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-   -   700R4 Torque Converter Flexplate Question (http://www.hotrodders.com/forum/700r4-torque-converter-flexplate-question-134333.html)

fosterdl 02-29-2008 05:37 PM

700R4 Torque Converter Flexplate Question
 
I think I may have a problem. I am installing a "86" 700R4 tranny behind a "70" SBC 350 with a two piece seal. The engine has been completely re-built with a new Scat crank and all. I also purchased a new flex plate and B&M 2600 stall torque converter for this installation. Everything seemed fine till I installed the new high torque starter that I got on eBay from Skip White. Once the starter was installed I noticed it was almost impossible to turn the engine with the harmonic balancer bolt in order to bring it up to TDC. Upon investigation I found that the "bendix" drive was engaged in the flex plate by just a few thousandths. I attributed this to the fact that the flex plate had not been bolted to the torque converter yet. So I went ahead and installed the flex plate bolts and found that this drew the plate back away from the bendix drive. However once all the bolts were in and torqued I noticed that as I manually turned the engine, the areas between the flex plate bolts still wanted to rub on the bendix. So what I am saying is that where the bolts are, the plate clears the bendix and in between it wants to just knick the end of the drive gear. So do I have an incompatible combination (700R4 torque Converter and "old" style crank) or is the flex plate supposed to be "warped" like that? Do I need to shim the starter motor back away from the plate? I'm confused!! Sorry if I confused you, it's kind of hard to explain.

Crosley 02-29-2008 06:31 PM

Quote:

Originally Posted by fosterdl
I think I may have a problem. I am installing a "86" 700R4 tranny behind a "70" SBC 350 with a two piece seal. The engine has been completely re-built with a new Scat crank and all. I also purchased a new flex plate and B&M 2600 stall torque converter for this installation. Everything seemed fine till I installed the new high torque starter that I got on eBay from Skip White. Once the starter was installed I noticed it was almost impossible to turn the engine with the harmonic balancer bolt in order to bring it up to TDC. Upon investigation I found that the "bendix" drive was engaged in the flex plate by just a few thousandths. I attributed this to the fact that the flex plate had not been bolted to the torque converter yet. So I went ahead and installed the flex plate bolts and found that this drew the plate back away from the bendix drive. However once all the bolts were in and torqued I noticed that as I manually turned the engine, the areas between the flex plate bolts still wanted to rub on the bendix. So what I am saying is that where the bolts are, the plate clears the bendix and in between it wants to just knick the end of the drive gear. So do I have an incompatible combination (700R4 torque Converter and "old" style crank) or is the flex plate supposed to be "warped" like that? Do I need to shim the starter motor back away from the plate? I'm confused!! Sorry if I confused you, it's kind of hard to explain.


early crank shaft and the converter are fully compatible. 700 type of trans was released in early 1980's


Is the flex plate on backwards?

Was the end of the crank shaft clean where the converter alignment hub slides in?

Was there a manual trans bushing in the end of the crank shaft?

:cool:

NEW INTERIORS 02-29-2008 08:30 PM

I have to agree,If there is a bushing in the end of the crank shaft It's not going to work. :nono:

fosterdl 03-01-2008 06:25 AM

700R4 Torque Converter Flexplate Question
 
Good thoughts and at first I thought that the plate MIGHT have been on backward, but I've checked it against a 305 I just removed and it looks OK. The crank is a NEW Scat and I'm almost positive that there is no bushing as I came sealed in the box from the supplier. Again as to the cleanliness of the crank, it is brand new. I suppose there is a possibility that the converter had a burr on it as these are all rebuilt items, but I'd hope that B&M would check that out first. At any rate if any of the above situations existed all that would do id to help straighten the flex plate and it would still be bumping the bendix. After posting I found a post from back a while and some responder recommended installing three washers between the converter mounting tabs and the flex plate to allow the converter to engage the front pump drive further and prevent damaging it, but that too would not solve the starter problem. Supposedly there needs to be a spacer there to set the converter back, but I've never fond one on a factory install. Maybe it's time for a tear down?

speedydeedy 03-01-2008 06:54 AM

If the converter is not fitting all the way into the crank this would pull the flex plate away from the starter drive gear.So it has to be something else.Is the flex plate new? I don't remember the exact years but at one time GM had a run of flex plates that where out of round.Sorry, after posting I re read and noticed your flex plate is new. Maybe it is defective.

fosterdl 03-01-2008 07:34 AM

700R4 Torque Converter Flexplate Question
 
It's starting to sound like I may have more than one issue here. One, that the converter isn't going into the crank far enough and two, the starter isn't lining up correctly.

barnym17 03-02-2008 06:10 AM

were you able to spin the convertor in the trans or did it bind on the flexplate before you bolted it up? If you could spin it that eliminates the convertor causing the starter problem.Would have to be flexplate or starter issue.As to the spacers I used them on my boys v8 s10 with a 700r4 after reading about it here worked great just used a couple washers between the convertor and plate.

fosterdl 03-02-2008 08:47 AM

700R4 Torque Converter Flexplate Question
 
The converter spun well on the input shaft before we installed the tranny, and also spun OK before I moved it forward to line up the centering hub to the back of the crank. I have a feeling that the hub isn't going all the way into the crank for what ever reason, but I suspect the the paint applied by B&M may be the cause. Once the hub engages the crank I think the "warped" flex plate problem will be solved. I was on Powermaster's (starter) site last night and they offer a shim to set the starter further away from the ring gear. I just don't know where to lay my hands on one of those.

fosterdl 03-23-2008 12:03 PM

Follow-up on 700R4 converter/flexplate problem
 
I read with interest all the replies to my question, and decided that shimming the converter back with washers was out of the question. This solution still wouldn't solve my starter engagement issue and in fact might make it worse. I jumped over to Summit and looked at all the starters and found that some starters have shims that would move the bendix further away from the flexplate, but I couldn't find any shims for my starter. As I looked around the site I ran across .030 Flywheel shims supplied by TCI that are intended to mount between the flange on the back of the crankshaft and the flywheel or flexplate. Now, I knew these were available since I remembered (after finding them) installing them when I worked as a mechanic. I ordered all that Summit had and then jumped over to Jegs and ordered 6 more. I just got done with the adjustments and using 5x.030 shims did the trick. That brought the flexplate back far enough to allow the torque converter bolts to install through the flexplate without any warpage and also gave me the desired bendix/flexplate clearance I needed. Thanks for all your replies. They were a big help.


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