TH400 to 700r4 Conversion

[veinbar]

I have a TH400 currently that needs to be rebuilt. With the suggestion of a few members I am now considering a 700r4 conversion. I drive a '79 SWB 1/2 2-wheel drive Bonanza. I know that the 700r4 will bolt up to the motor and cross member w/ no issues. The questions I do have:

1. My '400 has a 2-piece drive shaft. I will need a 1-piece for the 700r4. Does anyone know the exact length of a driveshaft on a '73-'80 truck w/ a 700r4?
2. Will the linkage have to be modified?
3. Will the direct line from the tail of the 700 to the 12 bolt be a safe/operational angle?
4. I know that the 700r4 requires additional cooling, but what else can I expect to change or modify with this conversion?
5. Do driveshafts really need to be balanced anymore? some people say yes, some say no.
6. Some 700r4 cores are better than others. Which years are the best cores to overhaul?

Other questions will pop up along the way, but this is a good start. Thank you in advance for chiming in with advice and information.

[Jonboy]

1. Not sure, but a 1 piece driveshaft from a shortbed with a long tailshaft TH350 works perfectly.

2. No. It may need to be adjusted, but it will work. You may want to find a quadrant out of a later model 700R4 equipped truck, if it matters to you.

3. Yes.

4. Not really. Heat is the enemy of any Automatic transmission, just not the 700R4. An auxillary cooler is never a bad idea (if it is installed right).

5. It can't hurt, especially if you are having one cut.

6. The really early ones had lousy pumps. Seems like 87-88 had an auxillary valve body added also.

Another note- I would look into some type of TCC engagement. Bowtie Overdrives sells a pretty nice kit for around $60, IIRC. It will include a new brake switch, too.

[VWBeamer]

Here's a curve ball, get a 4L80E. It's basically a 400 with over drive. Super strong. And I know that the electronic part sounds complicated and expensive, but stand alone controlers are 500 bucks, but consider no messing with a TV cable, special throttle hook ups and no worry about how you are going to lock the converter, it's a good deal.

http://www.optishift.com/?gclid=CMWB...FcV_5QodY0J2xg

Plus the 4l80E is TONS stronger. ...and doesn't have the huge drop off in RPm between 1st and second gear.

I know it doesn't answer your question, but you can get a transmission that is twice as strong for just a little more effort and money.

[softballnrd27]

The 4l80e is a good option but possibly overkill if you just plan to have a mild SBC. A 4l60e is the electronic version of the 700r4 so there isn't much of an upgrade from a 700 other than the electronic part, no TV cable.

[chevy-fun]

88-93 700r4 are the betters one to rebuild
Posted via Mobile Device

[veinbar]

Thank you for the rapid responses. I think 700r4 will be more than enough to handle my near stock sbc. Perhaps a few internal upgrades for added strength and reliability. What would i have to do to make a 4L60E work with my truck? It would be nice to eliminate the tv cable.

[VWBeamer]

The same controller made by optishift will work with either transmission.

To get an idea what is involved, here is the manual.

http://www.optishift.com/downloads/GMmanual.pdf

[Jonboy]

You will also have to swap th a 90-91 Electrinic cluster or use somethng like a cable-x box to make the speedometer work. That is the biggest downfall of using the 4L60E/4L80E.

[veinbar]

Originally Posted by Jonboy

You will also have to swap th a 90-91 Electrinic cluster or use somethng like a cable-x box to make the speedometer work. That is the biggest downfall of using the 4L60E/4L80E.

So perhaps it would be cheapest to run with a 700r4? I'm assuming the electronic aspect would be a bit more pricey.

Just a side question... You have a 350 TBI, 700r4 and a drop. You're probably getting some pretty decent mileage right. Do you know your hwy vs city mpg average? What rear gear are you running?

[gchemist]

My builder can probably get you in a nice 700R4 starting at $750+. Price goes up as parts are upgraded or added.

I run a 85 Camaro 700R4. The tailshaft is from a truck. Upgraded like crazy! You should go for a ride with me.

[Jonboy]

Originally Posted by veinbar

So perhaps it would be cheapest to run with a 700r4? I'm assuming the electronic aspect would be a bit more pricey.

Just a side question... You have a 350 TBI, 700r4 and a drop. You're probably getting some pretty decent mileage right. Do you know your hwy vs city mpg average? What rear gear are you running?

It's rinning a 3.73, with a 255/70 rear tire. I am still working an a few teething problems from the swap, so it is hard to tell what kind of mileage I am actually getting. I have only run a tank of old gas through so far, so it's not really fair to try to average it just yet.

[INSIDIOUS '86]

Originally Posted by chevy-fun

88-93 700r4 are the betters one to rebuild
Posted via Mobile Device

30 spline are the ones to get not specificly a certain year but 30 spline input shaft was done early-late 84 i believe?

http://www.transmissioncenter.net/ call these guys the know thier stuff and will stay on the phone with you for hours to answer any Q you have

[veinbar]

Originally Posted by gchemist

My builder can probably get you in a nice 700R4 starting at $750+. Price goes up as parts are upgraded or added.

I run a 85 Camaro 700R4. The tailshaft is from a truck. Upgraded like crazy! You should go for a ride with me.

I'd love to. I could use some input from a local classic truck guy.

[Pop's C-10]

Originally Posted by INSIDIOUS '86

30 spline are the ones to get not specificly a certain year but 30 spline input shaft was done early-late 84 i believe?

http://www.transmissioncenter.net/ call these guys the know thier stuff and will stay on the phone with you for hours to answer any Q you have

i think tha 30 spines came in about 88...

[gchemist]

GM used 27 input splines from 82-84. GM went to 30 in 85, hence my 85 Camaro 700R4. Strout motor Camaros and Vettes were stripping the input in spline. Later, aftermarket suppliers used hardened parts to make them stronger.

[gchemist]

Originally Posted by veinbar

I'd love to. I could use some input from a local classic truck guy.

Oh yea, we'll go a nice ride!!

http://www.youtube.com/user/Silverad...14/SxscAUgYLeI

[54Caddy]

I recently done this swap. All in all costed me about 1200. have a fully rebuilt trans with stage 1 shift kit and corvette servo. running a non lock up converter so no need to wire up trans. ordered a tail shaft housing cover that will make the 700r4 fir on the th400 crossmember with drilling or elongating of mounting holes. bought a driveline out of a truck with a th350 installed new ujoints and balanced it fit perfect. ordered lokar tv cable and throttle cable with bracket for edelbrock intake/carb set up. If youd like part numbers let me know.

[bradford]

Originally Posted by 54Caddy

I recently done this swap. All in all costed me about 1200. have a fully rebuilt trans with stage 1 shift kit and corvette servo. running a non lock up converter so no need to wire up trans. ordered a tail shaft housing cover that will make the 700r4 fir on the th400 crossmember with drilling or elongating of mounting holes. bought a driveline out of a truck with a th350 installed new ujoints and balanced it fit perfect. ordered lokar tv cable and throttle cable with bracket for edelbrock intake/carb set up. If youd like part numbers let me know.

I would like the part numbers please.

[gchemist]

400th to 700R4 swap info: http://transmissioncenter.net/700R4_Swap_Info.htm

700R4 tip sheet: http://www.transmissioncenter.net/700r4.htm

[INSIDIOUS '86]

those corvette servos are only like 15% more holdin power over stock with still isnt much for high torque, but a sonnax servo and some new boost valves and a lockup kit with shift kit makes a durable trans, and dont forget that beast shell! most shops put in new clutches and a shift kit with some stiffer accumulator springs and say its good. they still burn and break

[veinbar]

Originally Posted by 54Caddy

I recently done this swap. All in all costed me about 1200. have a fully rebuilt trans with stage 1 shift kit and corvette servo. running a non lock up converter so no need to wire up trans. ordered a tail shaft housing cover that will make the 700r4 fir on the th400 crossmember with drilling or elongating of mounting holes. bought a driveline out of a truck with a th350 installed new ujoints and balanced it fit perfect. ordered lokar tv cable and throttle cable with bracket for edelbrock intake/carb set up. If youd like part numbers let me know.

I would love all of those part numbers. I ran into many issues when converting my '76 g10 to a 700r4. Needless to say the transmission lasted about 12k miles before it needed a rebuild.

[veinbar]

Originally Posted by gchemist

400th to 700R4 swap info: http://transmissioncenter.net/700R4_Swap_Info.htm

700R4 tip sheet: http://www.transmissioncenter.net/700r4.htm

Thank you... These are very helpful. I'll probably never have a reason to build a 700 as stout as yours, but I will need a solid 700.

[veinbar]

Progress... Yesterday I pulled a 700r4 out of my '76 SportVan that will be going into my '79 Bonanza. It already has all of the internal upgrades I would want or need, just needs a rebuild.

[D.FENS]

Not trying to get this thread off the track, but will a 700R4 last behind a 454 in a dually? Local trans builders give conflicting answers.

[veinbar]

Originally Posted by D.FENS

Not trying to get this thread off the track, but will a 700R4 last behind a 454 in a dually? Local trans builders give conflicting answers.

I would suggest the 4L80E which is basically a TH400 transmission with overdrive. I'm sure a 700r4 can be built to handle just about anything, but it would need just about every internal heavy duty upgrade that is offered. You might want to compare the prices of both and make your decision.