[robmobile1970]

What is the difference in size between the torque converter bolt pattern on the turbo 400 attached to the bread trucks and the standard turbo 400? I remember unbolting the turbo 400 from the engine when I got it and it had 6 bolts on the converter.(I live 3 hours from where I got the engine so I can't go back and look at it easily) a turbo 400 at my buddies house has only 3 bolt holes and they are the same size as the 700r4. I am thinking of using a chevy flexplate as a adapter bolting 3 holes to the ribbon and 3 holes to the 700r4. Now I have my ribbon slotted and am using washers to bolt up the 700r4 converter. It is still tight after about 1000 miles, but I have vibration similar to a bad universal joint at highway speed with the TC locked up. It makes me feel like with my bolt holes slotted it might be slightly off center??? causeing the vibes. Maybe the vibes are totally normal. I have no other street 4Bt vehicle nearby to ride in and compare to mine. I do know if I unlock the converter and drive the same speed the resonance goes away.

 

[Machman]

My understanding was that ALL TH400's had larger bolt circles for the torque converters (same size as the 4L80E), and that the 700R4 / 4L60E was smaller, same size as the TH350 TC..

Can you lock the TC in a gear other than 4th? If you can, try it and see if the vibration tracks with engine speed or with road speed.

 

[DarylB]

Have something machined, adding washers is not a good way to engineer something, unless you have the entire assembly balanced. Adding washers is like adding weights to the flywheel. If it's slightly out of balance you'll eventually flex/break something or always have a vibration. The TH400 has an 11.5" diameter pattern, the 700R4 has an approximate 10.5" diameter.

I think diesel durango made him ring to adapt his from the 6 to 3 pattern. I had the proper 11.5" pattern built on the 700R4 converter. Check out the thread.

 

[robmobile1970]

I will probably end up trying to get one of the 800rpm RV converters made for 6 bolt 11.5" pattern. My setup seems solid enough I just doubt it's balance. I copied what another guy did on his offroad rig. Or maybe I'll find a real good deal on a 5spd. I used to live near a U pull it junkyard in WA where all tranny's were $125 regardless of what it was.

 

[robmobile1970]

Thanks for the information on the bolt pattern. I'll see if I can find a flexplate with the 11.5 bolt holes.