Thread: Tranny swap

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My '73 el camino has a Turbo350 transmission with a floor shift.
I have a 700R4 Transmission which is in better shape than my T350. Plus it has an over drive gear.

I was wondering if anyone can help me out on the swap. I can't find anywhere that shows me size specifications for the two transmissions. I need to make sure the 700R4 will fit. I need to know if I can use the same crossmember or not. I also need to know if I'm going to have to cut my driveshaft a couple inches.

Also are their any suggestions for doing this?

Maybe no Chevy guys saw this. Let's give it another go round for you, as this should be a pretty common swap. Maybe someone will answer for you this time.

Don

Well I have been looking up on this a bit online and mainly what I have found is the following:
1. T350 crossmember can be used, but needs to be moved an inch or 2 (requires drilling new holes in frame
2. Driveshaft shortened (which is cheap at the local machine shop)
3. I saw a couple things about installing the lockup kit? And some vacuum lines?

Currently in the el camino my t350 doesnt drop into passing gear except manually. Which I think is because of vacuum but I am not sure.

I put a 700R 4 in my 1977 C10 truck
I moved the transmission crossmember back About 2 inches ( Iwas able to use the back frame crossmember hole for the front crossmember hole )
I had a long tail shaft 350 transmission in the truck and put a short tail shaft 700R 4 in and I was able to use my old drive line with out doing any thing to the drive line .
Look up Chevy 700R 4 on the internet and you will find some GOOD help on the lock up Plus the 4 th gear band cluch
I was told if you drive around in overdrive with out the lock up that is what causes the 700R 4 to go out , only us the overdrive above 50 MPH and use the lock up when you do
The 700R 4 have a T.P.C. where the 350 have a kick down cable ( it is VERY inportant that the T. P. C. be adjusted right or the transmission will not last long ) I had my local transmission shop adjust mine They did it fo nothing

Originally Posted by weylinthedirty

Well I have been looking up on this a bit online and mainly what I have found is the following:
1. T350 crossmember can be used, but needs to be moved an inch or 2 (requires drilling new holes in frame
2. Driveshaft shortened (which is cheap at the local machine shop)
3. I saw a couple things about installing the lockup kit? And some vacuum lines?

Currently in the el camino my t350 doesnt drop into passing gear except manually. Which I think is because of vacuum but I am not sure.

you would do away with the vac. line on the 700r4, you don't need them. sounds like the kick down cable is out of adj. on the 350. thats where you get passing gear from. with the carb. wide open there should not be any slack in the passing gear cable.

If you do the 700R4 swap you will have to get a T.V. cable bracket from a donor source. Make sure the cable is adjusted correctly or your new trans won't live long...
Mark

T.V. cable bracket? Well the Trans Am I'm taking the tranny from is also carberated (1985). I could use this one right? It has one of those stupid ass electronic quadrajets. It's stupid it pisses me off everytime I touch it.

Originally Posted by weylinthedirty

T.V. cable bracket? Well the Trans Am I'm taking the tranny from is also carberated (1985). I could use this one right?

That's perfect!

Ron Francis Wire Works has the lock up switch you need for the converter. Cost $150....... I have 2 in my street rods. One on a turbo 350C and a 700R4. Very easy hook up and I have had no problems for years. It is true that you cannot run the 700R with out locking it up unless you do some serious modifications which need to be done by professionals.

10-4 on lock-up , you will toast tranny w/o lock-up due to heat generated with t/c slipping. 31 5w

On your lock up you can take the plug off the doner car, there will be a pink or purple A term, light blue B term, tan/blk D term you will need the brake switch also the A term gets voltage from the brake switch, the D term is ground side of solinoid which can be hooked to a ground and trans will lock up in 2nd gear or you can take and hook the D term wire and the B term wire
together which is the fourth gear switch and converter will lock up in fourth.
Piece of cake and you do not even have to take the pan off.

Hi All,

I've just tried that wiring with D and B together and A to 12V brake switch and transmission locks in all gears.. , any idea what's wrong???
Thanks lot.

I guess I didn't realize the trans was a 85 because it wired different, On the A term (voltage) goes through the 3rd gear switch so you should be able to ground the D term and have it go into lockup in third gear. Iam not sure what you are refering to when you say all gears at best it should lockup in 2nd gear, can you or have you driven it since the swap? You can also check continuity
between A and D you should not have continuity until in third gear, if so it should lock up in 2nd.
Do you know if anyone has worked on this trans?
Terry

Hi ,

Sorry , in fact I'm just catching the train ... , I'm not the one that initiated the subjet but with the same problem!!! And so far you're answer is the only one simple and clear that I've found all over the net... , so in my case my car is an 85 trans-am that has seen it's LG4 swaped for old school 355 carb so the Tranny is still it's original TH700 and I need the lock=up running without the ECM , and you're the only one mentioning those wires color that I have wich are purple , blue and the third one black/tan. So I've hooked the blue and black.tan together et the purple to 12V key brake switch. Test drive is weird seems that the tranny is locking one each gear from first to OD.. , ANY IDEA WOULD BE HIGHLYYYY APPERCIATED !!
Thanks lot!!!

Since you are in Mesa you might want to talk to the Guys at Sav-On Transmission they are located 2 blocks south of Indian School on 43rd ave. they have been into Rods for years and they will give you good advice and treat you right on price,for the driveshaft call Dick's at 602-244=8115,I have had several done by him great guys to deal with.