Prepping for 700r4 goodness

[Obwonkonobe]

Well I've been floating around a trans swap, and wasn't planning on doing one for a little while longer. But when my th350 finally gave out and lost all forward gears yesterday I went ahead and pulled it out, thankfully I had reverse to get it into the garage..

Ive got a guy building a 700r4 as I type this, and hope it pick it up this weekend, I just want to go through my little checklist and make sure I have all my ducks in a row before I crawl back under the truck

So first I had a 9 inch tailhousing th350, from what I've read the 700r4 is only 5/8 of an inch shorter than this and my driveshaft should fit. What is the minimum tooth engagment I need before I need to worry about sheering the spines?

As for the torque converter the rebuilder said he's gonna give me the original one from the core, but warrantee it for a year, but I've heard about different size converters, should I be worried about the converter bolting to the flywheel?

As for the crossmember il just line it up and drill new holes, im not too concerned. The only thing that I may have trouble with is my drill bit, should a standard bit and 18v drill be able to handle the frame? Or should I hire some muscle

And for lockup I've read that I can just wire it to cut 12v when I'm on the breaks, I won't be towing with this trans so I think I'm good there.

Im paying 550 for this rebuilt trans with a 1 year warrantee on everything, any tips on basic things to check before I pay the guy would help, he said he's keeping the stock valve body but "tricking it out" with some other little things that should make it fun. Thanks! Il post more pics as stuff happens

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[1987 GMC Jimmy]

I'm going to say a few things, but I'm far and gone from a transmission guy so take it with a grain of salt. I think as long as your slip yoke is completely over the splines on the output shaft and inside the extension housing seal, you should be fine. There should be some overlap with your current setup, but I don't know exactly how much. I feel like 5/8 would be cutting it close but doable. It's been a few months since I was playing with a driveshaft, and I didn't pay attention to how much it overlapped other than it did a little. I believe that the "to engine" pattern on the flexplates changed when they made the change from two-piece to one-piece RMS, but the "to converter" pattern stayed the same. There's one thing that I can say confidently about all this. My '86 700R4 has about 261,000 miles with no rebuild including the converter, and the transmission very clearly outlived the converter because of the lockup clutch in the TC. The only thing that makes it driveable with lockup plugged in is that Shudder Fixx goo they sell at the parts store. If anyone wants to know, there's something to that stuff, but I've had to use about triple what the directions called for. I've got a new converter in a box, but that job is pretty undesirable to me, and it is working at the moment. I bought it online from Advance Auto using that discount code they parade everywhere, and it shipped for free. I believe it was $70 for a reman stock stall converter plus an $8 core fee. All in all, I think it's a gamble to depend on an old converter, but I'd say I'm on the more radical side of that argument just from what I've dealt with. Finally, I think we may have discussed this in the past, but what about factory lockup circuit? Is it gone in yours? That's the way I'd do it if it were me just so I could let it happen on it's own. $550 is a good price if the guy's good. I've been quoted $600-$800 for a bench rebuild in my neck of the woods. I'll leave the drill questions to a much more adept metallurgist.

 

[Obwonkonobe]

Finally, I think we may have discussed this in the past, but what about factory lockup circuit? Is it gone in yours?

It was a factory th350, 1978. But It has the old cruise switch that I've been eyeing, I may use that

 

[rpcraft]

If you are talking about a 2wd truck its probably a little less critical than on a 4wd but what I would do in your case is take your driveshaft, insert it into the transmission and push it all the way in until it stops and then use a sharpie to make a line on the yoke. Once you do that let it sit for a few minutes, long enough for the sharpie mark to dry, and then attempt to insert the rear of it into the pinion yoke and just get it in enough to loosely keep it in place with one strap if you can get it in. Once you do that draw another line on slip yoke at the trans. Once you are done pull it back out and measure the difference between the two. If it is more than 5/8 then I would not sweat it but if it is less than then you may need to have your driveshaft shortened.

 

[1987 GMC Jimmy]

It was a factory th350, 1978. But It has the old cruise switch that I've been eyeing, I may use that

Oh, got it. Thought it was newer for some reason. It maybe tougher to do a factory lockup circuit starting from scratch, but it can’t be that hard.

 

[yevgenievich]

Get correct tv cable bracket. Torque converter probably already a reman, which is probably why he wanted to just use it. But long term converter would be preferred ro be fresh

 

[Obwonkonobe]

Oh, got it. Thought it was newer for some reason. It maybe tougher to do a factory lockup circuit starting from scratch, but it can’t be that hard.

Ive already fixed all the other hacked wiring on the truck, Il probably just look at a factory diagram from the 80s

 

[4WDKC]

go a head and order the kit you need from here, have this system on my vette and love it.
http://www.tvmadeez.com/about.php
and this for lock up
https://www.jegs.com/p/TCI/TCI-200-4R-700R4-Universal-Lockup-Wiring-Kit/748599/10002/-1

 

[rpcraft]

Oh, got it. Thought it was newer for some reason. It maybe tougher to do a factory lockup circuit starting from scratch, but it can’t be that hard.

To be honest I would skip the factory lockup garbage and just get you one of those lockup kits. I'm sure they are on summit, amazon, jegs, and etc. It's simpler, works better, and from what I understand completely eliminates the vaccum stuff which is generally the part that malfunctions.

https://www.jegs.com/i/TCI/890/3766...J9Za5nZi5OvPweDmdUIr6BgiYE_CYnWwaAoE8EALw_wcB

 

[Obwonkonobe]

To be honest I would skip the factory lockup garbage and just get you one of those lockup kits. I'm sure they are on summit, amazon, jegs, and etc. It's simpler, works better, and from what I understand completely eliminates the vaccum stuff which is generally the part that malfunctions.

https://www.jegs.com/i/TCI/890/3766...J9Za5nZi5OvPweDmdUIr6BgiYE_CYnWwaAoE8EALw_wcB

That's what il probably go with, but Il have to wait a but until I have the cash

 

[1987 GMC Jimmy]

To be honest I would skip the factory lockup garbage and just get you one of those lockup kits. I'm sure they are on summit, amazon, jegs, and etc. It's simpler, works better, and from what I understand completely eliminates the vaccum stuff which is generally the part that malfunctions.

https://www.jegs.com/i/TCI/890/3766...J9Za5nZi5OvPweDmdUIr6BgiYE_CYnWwaAoE8EALw_wcB

Hmm, I didn’t know they made these. I’ve seen just about everyone who had after the fact lockup flipping a switch. Definitely worth exploring

 

[Obwonkonobe]

Does anyone know if a 700r4 converter will bolt to a th350 flex plate?

 

[rpcraft]

Does anyone know if a 700r4 converter will bolt to a th350 flex plate?

it should more or less be the same flex plate for every transmission up until they introduced the LS motors (not counting big block flex plates).

 

[HotRodPC]

Does anyone know if a 700r4 converter will bolt to a th350 flex plate?

Yes, Same Pattern. Usually small block flex plates are dual pattern anyway. Either for the Th350 or Th400 bolt pattern.

Then the big block plates are all 6 bolt holes or both patterns are Th400 pattern for the heavy duty 6 bolt Th400 converter. I had to get an aftermarket flex plate for my 454 to have both patterns since I have a Th350 3000 stall that I want to use on my Th400. I wanted an SFI rated flexplate anyway so it worked out well for me.

 

[Obwonkonobe]

Yes, Same Pattern. Usually small block flex plates are dual pattern anyway. Either for the Th350 or Th400 bolt pattern.

Then the big block plates are all 6 bolt holes or both patterns are Th400 pattern for the heavy duty 6 bolt Th400 converter. I had to get an aftermarket flex plate for my 454 to have both patterns since I have a Th350 3000 stall that I want to use on my Th400. I wanted an SFI rated flexplate anyway so it worked out well for me.

Thats good, I just double checked and my flex plate IS actually dual bolt pattern. Last loose end is this though. It looks like I have to move my crossmember back 3/4 inches. To avoid drilling into my frame, could I make or buy a new trans mount to the crossmember to let me use the crossmember in its stock location?