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First off I'm new here so hey everybody. Now for the questions...I'm working on a friends 1969 427/4-speed car and he needs it converted to a automatic for his wife and I have the fun job of doing it, but have a few questions. I'm thinking the stuff I'll need is a trans/converter, cooler/lines, flexplate and shifter. Will a th350/400 bolt up to the crossmember w/o modifying it? I thought I remember reading the 350 would bolt up but wanna make sure before starting on this. I'm gonna rebuild the trans with a good kit before installing it. Also driveshaft lengths? I'm gonna assume neither auto's will work with the stock shaft? Finally the shifter....would I be better off trying to find a original one or just get aftermarket TCI/B&M etc? And does anyone make one that utilizes the stock console? Trying to make this as painless as possible. Thanks for any suggestions or anything I might be overlooking.
So your going to have to cut the crossmember out and then weld it back in in such a way to make it so it can be bolted in in the future. Other wise Your going to need to remove the Engine install the Trans then re install the engine. The Brake Master cylinder Bolts are what holds the Peddle assembly in they are not fun to get to I recommend You replace the brake booster at the same time if it has one. Why use an old 3 speed trans when everybody has been using 4 or more speed transmissions for the last 25 years. It might be easier to buy the wife a Corvette of her own.
FWIW: Purchase the 1969 assembly instruction manual (AIM) and compare the differences in the factory installations of both. The conversion you want to make is more involved than a bolt in.
Destroying a 69 Big Block 4 speed like that.
Should be punishable by death.
I'd just get a new wife.
Seriously, you stated that you wanted to make this as painless as possible. Even the tunnel is different in these cars. This WILL be painful.
Last edited by 4-vettes; Apr 10, 2020 at 08:02 AM.
You will need to cut the crossmember and flange it so it is removable.
Then remove all the pedals and corresponding pieces under there and replace with auto brake pedal......then the console pieces.
This is a JOB.
If you actually do it......put a 700r4 in it......converting this car to put in a TH400 is not good sense to begin with.......make it worth having an O/D gear.
Unless the car has sentimental value......my advice is to find someone to trade them for a 427 auto......plenty of 427 Auto owners that wish they had a 4 speed.....but not many the other way around.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
You'll have to pull the steering and dash to make getting at those pedals easier. You"ll need to make sure you find the downshift linkage as well. I would hunt around for a totalled car or someone parting out an auto car and buy everything from the pedal assembly to the tranny, but no the tranny. And buy a good OD tranny like they suggested above.
Cutting out the center of the crossmember isnt too difficult. I scribed some square lines on it and tried my best to cut it straight. Then just shave a little off the center piece so it was easy to manipulate. I used a piece of tin between the body and the frame to keep from cutting into the fiberglass floor and when I welded I used a welding blanket draped over the frame and everything I didn't want to burn or get spatter on including my QuickJack. I had an extinguisher handy and I just used a squirt bottle with straight water for any small flare ups and to cool the frame. It worked great and kept me from panicking when the welding blanket would smolder or flash.
I cant believe the difference in getting the engine in and out, so easy now
I got these from David Allvettesforme. He had a few extras back when he was doing a Restomod.
2025 c3 ('68-'73) of the Year Finalist - Unmodified
2025 C4 of the Year Finalist - Unmodified
2025 C8 Stingray of the Year Finalist - Unmodified
According to Corvette DNA app by converting to automatic the value of the car will be reduced $5000. That plus the cost of the coversion it would seem a different solution to the issue should be looked at. Maybe have wife learn stick or buy another Vette? Having said that I have done some difficult and expensive things to keep peace in my marriage over the last 42 years.
Wow! I had no idea that this was gonna be so hard to do! I had no idea about the floorpan even being different. I'm gonna have a serious discussion with him about this now. Maybe his wife will read some of these comments and say to leave it. This is not painless at all. Thanks for all the replies and I'll get back on here as soon as I find out what he wants to do.
First off I'm new here so hey everybody. Now for the questions...I'm working on a friends 1969 427/4-speed car and he needs it converted to a automatic for his wife and I have the fun job of doing it, but have a few questions. I'm thinking the stuff I'll need is a trans/converter, cooler/lines, flexplate and shifter. Will a th350/400 bolt up to the crossmember w/o modifying it? I thought I remember reading the 350 would bolt up but wanna make sure before starting on this. I'm gonna rebuild the trans with a good kit before installing it. Also driveshaft lengths? I'm gonna assume neither auto's will work with the stock shaft? Finally the shifter....would I be better off trying to find a original one or just get aftermarket TCI/B&M etc? And does anyone make one that utilizes the stock console? Trying to make this as painless as possible. Thanks for any suggestions or anything I might be overlooking.
If it’s a numbers car I would suggest you find a better candidate unless there’s a good reason. There are a lot of things your gonna have to look into. As others mentioned cutting the frame and installing a crossmember is on the list. Possible exhaust clearance issues. You already mentioned the tranny cooler stuff. As others have mentioned your gonna need an abundance of parts from either a catalog or a donor car to pull this off. Everything from the pedals to the floor shifter and all the associated parts. You will have a small fortune in parts to convert this if you don’t have a suitable donor car.
If there is a good reason to convert it IE family heirloom or something along those lines then OK. But if it’s just a get around town have fun car there are better platforms to start with IMO.
Well, it's not a numbers matching car, while it is a original 427 car the block was swapped out at one point for some reason. Also has a "325" trans which as far as I can find is from a 64/65 car. Still seems like a lot of work to swap it over. He's paralyzed from the waist down so he can't drive it and she can drive a stick but just wanted a auto but I'd say if he tells her how much is involved she may change her mind. It's just gonna be a once in a while driver to local car cruises and stuff like that. I'm gonna show him these replies and he'll probably change his mind about doing it.
Wow! I had no idea that this was gonna be so hard to do! I had no idea about the floorpan even being different. I'm gonna have a serious discussion with him about this now. Maybe his wife will read some of these comments and say to leave it. This is not painless at all. Thanks for all the replies and I'll get back on here as soon as I find out what he wants to do.
Welcome to the forum.
I agree with those who recommend getting an overdrive transmission if you end up converting the car. To that end, I would contact Silver Sport Transmissions. They have complete kits for converting cars to OD transmissions and they might also have some suggestions to make a manual to automatic conversion less painful. Here's a link: https://shiftsst.com/blog/post/1968-...ctfit-kit.html
I agree with those who recommend getting an overdrive transmission if you end up converting the car. To that end, I would contact Silver Sport Transmissions. They have complete kits for converting cars to OD transmissions and they might also have some suggestions to make a manual to automatic conversion less painful. Here's a link: https://shiftsst.com/blog/post/1968-...ctfit-kit.html
Good luck.
DC
I did actually mention to him about a 700r4 when this started but figured since these cars came with a 350/400 that one of those would be a bolt in swap....how wrong I was. Lesson learned for sure. Yeah, if he insists this is the way he wants to go with the car, I'm definitely gonna go with a o/d trans now.
Wow! I had no idea that this was gonna be so hard to do! I had no idea about the floorpan even being different. I'm gonna have a serious discussion with him about this now. Maybe his wife will read some of these comments and say to leave it. This is not painless at all. Thanks for all the replies and I'll get back on here as soon as I find out what he wants to do.
Yeah...it is not like a Chevelle or Nova/Camaro for sure.......everything is tight, real tight......tight to take apart, tight to install and tight after it is in.
The 700r4 is the best swap because it is much smaller overall than the TH350......but I do not see a person getting out of the swap for less than about 6k parts and labor.
I myself wouldn't touch the job for less than about $2500 labor......and even then I would have to think about it.
Yeah...it is not like a Chevelle or Nova/Camaro for sure.......everything is tight, real tight......tight to take apart, tight to install and tight after it is in.
The 700r4 is the best swap because it is much smaller overall than the TH350......but I do not see a person getting out of the swap for less than about 6k parts and labor.
I myself wouldn't touch the job for less than about $2500 labor......and even then I would have to think about it.
Jebby
Yep, I've done swaps in the other cars mentioned and thought this would be like those. lol Glad I came here before attempting it! You guy's are life savers!
It should fit where the manual tranny is. You may even be able to use the same driveshaft. You can buy them in multiple different strength levels. Cutting the crossmember is no big deal I did it to mine and put in a Richmond 6-speed. Even the fiberglass work on the tunnel (if you need it) is not a terribly big deal.
I've been pondering a 200-R4 and I would not even bother removing the clutch pedal if I did..... just so I could swap back to manual if I wanted to.
I do my own work (if that matters to you cost-wise) but none of it really hard, Just may be expensive if you're going to pay someone to do it.
Do a forum search. There are a few folks running 200-R4s on here.
Last edited by carriljc; Apr 10, 2020 at 01:13 PM.
It should fit where the manual tranny is. You may even be able to use the same driveshaft. You can buy them in multiple different strength levels. Cutting the crossmember is no big deal I did it to mine and put in a Richmond 6-speed. Even the fiberglass work on the tunnel (if you need it) is not a terribly big deal.
I've been pondering a 200-R4 and I would not even bother removing the clutch pedal if I did..... just so I could swap back to manual if I wanted to.
I do my own work (if that matters to you cost-wise) but none of it really hard, Just may be expensive if you're going to pay someone to do it.
Do a forum search. There are a few folks running 200-R4s on here.
Thanks, gonna check into that now. If I did it, I was also planning on leaving the clutch pedal in just in case.
First off I'm new here so hey everybody. Now for the questions...I'm working on a friends 1969 427/4-speed car and he needs it converted to a automatic for his wife and I have the fun job of doing it, but have a few questions. I'm thinking the stuff I'll need is a trans/converter, cooler/lines, flexplate and shifter. Will a th350/400 bolt up to the crossmember w/o modifying it? I thought I remember reading the 350 would bolt up but wanna make sure before starting on this. I'm gonna rebuild the trans with a good kit before installing it. Also driveshaft lengths? I'm gonna assume neither auto's will work with the stock shaft? Finally the shifter....would I be better off trying to find a original one or just get aftermarket TCI/B&M etc? And does anyone make one that utilizes the stock console? Trying to make this as painless as possible. Thanks for any suggestions or anything I might be overlooking.
I would think it should be easy to find someone to trade your 4spd parts for auto parts. Remember it's your car you can do with it as you see fit.
Converting a 69 from 4-speed to automatic.
