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Old 03-25-2015, 03:31 PM   #12 (permalink)
oil pan 4
EV convert
 
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Join Date: Jul 2011
Location: NewMexico (USA)
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Sub - '84 Chevy Diesel Suburban C10
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Quote:
Originally Posted by cosmick View Post
a 6.2L diesel only makes a truly lame 240 ft/lbs TQ, no more than an equally lame 305 gasser. The 6.2 feels torquier to drive than the 305, but that's only because the torque comes on quicker and stronger off idle.
A 700R-4 does need to be "built" to survive a 6.2, but even stock 305s break the best of stock 700R-4s, however, the 700R-4 isn't inherently weak, most of the guts are as strong as TH400 guts.
I don't have a 6.2.
I have a 6.5L block, with 6.2L heads then that is twin turboed and intercooled.
Then while the diesel engine is out I am putting a waste gate on and I may put a the bigger new injector pump on along with new injectors. The injector pump has a lot of miles on it and I believe the injectors leak a little.

The Th400 has 3 major design flaws as far as I am concerned, it has no over drive and no torque converter lock up. There are after market options to put a locking torque converter on a TH400 but, but its still missing a gear.
Then the first gear in a TH400 is about 2.5:1 where a TH700 has a 3.1:1 first gear.

Cooling the TH700 wont be a problem. I have 3 transmission coolers and 1 factory installed transmission fluid heater. As long as the torque converter lockup is working the 3 cooler are tremendous over kill. When lockup is engaged not towing anything I think it actually needs the factory transmission heater.
I have only seen it get real hot with no converter lockup while towing another car on my trailer.
I weighed the 3/4 ton suburban, with a full 40 gallon fuel tank it weighed under 5600lb. So the weight difference between the half ton and 3/4 appears to be nearly nothing, or about as little as a full versus low tank of fuel.

I am having a transmission shop near Lubbock rebuild the transmission. They are going to put in a 30 spline 5 planetary gear set, high pressure high volume hydraulic pump and upgraded higher count clutch packs and most importantly a working 30 spline lockup converter.
Sad thing is they want almost the same amount of $ to build that bullet proof 700R4 as my local transmission shop wants to do a stock rebuild. I have been told my local shop is a rip off this appears to be true.

When towing something heavy my plan is to put the shifter in 3 making it like a TH400 since they share the same 3rd gear ratio of 1:1. And because my 700R4 is an 1984 the torque converter lockup will lockup in 3rd gear. Later 700R4 transmissions will not lockup in 3rd gear unless you modify them.
Plus I added a torque converter lockup control switch. I can turn the lockup off, run it like normal or turn it on when ever I want.
__________________
1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.

Last edited by oil pan 4; 03-25-2015 at 03:36 PM..
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