Max fuel economy for the 6.5TD

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Probably have to massage the T CASE shifter too.....

The 700R converter has a smaller bolt pattern...The 4l80 has the large pattern.

Most 6.5 flex plates have 6 bolts.

Since the 6.5 never had a 700R the holes may need to be added to allow the small converter to bolt up.

Fun stuff.....

The swap from a 700 to a 350 was so popular back in the 1980's that the aftermarket made a trans/txcase adapter just for that swap, that made it really easy. The adapter allowed joining the TH350 to the original transfer case used behind the 6.2. Didn't have to change the position of the transfer case or cross-member.

Swapping to a 350 during the 1980's didn't have a lot of downsides - mostly upsides... The national speed limit, even on Interstates at that time was a snail's pace 55-mph. I swapped back to a 700 when the national 55-mph speed limit was lifted. The TH350 made the 6.2 unusable for anything other than back roads... because 70-mph meant 3000-rpm in a 4.10 geared truck. Our speed limits were even higher - they are 80-mph now. The TH700R4 had a 0.71 OD. In my 3.42 geared truck, that TH700R4 OD produced about 1800-rpm at 65-mph, which was heavenly after 200,000 miles of having no overdrive.

Another big advantage of the OD was that the diesel rattle practically disappeared at 65-mph and over. Then, there was the fuel economy advantage... I saw a change from 17 to 24-mpg during my 50-mile commute. All combined, I was very happy with the TH700R4.

Going to a 4L80-E in a non-computerized truck means buying a computer and wiring harness (about $1200) in addition to the cost of the transmission. It also means engine sensors (TPS - ESS). I installed a 4L80-E and computer and wiring harness and engine sensors in a non-computerized truck. I did it for the power handling capability.

Someday, if the DS4 or existing 4L80-E in Sarah's Blazer ever give up, I'll be highly temped to swap in a TH700R4 and mechanical DB2. There's no reason this engine can't deliver low to mid 20's in fuel economy instead of the 15-17 it does now.

There are two flexplate options for the 6.2/6.5 - "light duty" and "heavy duty". The only difference is TC bolt circle - both use 6 bolt TCs. The TH350 and TH700R4 share the same smaller bolt circle, and the TH400 and 4L80-E share the same tiny bit larger bolt circle. The difference isn't very much. From a short distance away, I doubt many could tell the difference in size between a pair of TCs or flexplates made for each transmission.

Here's a pic of Howard's 1987 1500 Suburban and his 36' Airstream... There's a TH700R4 in that Banks 6.2 powered Suburban. He was from New Jersey. That pic was taken here in western Montana.