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T-350 to a 700r4

1215 Views 6 Replies 6 Participants Last post by  Hogg
I have an 84 chevy pickup 2wd sb with a th350 and was woundering what all i would have to do to make a 700r4 out of a 86 suburban work? i have a 305 with a mild cam and 3.08 gears for now and looking for a lil more takeoff and somebetter mileage.
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trans swap

This swap should be rather easy.The 700 is a direct bolt up in place of the 350.I would use the column from the Sub so you have the correct shift indicator.You will need to hook up the TV cable to the carb and adjust correctly to get the correct shift points.I had an 84 C-10 and it had a 700r4 with a 305 and 3:08 gears.It got 18-19 mpg on the hwy.Good luck
very simple, it will practically install itself

same dirveshaft
same flexplate and starter

same shift linkage

the kickdown cable will connect the same as the TV cable did

happy swapping
1st gear acceleration will be better but 1/4 mile acceleration is better with teh thm350 trans.

3.08's with a 700r4 will make 4th gearvirtually unuseable. I suggest a 3.73 gear with the OD trans.

My dad's '94 Sub works fine with 3.08's & a 700. A hot-rod it ain't, but it runs fine on the open highway running 70-75mph in OD. If you're towing or otherwise heavily loaded, I'd recommend not using OD at all, but if you're running fairly light, it works fine.

Looks like you're not too far off the Pig Trail (Hwy. 7), so you might not get much chance to use OD, because on hills, it will want to jump in and out of OD so much it won't do you much good. Dad's prefers to be in 3rd in the East Texas hills, and the ones I remember in that part of Arkansas kinda humble those little humps.
the 700 is 3an 3/16 inches longer than the 350 also the crossmember will have to be moved back 2 in. If you can find a 700 tail shaft houseing with a boss for the tranny mount. it will line up where a 400 trans would since your frame has holes from the factory to mount the crossmember for a 350 or 400 you could use the 400 position and not drill at all. the shift linkage lines up the cooling line line up you need the tv cable and you need to power the tcc solinoid if you don't the trans will over heat in overdrive I beleive 86 was carberated so the wire harness is easy to rewire the "a" terminal on the wire conector needs 12 volts this feeds through the 4th gear switch and the solinoid groungs it self you get 4th gesr lock-up only To check if you have this wire harness drop the pan it only one wire goes to the solinoid and that wire runs thru a switch you just need to get 12 volts to the switch .
The thm 350C used in the classic body style trucks around 1984 are the same length as the thm 700r4's. The truck thm 350 also uses a lockup torque converter like the 700r4 uses, the 4 pin plug is the same on BOTh trans.


My 1997 reg cab shortbox Vortec 350 truck came stock with 3.08 gears, 27" tires and was boggy as heck on the slightest grade.
3.08's with an OD trans will suck for anything but even grade cruising.
i am running 3.42's now and they are a perfect highway gear, teh 4.10's revveda bit too much for 75 mph crusining but were awesome in town.
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