Planning on swapping my 350 into my 1986 trans am 305 t5 trans. A few questions first off is it a drop in and run swap or will i have to do any modifications the engine is from a 1992 truck. do the engine and trans line up the same? Also wondering about how to build my t5 transmission to withstand my low mileage 350 mild built.

 

You can't build your T5 to withstand anything, sorry. The problem with T5's is the case flex and it stretches everything out over time from the torque. If you dont beat on the tranny at all, it'll last perfectly fine though. Dont EVER power shift the T5 and make sure you have a really good aftermarket shifter on there and dont miss 3rd gear and you'll be fine.


Your T5 tranny and bellhousing will line up perfectly fine with the 350, however you will need to purchase a new flywheel.

1986 and older SBC's (just like your 305 in your 86 T/A) are 2-piece rear main seal. 1987 and newer SBC's (like your 1992 350) is a 1-piece rear main seal. You will need to find a flywheel for a 1987-1992 305 5-speed F-Body as they are all 1-piece rear main seal 305/T5 cars.

No, you can't just use "any" flywheel, and dont waste any money trying to "beef up" your T5. That money would be better off being put towards a T56 6-speed or TKO tranny.

 

The 92 truck 350 runs a weighted flexplate. Whatever flywheel goes on has to be weighted/balanced accordingly

 

I recently pulled my 305 out of my 86' TA and put in a 383stroker ( 350 block ). Mine has a 700r4 trans but the only two things I had to change was the starter and flywheel. The starter on 305 has offset bolt holes where the starter on the 350 has bolt holes that are side by side. Obviously the main reason I had to change flywheels was due to the 400crank in my engine but you might get away with using your same flywheel on yours. Good Luck !

 

the engine is physically the same on the outside, so everything will swap over and just bolt in place like it belongs there. you will need a new flywheel for the 1pcs rear main seal of the new engine. as stated a flysheel from an 86 and up will work. if the new block has the right bolts for the starter then that will work just fine as well.

theres a reason no fbody was offered with a t5 behind a 350. they dont last very long. if you baby it and drive like a grandma, then yea. but if you were planning on doing that, you wouldnt be swapping in a 350 now would you. save some cash and get an lt1 t56 drop out for about $1500 and put that in. you could swap in a 700r4, but who wants an auto?

 

is your 305 tpi or tbi? tpi will swap onto the 350 but will need a new prom and a new knock sensor. tbi requires a few more mods to feed the 350 well. if youre going to carb it, it takes more work, and some wiring. and carbing it technically isnt legal....

 

Your 86 has a 1 piece rear main seal, so you can re-use the flywheel. The t5 isn't real strong, but if it's in good shape it'll be ok behind a mild 350, at least while you save for something stronger. My t5 has been behind my 350 for close to 10 years now and it's still like new. So far I've run a best of 13.8, so the motor is nothing extreme. When I swap it into my gta with new heads, we'll see if it still holds up.

 

Thanks everyone for all of the input im starting to think the t56 is the only way to go even after reading about a few aftermarket rebuild kits such as gforce rebuild kit. Im just worried about all of the modification that will be involved just to keep the car standard trans with the new motor. Hopefully I can find the transmission alone at a junkyard

 

A T56 is definitely a great idea if you can afford it. I'm going to keep running my T5 mainly just to see how long it lasts. I'm hoping if I don't ever put drag radials on the car that the T5 will survive.

 

i agree, i swapped in the t56 built to handle some serious power well before i even started buying parts for the engine swap.....one of the best mods ive ever done to the car.

 

I'm thinking about doing the same thing with the 383 swap....
Did you use any adaptor harnesses and if so where did you get that harness? How does it run?

 

You don't need an adapter harness if you use the same type of induction that your old motor has, i.e TPI to TPI.

 

Mine was a carburetored engine and I went back with the same carburetored setup so I did not have to have any adapters/wiring harness. The engine runs great