Author Topic: Swap out my 2WD TH350 for a 2WD TH700. What do I need?  (Read 13789 times)

Offline Ziptar

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Swap out my 2WD TH350 for a 2WD TH700. What do I need?
« on: September 13, 2005, 10:13:00 AM »
[EDIT] OK so I went to drive it it drives nice but now it's a TH700...... What to do??[/EDIT]

I still haven't done anything about the blown TH350 in my 85 C10 yet.

I was passing the local scrapper this morning and they had just brought in a really rusty 81-87 C20.

I was still on the rollbed and from the looks of the pan it has a TH400 in it.

Yard guy said he drove it when he picked it up, drove good, and I could come back and drive it when they got it off the roll bed. He gave me a price of $100 for the tranny and everything I would need to swap it into my truck if I wanted to come down and pull it myself.

I am thinking I will need the transmission cross member, and driveshaft (both trucks are long beds.), associated bolts and maybe the tranny lines.

Anything else I should grab while pulling it? do the Kickdown cables all hook up the same?
Thanks

Edited by: Ziptar at: 9/17/05 9:10 am

Offline roundedline

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Re: Swap out my 2WD TH350 for a 2WD TH400. What do I need?
« Reply #1 on: September 13, 2005, 12:27:00 PM »
Personally if he said you could have everything, I would get everything from the torque converter back to the driveshaft and anything else that was bolted or connected to it.  Tranny lines, crossmember (don't need it, but...) tranny mount shifter linkage etc.  The TH400 has an electrical kickdown, so you need the wiring for that...

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project


Offline Ziptar

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Re: Swap out my 2WD TH350 for a 2WD TH400. What do I need?
« Reply #2 on: September 13, 2005, 07:38:00 PM »
Good Idea Roundedline. I'll get everything I can, I'd like to have the whole truck so I could swap my body onto teh C20 frame and suspension...

I got to thinking today thought, the C20 probably has a 14 bolt rear end, my c10 probably has a 10 bolt.

The yoke on the rear end will probably be different. Anyone know if the flanges on the drive shafts are the same??

I guess I have to measure it when I go by to test drive it.


Offline roundedline

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Re: Swap out my 2WD TH350 for a 2WD TH400. What do I need?
« Reply #3 on: September 14, 2005, 09:34:00 AM »
The C20 will definitely have a 14bolt.  The input yoke on the driveshaft WILL be different and will the 14B vs 10B

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project


Offline Ziptar

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Re: Swap out my 2WD TH350 for a 2WD TH400. What do I need?
« Reply #4 on: September 14, 2005, 07:52:00 PM »
this is a family oriented site, no vugarity please -roundedline
Thought that might be the case.. I was looking up driveshafts on car-parts.com trying to figure this out.

There was only on one piece driveshaft listed for an 85 C10 and some of the shafts available had TH400 in the description. What are the chances my single piece driveshaft will work on the TH400? is teh output shaft the same on the TH400 as it is on the TH350??

The deal is so cheap I would like to make a go of it but, I don't want to get into spending 3 weeks chasing down a drive shaft or having one made up.

I suppose I could get the rear section of a piece out of a C10 and make that work but, again more $$$ and time.

Edited by: roundedline at: 9/15/05 11:18 am

Offline roundedline

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Re: Swap out my 2WD TH350 for a 2WD TH400. What do I need?
« Reply #5 on: September 15, 2005, 11:22:00 AM »
As state above, the input shaft of the TH350 and TH400 are different.  AND the TH400 is longer than the TH350.  Either way you will probably need a driveshaft.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project


Offline Ziptar

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Re: Swap out my 2WD TH350 for a 2WD TH400. What do I need?
« Reply #6 on: September 16, 2005, 04:14:00 AM »
I think I am covered.
I spoke to a driveshaft shop yesterday and explained the situation. The gentlemen there was very helpful and told me to  get the TH400 put in and get the front half of the drive shaft installed, take a measurement from the front half down to the flange on the rear end. He said to bring the measurement and my drive shafts down and he would get them converted over for $35.00.

So a little more time and $$ involved but not allot so, it looks like I'll be pulling the TH400 out of the C20 on Saturday.

I'll keep you posted.


Offline Ziptar

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Re: Swap out my 2WD TH350 for a 2WD 700R4. What do I need?
« Reply #7 on: September 17, 2005, 10:56:00 AM »
OK So I went down to drive the C20 this morning... Turns out it's a 700R4..... Square Pan and [D] on the shift indicator were my first clues...

The C20 is 85. When I check car-parts.com they list two 700R4's for an 85 C20 "4x2, 700R4, gasoline, non-ECM equipped" and 4x2, 700R4, gasoline, ECM equipped".

As far as I can tell I from looking it over it's not ECM controlled. Looks to be plain old 4BBL Carb'ed. In fact someone scribbled in magic marker on the emissions tag "84 Malibu" and the engine (305) does look to have been swapped out at some point.

According to This page at transmission center.net I found out this much...

Swap a 350 transmission to a 700R4 transmission:
If you have a 350 transmission now with a nine inch tail the drive shaft will not need to be cut. (my truck has a 9" tail)
The drive shaft yoke is the same on both transmissions.
The cross member will need to be moved two or three inches.
The passing gear cable bracket on the motor can be reused.
The passing gear cable connection on the carburetor can be reused, if you have the original carburetor.
You will need a new 700R4 throttle valve cable and dip stick.
The shift linkage can be reused. D will be OD, 2 will be D and 2nd and 1st will be to the left and right of the 1.
The 350 vacuum line will need to be removed. The 700R4 transmission doesn't need vacuum.
The cooling line positions stay the same. The auxiliary cooler always goes in the top return line on a 700R4 transmission.
you want the torque converter to lock-up you must install a lock-up kit in the transmission pan. On 1982, 1983 and early 1984's with a 27 spline input shaft you must install a lock-up kit or the transmission may burn up. Our part #12.

Turned out that my wife had to work this morning so I didn't have time to pull the trans from the C20 anyway. The Yard is holding it for me until I can get back to do it maybe today.

So this kind of changes things a bit, instead of a swapping a TH400, looks like the 700R4 will be an eaiser swap, I have a 9" tailshaft TH350 so the drive shaft works without cutting and, the #12 700R4 forth gear torque converter lock-up switch from transmission center is $45.

So the cost is still the same basically, here is the question.. I have driven it and it's a good runner however I have heard that the 700R4 is a horrible transmission, but considering my TH350 is fried and the 700R4 isn't.... I would say it's less horriblw than what I have. It'll need a front seal though, has a small drip.

Do I even want to go down this road??

The trip wasn't a total loss, they got an 83 Short bed in yesterday, Tranny is there but motor was yanked. it is a TH350 but its completely wet with trans fluid so I am going to stay away from that one I think. It did have a set of 5 lug wide rally wheels with basically new 30 x 9.50 x 15 tires on it, I got the set for $40.

Edited by: Ziptar at: 9/17/05 9:58 am

Offline roundedline

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Re: Swap out my 2WD TH350 for a 2WD 700R4. What do I need?
« Reply #8 on: September 19, 2005, 08:59:00 AM »
If your current tranny is shot, it has to be better.  The 82-87 700R4's had problems from the factory.  By 88 they had them corrected.  If the '85 has been rebuilt it could have had the updates added if the shop rebuilding it was competent.  

ECM vs. Non ECM 700R4 there is no difference.  The ECM controls nothing on the 700R4.

For the lockup switch, check this first:
www.73-87.com/7387garage/...lockup.htm

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project


Offline Ziptar

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Re: Swap out my 2WD TH350 for a 2WD 700R4. What do I need?
« Reply #9 on: September 19, 2005, 01:44:00 PM »
That's what I was thinking, looks like I'll give a $100 700R4 a shot. be nice just to have it driving again that's for sure.

Thanks for the link that's great, things make allot more sense now.

As I read it though, I realized that The TH350 I have now is a TH350C and has a lockup convertor, so I probaly have everything I need in place to do a lock up. The plug might be different though, but i have a TH350C I know for sure.

I am either going to go fetch the 700R4 Saturday or a day this week if I can get a day off from work.

I'll keep you posted as I go along.

Edited by: Ziptar at: 9/19/05 12:45 pm

Offline cooltoolguy

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Re: Swap out my 2WD TH350 for a 2WD 700R4. What do I need?
« Reply #10 on: September 22, 2005, 05:44:00 AM »
that swap is pretty straight forward, i did it in my 86 when the th350c died.  only thing u might need to do is check the rears and speedo gears, the truck with the 700r4 my have a 3:08, 3:43 or similair where as yours may have,(as well as mine)  a 2:73.  my speedo is off 10 mph now, checked with a k55 radar.  good luck with the swap just get a lot of bandaids you'll need'em


Offline Ziptar

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Re: Swap out my 2WD TH350 for a 2WD 700R4. What do I need?
« Reply #11 on: September 24, 2005, 07:50:00 AM »
Good to know cool tool guy, When you swaped did the plug for the lockup wind up being the same for the 700R4 and the TH350C??

I got the 700R4 out and home yesterday.

Removal wound up sucking completely... I am already well into a box of bandaids

The bolts for the driveshaft mounts and tranny cross member were rusted solid. Breaker Bar and impact wrench = no joy.

I took all but the two bottom tranny bolts out, I cut and crimped the lines, disconnected linkage, cut the lock lockup wiring way up on the harness,  cut the spedo cable about half way up, etc. The yard dude picked up the whole truck with the loader and dropped it on a rack. He torched the driveshaft, crossmember, and exhaust. I unbolted the TC and last two bolts and he set the truck on the ground and out it came.
I have to hand it to the yard dude though, he did a good job with the loader, didn't screw up the tranny or pan. He did bend the rear drive shaft but it appears the tranny didn't suffer from having any weight on it. The slip joint on the two piece drive line slid about about an inch so I think that saved it.

So wound up coming home with just the tranny, dipstick tube and flywheel cover but, it should be all I need.

Tranny appears to have survived the rough handling. If I put it in gear and spin the TC by hand with the tranny sitting on the floor the driveshaft still spins so.. we shall see.

Only thing that wound up getting a little boggered was the plastic connector for the TV Cable for connecting to the carb. Looks like it might still work but if I have to replace it how tough is that. I know it needs to be adjusted just so.

I need to buy / rent a tranny jack. I'll put in new front, rear seals, and a filter kit. I'll install it in a couple of weeks and cross my fingers.

Edited by: Ziptar at: 9/24/05 7:02 am

Offline cooltoolguy

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Re: Swap out my 2WD TH350 for a 2WD 700R4. What do I need?
« Reply #12 on: September 24, 2005, 01:31:00 PM »
there are two connectors, one will fit right in the other i just taped up.  as far as the TV cable goes there is one screw which holds the plastic piece to the trans,  remove the screw and pull the piece out , you'll see a hook,  unhook and replace with new cable if needed.  also it takes around 12 quarts of fluid in the 700r4, goodluck  steve


Offline Ziptar

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Re: Swap out my 2WD TH350 for a 2WD 700R4. What do I need?
« Reply #13 on: January 16, 2006, 12:05:00 PM »
I have the 700R4 in Finally. I am hoping to finish it up today and get the new holes for the crossmember drilled in the frame.

There is a vaccum or pressure switch on the old TH350 on the right side of the tranny. (see picture) Do I need to put the on the 700R4?? It has two wires leading up to the engine wiring harness. What is it??



Thanks.

Edited by: Ziptar at: 1/16/06 6:06 pm