Do you have to regear the tranny when going from a 305 to a 383?

[PlayingWithTBI]

383- bore 4.005, stroke 3.800

Yes, that is one way, the other is 4.030" bore and 3.75" (like a 400 crank) stroke. In the case of Blue Print new blocks are 377 Cu in - 4.000" X 3.75"

 

[TylerZ281500]

guys........this thread hurts my noggin

350 4" bore 3.48 stroke
305 3.736" bore 3.48 stroke

cranks are the same stroke.

overbore takes you to 355 and 310ish respectively. but ultimately at this small displacement who cares, it likely doesnt have the head or management system to care.

now i lue of that. did you swap to a 350 block then? or did you keep the 305. crank is irrelevant.

do you need to regear? nope. think of regear as something that needs to happen after the transmission in relation to final gearing (IE aggressively bigger tire size) i say this because you arent drag racing and you havent upped cubes or power by a ton to warrant change for driving mannerisms. As stated 700/60e/70e all have almost the same gear patterns.

there i beat the dead horse i still wanna be less confused about this displacement thing though.

In short i wouldnt worry about the trans but if you wanna do anything id be starting with a fresh rebuild and upgrades but thats a different story.

 

[Schurkey]

hey guys, doing a swap from a 305 to a 350,

Seems straightforward enough.

it’s a .30 overbore with upgraded internals so technically a 383.

So it could have a 3.75 stroke crank, and therefore could be a 383.

383- bore 4.005, stroke 3.800

The GM "crate engine" 383 is built that way--or close. I thought the GM crate engines had the standard "4-inch" bore. Someone at GM apparently thinks "383" is magic. They're trying to capitalize on the aftermarket 383 mystique. The aftermarket 383s started out as a "cleaned-up" (.030-over) 350 block, with a cut-down 400 crank crammed into it. Then the aftermarket started building new 400-stroke cranks that already had the 350 main journal size.

now i lue of that. did you swap to a 350 block then?

That's the way I understand it. Remove 305, install .030-over 350 with "upgraded internals" which could mean 3.75-stroke crank...but apparently doesn't.

As stated 700/60e/70e all have almost the same gear patterns.

Gear pattern is the same. OD, 3, 2, 1 on the shift indicator. Even if they're labeled OD, D, 2, 1, you're getting the same ratios.

Gear RATIO is also the same. If 2nd gear ratio is different on some transmissions, I don't know about it.

Actual gear part numbers can be different, because the 700/4L60/4L60E/4L65E/4L70E has been updated so many times that it's hard to keep track of them all. The bigger differences is in the number of planet gears--most have four planets, some have five.

But number of planets doesn't change the ratio. Just the strength/torque capacity.

 

[Jimbo2312]

Thank you big time guys. I am fascinated on transmissions and why it’s the last thing anyone ever talks about.. anyways, to clarify: truck ECM is stock with a 305. I swapped to a 350 after my motor started knocking. Was over bored 30 and verified it has a 350 crank, not a chopped 400 crank. I need an itemized copy of this build because I don’t trust this guy all that much. Thank you very much for your help, I drop it in Monday- Wednesday

 

[Erik the Awful]

I am fascinated on transmissions and why it’s the last thing anyone ever talks about.

They're difficult to work on, and even if you're a perfectionist, you're likely to have issues. Porous cases, fragile planetaries, and bad tech data are common. Not to mention it's at least four hours of labor to swap them out in your driveway. Then you need specialized tools and a full week to rebuild one. Never mind that there's no "everything you need master rebuild kit". There are so many parts that have to be bought individually, but you don't know if you need them until you inspect them, and that leads to a week of downtime while you wait for parts to arrive. That's the struggles before you find out if you have the temperament and patience to put it back together without nicking a seal, without getting a lip seal backwards, without forgetting where your check balls go, and with trying to get your teflon seals to shrink down long enough to get them into place.

Transmissions suck, and once you learn the ins and outs of rebuilding one, the manufacturers come out with a new one that's even more finicky and fragile to rebuild.

 

[Pro439]

Myself personally I wouldn’t try to use a 4l60e it just doesn’t look strong enough internally with that being said to use a 4l80e you would need different programming and with the exception of the electronics,valve body and OD unit the rest looks like a th400. If you used 1 of those and the pan was fairly clean inside (you will have a black coating inside the pan) no pieces in the pan then I would recommend putting a transgo hd2 shift kit in it and replace the electrical parts and giver hell. As far as gearing goes there are several sites you can look them up on. 1st is like 2.48 , 2 a 1.98 , 3 is 1 to 1 and OD .78. That doesn’t change until you go to the 6 speed and then 6 th is still.78 they just split it up more so the engine doesn’t rev up so much to shift and they are geared more to shift w/o noticing it shifting. You need to have good pump pressure 250 -300 psi. 2 places that you can get parts from are Jakes Performance and PATC. To answer your other question about what you have for an engine a 350/5.7 is a 3.48 stroke or just shy of 3 1/2” inches. A 383 is a 3 3/4” inches. The bore is on a 350/5.7 is 4” inches and the 1st over bore is.030 over which is hard to see on a ruler but would be just over 4” inches but not 4 1/16” inch a 305 has the same stroke as a 350/5.7 but much smaller bore and really wasn’t a good engine combination. The other thing you have to remember is the rod ratio. A stock 350/5.7 block you can only use so much rod because the deck height is too short

 

[Schurkey]

truck ECM is stock with a 305. I swapped to a 350 after my motor started knocking.

You're gonna need to change the PROM or Calpack or whatever so that it throws enough fuel for the added displacement.

Or just change the entire computer for one that came with a 350.

 

[TylerZ281500]

what year is this thing? likely need some tuning on the fueling tables for difference of displacement. depending on year could mean vortec or tbi which are tuned differently.

 

[Jimbo2312]

Black bear is a company out of northern Idaho that remaps the computer in the k1500 for $325, I could go to a pick and pull but I think it might save some headache to buy it from them

 

[TylerZ281500]

0411 swap and tune on the fly with hpt or ls drois etc = free