '72 that i'm in the middle of,
i did a lot of research on here and the net, but still have/had a lot of questions.
i've tried to cover all the "fiddly suff" that no one else covers...
https://www.corvetteforum.com/forums...ddly-bits.html
i didn't shift my x-member, just used a different case mount that puts it within 3/4" of a T400.
BTO sell a new x-member with the mount in the correct position, one less headache.
yes the driveshaft needs to be shortened, but no biggie in the scheme of things.
i bought the shiftworks "shifter kit" which includes a new detent plate, but i haven't installed it yet.
reading here, you can just notch your existing plate to enable 1st gear selection, but...
i have hooked my cable up with SW bracket that mounts onto the pan and i can select ALL gears, even 1st.
as i'm downunder, i went with the 700r4 (t700 as we call them) as they came in early 90's GM Holden cars down here.
otherwise i would be up for $$$ in shipping to get a 200-4r here.
ask as many question as you need.
ps: you've got same name as well, Alan...
i did a lot of research on here and the net, but still have/had a lot of questions.
i've tried to cover all the "fiddly suff" that no one else covers...
https://www.corvetteforum.com/forums...ddly-bits.html
i didn't shift my x-member, just used a different case mount that puts it within 3/4" of a T400.
BTO sell a new x-member with the mount in the correct position, one less headache.
yes the driveshaft needs to be shortened, but no biggie in the scheme of things.
i bought the shiftworks "shifter kit" which includes a new detent plate, but i haven't installed it yet.
reading here, you can just notch your existing plate to enable 1st gear selection, but...
i have hooked my cable up with SW bracket that mounts onto the pan and i can select ALL gears, even 1st.
as i'm downunder, i went with the 700r4 (t700 as we call them) as they came in early 90's GM Holden cars down here.
otherwise i would be up for $$$ in shipping to get a 200-4r here.
ask as many question as you need.
ps: you've got same name as well, Alan...
Last edited by riverracer au; Mar 9, 2015 at 05:30 AM.
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
I'll throw some cold water on this. If the ONLY reason to swap the trans is to improve fuel economy, consider how many miles would need to be driven to recoup the cost of the swap. JMO.
Racer
Joined: May 2014
Posts: 420
Likes: 5
From: Springfield Missouri
Good point. However, for some recouping the cost isn't a consideration. The conversion makes the car more pleasant to drive with lower RPMs at highway cruising speeds, and is easier on the wallet as you (ideally) don't have to fill up as often. It's worth the expense, even if it takes a long time to 'pay off.' This, I presume, is the mindset eurekax is approaching with.
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,559
Likes: 7,006
From: New Or-leens Loo-z-anna
Then there are members like riverracer au........it costs him nearly as much to have a transmission shipped to Australia as it does for the transmission itself! I was going to ship him a $50 trans-part....the shipping cost was $70! He has to choose his modifications carefully.
