-Flex plate / torque converter modifications
Does the stock plate need to be used in order to engage the starter? I've seen reference to modifications or a custom application. Is this just to get the stock plate to bolt up to the converter?
The key things are: The flexplate bolts to the engine crank and it's teeth must engage the starter.
The TC bolts to the flexplate.
The TC is splined and engages the input shaft of the tranny.
When you've got a combo that wasn't factory, you need to make sure that you have a flexplate that will bolt to your motor, bolt to the TC *and* make sure the TC is at the correct depth so it engages the tranny input shaft.
The easiest way is *usually* to use the stock flexplate that bolts to your motor. Hopefully, the shape of the plate is such that you can easily drill the holes needed for the TC lugs to bolt to the plate. If not, another option is to make new lugs for the converter. Drill and thread some chunks of steel, bolt to the stock TC bolt holes in your flexplate and weld the lugs to the converter. The key is to make them all consistanly the same size and weight and to uses an equal amount of welding on them. TC's are balanced and you don't want to mess that up too much. You will also need a jig to allign the TC centerline with the flexplate doing this.
While doing this, keep in mind that the TC has to sit a precise distance off the back of the motor when it's all bolted up so it's splines will engage the tranny input shaft fully, but not too far to bind. I've found you have about 3 - 5mm to play with on AW4's, the TH700 has probably a similar range.
If you're lucky, the TC will be a little too shallow and you can use small spacers on the TC lugs to space it back and make up the difference. If you're not, the TC will be too deep and you'll have to shave the TC lugs down, make new ones that are shorter, space the bellhousing back or go with a custom flexplate.
Also there may be a problem with the snout of the TC. Some TC's have a snout that extends forward and engages the pilot hole in the back of the crank. My AW4 TC does this, but the 4L60-E TC I have does not. The TH700 TC probably will not either but you might need to watch for it.
In the end, if mixing and matching parts doesn't get you close to what you need, a custom flexplate is usually the best option. You can take care of nearly all issues (depth, bolt patterns, TC snout...) with a custom flexplate.
-Torque converter
I've seen reference that the TH700R4 has a lock-up converter, and that this would somehow need to be connected to the throttle <img src="/forums/images/graemlins/confused.gif" alt="" /> (showing my ignorance). Any clarification on this would be helpfull.
Lock up is not required, but it is a good idea. You can make it manual if you like. It's activated electrically and elliminates the slip in the converter. On long hills on the highway for instance, the constant slip under load can put out a lot of heat and your tranny temp starts to spike. A locked up converter can prevent this slip/heat. It gives better compression braking down hills when locked up. Not sure on the TH700, but I think most won't lock up in 1st gear even if you trip the solenoid. Anyways, you can throw in a toggle switch and do lock-up manually.
What *does* need to be hooked up to the throttle and adjusted properly is the kick-down (or 'TV') cable. This is what tells the tranny to kick down when you floor it and it also increases line pressure with more throttle. If it's not hooked up correctly you can get excessive slip in the clutches from improper line pressure and burn the tranny up.
Will I be able to reuse the stock auto shifter?
Probably. If it's a cable shifter, it'll be a little easier to do.
--Dan
