TH350 or TH400?

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08-29-2010, 12:51 PM
L&M

TH350 or TH400?

First, heres the rundown on my truck

94 RCSB 1500
5.7 TBI
2wd
early 4L60E

My 4L60E is starting to crap out on me, so its time to think into the future.Im going to be starting my 400sbc build very soon, so the truck will be carb'd before the end of the year.Ive been looking at swapping to either a th350 or th400.Id like to keep the truck simple and somewhat cheap to build, so the 4L60 will be ditched.My build should be shooting for around 450hp, which trans would tackle the job easier/cheaper? Ive also searched and i cant seem to find a direct answer on what is needed for the swap.Im looking for the bare-bones list, no speedo needed for now (i plan on running autometer gauges down the road).Ive read that the stock driveshaft should work just fine, but will i have any drivability prolems since the ECU wont be reading from the trans anymore? Id like to prep the trans, and toss it in on a weekend, with no surprises since this is my daily driver.Thanks in advance with any help!
08-29-2010, 12:59 PM
Frenchy

TH400 and never worry about. And just a heads up, you're gonna catch hell for not putting an LS motor in it.
08-29-2010, 01:06 PM
L&M

My assumption is that i will need the TH400/converter/flexplate/trans mount/shifter and cable....anything im missing? Which length tailhousing will i need to find to use my stock driveshaft?
08-29-2010, 03:34 PM
IXLR8

It would be hard to give up the 4-speed w/overdrive and lockup converter of the 4L60e. If the truck will see much time at highway speed a swap to a T-350/T-400 would cost you in gas mileage and longevity of the motor in the long run.

Have you considered rebuilding the 4L60e or moving up to a 4L80e?
08-29-2010, 03:43 PM
DBRODS

With only 450hp just rebuild the 60 and enjoy it.
08-29-2010, 04:52 PM
L&M

The truck RARELY sees the highway or anything over 60mph.Im ditching the 4L60E, i now have a TH350 in the back of my truck ready to throw in.I measured the tailshaft and its the 9" tailhousing.It looks to be about 1" longer than my 4L60, so the driveshaft should work just fine.My main concern now, is possible driveability problems by having the harness unplugged for the VSS and trans controls.Obvioulsy the speedo wont work, but is there anythign else that might be affected?
08-29-2010, 05:00 PM
PitchBlackC3

Since you are going to a carb, I would go with a 700r4. You will hate a non-overdrive trans.
08-29-2010, 05:13 PM
L&M

Both my 73 malibu, and my 75 nova had TH350s in them and it didnt bother me one bit.My main goal is to have a decent trans for as cheap as possible.The 4L60 isnt going to be relatively cheap to build, and in the end ill still have to mount the TPS on the motor to run it carb.Id much rather cut the bullshit and just run whats simple and effective.I know the overdrive would be nice, but its not nessecary and wont be missed.
08-29-2010, 05:25 PM
IXLR8

Quote:

Originally Posted by L&M

...I measured the tailshaft and its the 9" tailhousing.It looks to be about 1" longer than my 4L60, so the driveshaft should work just fine...

With the vehicle at ride height you should have 3/4" to 1" of play before the transmission yolk bottoms out in the transmission. If your new trans is longer you may not have enough play with it installed.