4R70W Torque Converter Question

[chris]

I have a guy building a 4R70W for my 97ish (P Head Explorer Motor) 5.0 with 35inch tires and 4.56 gears. He asked which flexplate I was planning on using and I told him the one I have is a 50oz plate with 11 5/16 across the TQ bolt holes. He is saying that I should be using a smaller TQ with a 10 5/8" measurement across the flexplate TQ holes. He said he feels that with the larger TQ I will have to spin the motor up more to start moving and the smaller TQ would be better to use with the gear/tire setup I have.

I have no idea what to tell him at this point.

 

[904Bronco]

Dirtdonk has my 68 with a 98 Explorer motor, 31", and 4:56 gears. Factory flex plate and factory replacement TQ.
You can ask him, but the thing launched from a dead stop like nobody's business, kind of topped out about 75 mph though. My suggestion is stay with factory size.

 

[DirtDonk]

Stock is beautiful with the 4R70W. But 35 inch tires are big so that does change the equation. I think your gearing is perfect for general use, so my thinking is that, like 904 said, a stock converter is still the way to go.

From what you are saying I’m not sure both of you were measuring the bolt pattern the same way. Maybe double check with him, unless you already did?
Basically he’s talking about torque converter size being based on bolt pattern size, and it doesn’t really work that way. At least not every time.
Larger torque converters have a lower stall speed. And smaller torque converter‘s have a higher stall speed. At least that’s how I remember it.
So here again, make sure you are hearing him correctly.

I keep going back-and-forth between my answer and your post just to make sure I’m reading it correctly. So maybe it’s me that’s off-center and skewed. So take that into account as well!

And as far as I know there was only one bolt pattern for an explorer flex plate so make sure you guys are both on the same page when it comes to measuring. His numbers don’t sound out of line for the bolt pattern, but I don’t remember exact numbers off the top of my head anyway so best to compare your measurements again.
I suppose you could always find a different flex plate with the 50 ounce imbalance and 164 teeth. But I don’t think you have to.

There should only be one torque converter style from the factory as well, so any changes to stall speed might change the diameter of the converter but not the bolt pattern.
They don’t usually change the bolt pattern based on the size of the torque converter. At least not every time. And it was my understanding that a smaller torque converter has a higher stall speed and a larger diameter torque converter has a lower stall speed.
So your tranny guy either said it backwards, or you heard it backwards. or I’m reading your post backwards.
Are you sure you heard him correctly regarding the larger diameter being a higher stall speed?

My stock one is wonderful but it’s not necessarily a good comparison because of my much smaller tires.

 

[nvrstuk]

...what Paul said.

Go stock with that size engine and assumed EB use.

Not building a stoplight to stoplight warrior.

 

[chris]

Stock is beautiful with the 4R70W. But 35 inch tires are big so that does change the equation. I think your gearing is perfect for general use, so my thinking is that, like 904 said, a stock converter is still the way to go.

From what you are saying I’m not sure both of you were measuring the bolt pattern the same way. Maybe double check with him, unless you already did?
Basically he’s talking about torque converter size being based on bolt pattern size, and it doesn’t really work that way. At least not every time.
Larger torque converters have a lower stall speed. And smaller torque converter‘s have a higher stall speed. At least that’s how I remember it.
So here again, make sure you are hearing him correctly.

I keep going back-and-forth between my answer and your post just to make sure I’m reading it correctly. So maybe it’s me that’s off-center and skewed. So take that into account as well!

And as far as I know there was only one bolt pattern for an explorer flex plate so make sure you guys are both on the same page when it comes to measuring. His numbers don’t sound out of line for the bolt pattern, but I don’t remember exact numbers off the top of my head anyway so best to compare your measurements again.
I suppose you could always find a different flex plate with the 50 ounce imbalance and 164 teeth. But I don’t think you have to.

There should only be one torque converter style from the factory as well, so any changes to stall speed might change the diameter of the converter but not the bolt pattern.
They don’t usually change the bolt pattern based on the size of the torque converter. At least not every time. And it was my understanding that a smaller torque converter has a higher stall speed and a larger diameter torque converter has a lower stall speed.
So your tranny guy either said it backwards, or you heard it backwards. or I’m reading your post backwards.
Are you sure you heard him correctly regarding the larger diameter being a higher stall speed?

My stock one is wonderful but it’s not necessarily a good comparison because of my much smaller tires.

The Trans guy is from NJ so I may not have heard him right......

He said there was a smaller TQ and a Big TQ, we started by measuring across the flexplate and came up with two different readings. Now he did mention something about a Crown Vic 4.6 Converter. I panicked for a moment and said "you do have a case for a 5.0, right" he says yes. He may be thinking about a TQ for the Crown Vic. He says he has both there. I am bringing a spacer plate with me when I pick this up to make sure those holes match just to be sure.

I'm thinking why wouldn't I use the regular TQ from the explorer? The wheels are bigger but the axle ratio evens that back out.

 

[Broncobowsher]

Just use the stock Explorer torque convertor. It will work well for your application.