Dreaming of a 700r4 for 75 150 pickup

Rusty Scout

Rusty Scout

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My 1975 pickup has a Scout II type rear tranny crossmember setup with an additional crossmember under the bellhousing whose only duty is to keep the frame rigid(this one could be modified to help support a 700r4 since there is less beef here than a 727).

With the longer tailshaft rear supported 727 and divorced NP205, a 700r4 conversion seems like its begging to be done here. Looks like there might be a heavy duty rv 30spline version of 700r4.

First question since I know very little about GM products is what's the best year/version of 700r4? Best junkyard donor truck? Maybe Jeff already has a pallet of the proper 700r4 in his warehouse?
 
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Are you prepared to spend well in excess of $2k for a properly built 700 transmission and conversion system???? You can buy one dam lot of gasoline for that kinda cash.

Let's see...payback on that at "maybe" an average fuel milage improvement (with no trailer pulling) of one mpg would be about 20 years at 10k miles a year.

A far more practical (and simple) "overdrive" setup would be the installation of a gearvendors unit in the NP205. I'll have pictures of that setup posted in the next few days I hope.
 
I was guessing the money spent would be up in the mid $3k range just for the parts alone?

Well I said dreaming didn't I. I would love to hear about the overdrive and that sounds like a real payback situation.

My original thoughts were based more on performance than payback. I want to keep my 3.54 gears but I would also like to have a lower first gear and the option of overdrive. What's the 4low ratio on the NP205? Isn't it like 1.96:1?

A lower gear set for the NP205 and an overdrive would accomplish the same goals but cost a little less.

Edit: from what I can tell from the gear vendors website is that they want $2995 for the dodge NP205 overdrive unit. These units look a tad bit long. Looks like you would need to shorten the rear drive shaft by about a foot. I still want to see your pics if you can? It is a toss up which way is better for me because I have enough low gear now to suit my needs ok.
 
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I wasn't able to get the pics of the gearvendors setup last night. When the rig showed up it had a ton of snow/ice on it and the undercarrriage was partially frozen and water pouring off. I wasn't gonna crawl underneath in the water.

We did manage to complete the carburetor and 727 kickdown adjustments, and verify that the throttle linkage that the fabricator revised last week was effective.

With a completely performance-built (no expense spared) 392 in a 5600lb. '66 t'all with 275-16 tires and geared 4.10, the rig runs 2700rpm at 75mph in od and it can be split-shifted in all gears which is a huge advantage for dragging a carhauler trailer up and down the passes. Mileage has yet to be accurately verified due to the continuous mods we've made to the carb and ignition system, but fuel economy is way down on the list of why the gearvendors unit was chosen for this application, there is no payback for any of this stuff regarding fuel costs.

The various "gear calculators out there don't mean shit in my world of ihc stuff. They do not take into consideration that any ihc-produced vehicle has the aerodynamics of two sheets of plywood, weighs at least 1,000lbs. More than any comparable vehicle, etc. Online "calculators" are fun to play with,...the real world of a near 6,000lb. Loaded vehicle, pulling a 6,000lb. Trailer up a 6% pass against a 40mph headwind in ice/snow, in low range on the 205, is something else again.

The torque converter we put in this one is a local build and extremely tight in action with a 1750rpm stall speed. It is a "built" 727 with shift reprogramming involving no electricity and no internal slippage when shifting up and no binding when shifting down. And in pulling/descending grades, the transmission is shifted manually which hugely adds to it's versatility.
 
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