Morning all,

I am building an ultra4 car in the UK with an LQ9 and a TH400, using a 9" torque converter, not sure of the make unfortunaly

I am having set up issues so let me run through what I have done so far....

Firstly noticed on my flex plate no holes line up which isnt ideal, i guess its because its a smaller converter than usual.

I noticed the original holes were on a part of the plate that was pressed out towards box but they didnt have a big area for new converter feet so i drilled some new ones in a more suitable part of the plate.

Both engine and box are on the bench next to each other so I slid the converter right into the box ensuring it was full engaged.

Then slid box to engine and bolted up. I then had approx 1/4" gap which I thought was a bit much but then told by my trans supplier that that was OK and not to use spacers.

I then noticed when the converter was fully into the flex plate/crank spigot there was still a gap between the torque converter tabs and flex plate. This gap disappeared if I rotated the plate to the original mounting holes where the flex plate is pressed out. So i then slotted those holes carefully and bolted it up there!

I then pulled off the box and set my dti up on the block and the needle on the torque converter shaft just behind the pump drive cut outs. I then found over 1mm of run out which i think is way too much and will cause damage. I tried different rotations but nothing seemed to change.

I then went back to my mounting holes in the fresh bit of flex plate and used 2 washers on each mount to space it correctly. Got the dti out again and found 0.5mm of run out. Getting closer! But still not perfect!

So i then tried a few different rotation positions to see if that changed anything.... no, but i havent tried them all as I havent got all week!

So then I found which mount tab was causing the problem the most. I then played around with feeler guages and found than when I put 0.35mm of feeler guage inbetween the washers and the converter tab I got the run out on the dti to 0.2mm.

So do I make up odd sized spacers to replace the washers? Or do i keep looking to find the problem. I did think about sticking the flex plate and converter separatley in the lathe and using the dti to check them individually.

Or am I being to fussy, the flex plate is called a 'flex' plate for a reason I guess!

Any help or advice appreciated

 

Hmmm. Where should we start... The flex plate you have appears to be the stock lq4 with the 6 bolt 11.5" bolt circle. A standard th400 converter would have this pattern, but it appears you have the th350 10.75" or the LS 11.06" pattern hence the necessary drilling. The converter is supposed to mount to the pressed out portion of the flex plate. You should shoot for a clearance here of .125" or about 3.2 mm. It's not common to drill the low portion and run spacers, but I suppose you could do it this way assuming you have decent engagement in the crankshaft. I would not worry about the runout mounted to the stamped flex plate. You would need a machined surface to properly check converter runout in my opinion. Hopefully this helped some.

-Brian