Hey! First of all I want to thank all who frequent the boards and answer questions; you're a godsend. Here's my situation:

I have a stock '92 firebird V8 5.0 base model. It's an automatic and should have the 4l60 as that's what was going into those in '92. (could be a 4l60e). My ultimate goal is to swap the engine with a carbed 350 (MAYBE a 383), and I keep hearing that the 4l60 / 700r4 is a POS behind anything with real power. Even if I go with a 350 it'll have ~300hp, 70+ more HP than the trans-am in that year. So, since I will have to upgrade the tranny anyway when I do the engine swap I am leaning toward swapping the tranny first and going to a manual, but I want to ensure that I get a tranny that's going to be able to handle power from a beefy 350. I would rather not spend too much money, and I will be having my mechanic do the work (I don't know much about installing a shift kit). The questions are:

- Should I even consider swapping to manual? Or just get an automatic upgrade?
- what transmission should I go with? Keeping in mind I plan on swapping the engine with a sbc 350 carbureted and want to ensure it'll match up
- Should I wait and do the manual transmission when I do the engine swap? I'd like to do them both but money is an issue, I can't finance both at the same time any time soon, but I certainly can do one, either engine or tranny, and since I'm partly convinced I have to do the tranny anyways I figured do that first...

Again, thanks in advance.

 

Well... the other bad news is the manuals in these cars are even weaker.

It's pretty expensive to swap a decent manual trans into an auto car. I think you'd be money ahead doing upgrades to the auto. And the car will hook and book better too.

 

An auto to manual swap is not going to be inexpensive, especially if you are paying a mechanic to do it. The T-5 5-speed that came in the thirdgens is weaker than the 700-r4 auto. A T-56 6-speed from a 4th gen is pretty strong and should work fine for what you are describing, but will be pricey.

The 700-r4 can be made to handle a good amount of power. Unless you just want the manual, I would run the auto. Do a shift kit for now and if you burn it up, have it overhauled using upgraded parts.

 

Thanks, QwkTrip and TransamGTA350!

That's what I'm hearing. Can you link me to a decent shift kit so I have an idea? That might just make it fun enough to not jump into the deep-end with a manual trans.

 

Some people like the B&M or Transgo kits. I’ve never used one, so can’t say they’re good or bad. When I had my 700-R4 rebuilt years ago, instead of a traditional shift kit, the transmission shop installed a Corvette pressure regulator, a Superior Super Servo and a B&M 3-4 upshift valve. It had very nice part throttle manners, but would chirp the tires on the 1-2 upshift at WOT everytime. All of that could be done with the transmission in the car.

 

The answer to which transmission shift kit is never B&M.

garbage that just increases line pressure. Not only does that cause unnecessary driveline shock it is also harder on the transmission internals.

TransGo with optional upgrades all the way.


and while yes. To those in the know a 4L60 is a 700r4, most people do not refer to the ones that came in the third generation as a 4L60. It was known as a 700r4 when the thirdgen was in production.


https://probuiltautomatics.com/shop

I have, and always will recommend Dana @ probuiltautomatics

I say get the TransGo shift kit with everything. You will love how it transforms the slushbox without becoming a harsh painful thing to drive.

smooth but positive at light throttle with progressively firmer shifts as you increase throttle.


now. Costs for a good performance rebuild vs manual swap?


similar. Both expensive. Especially if you have a shop do it.

if you go manual go you have some options.

Tremec TKX is a new option for 5 speeds. Magnum F for 6spds.


Cheaper is a used t-56. But that will still set you back too. The used t56 market has always been a hot item. Most get ripped out before the car ever makes it to the yard.

 

Just to add another comment, if you are talking about 300hp at the motor, that’s not really too much for a 700r4 with a shift kit. It will be harder on it than the stock motor, but it will probably live a long time at that power level. If it does eventually need a rebuild, you don’t need to go nuts and build it to handle 450hp. It gets expensive quick and not needed for your application. There are some easy upgrades that can be done during the rebuild that will make it solidly handle 300hp.

 

That's good news. Appreciate the info. I'm on the fence out swapping, need to talk to my mechanic as well. Thanks!

 

Because your mechanic knows more about third gen F bodies than the sum total of all the members of this forum that have answered you? LoL.

We keep trying to tell you - paying a mechanic - with your meager budget - is really stupid. Seems to me that you are like everything else in the this world - want all the fun without any of the work and half the cost.

You have to pay to play. Either with money (a LOT of it for what you want), or with sweat equity. Trust me - a decently fast third gen with 300 RWHP is going to cost you $10k-$15k one way or another. If you do it yourself you will get better parts. If you pay someone..... good luck with that.

GD

 

I just hope the mechanic that butchers your EFI system for a carb does a good job

 

I'm getting mixed info on the carb.. so I may not even go that route. Just keep the TBI.

That's one of the headaches of this thing is that depending on who you ask you get different information, which is why I like to talk to both you experienced ppl and my mechanic to determine the best course. I'm warming up to the idea of doing it all myself, trust me.

 

Tough crowd here, but I do agree. I would not be ripping off the EFI system and replacing it with a carb. No good reason to do that.

Do some nice upgrades over time, as budget allows (air intake, exhaust, headers). When you are ready, a motor swap is fine, but the TBI system with some upgrades can handle the 300hp 350 you mentioned and it will be so much better than a carb.

 

I laughed at "Tough crowd here". You ain't kiddin'. But you gotta take the sour with the sweet, right? Thanks a bunch for the time and info. When I first had this idea, the plan was to pull a motor and build it, then as time goes by you don't end up having the time / equipment so you consider other options, but I'm glad I initiated this convo. If anything, I may end up where I started, wanting to build up an engine, invest in the tools, etc.

 

My car was carbed from the factory but the PO removed the Q jet hacked everything and added a 350 and edelbrock. I have spent years fixing wires and working on tuning. It runs decent now but a sniper EFI is in my future,

 

ProBuilt Automatics built my transmission about 4 years ago. Its been through a lot of autocross, short course road course, drag racing, and heavy street driving. It has been great. Made 45 drag strip passes on it this year alone and its never skipped a beat. Its the ProStreet Elite package of the 700R4.

 

I swapped a TH700 for a world-class T5 behind an L98 B2T. As long as I do not use anything stronger than a stock clutch setup, the T5 should be perfectly safe (the clutch will slip before the transmission breaks). So far I've beat on it in my convertible for about six months. It's been fine. Waaaay more fun. No mods needed to the TPI.

A few notes from my experience:

1. Cutting the holes in the firewall for the clutch system is very important to locate correctly. With the engine in there, it is pretty tight on the engine side. You will also want to reinforce the master cylinder mounting area with an extra layer of sheet metal.
2. Swapping out the two pedal assembly for the three is uncomfortable work.
3. Minor electrical changes (starter lock out (P-N position) and the reverse lights
4. Different trans support cross member
5. Best idea is to find a donor car and get every piece from there.
6. Make sure to get a tailshaft plug. Far less messy!

 

That's good advice. Thanks!

 

You can have a fun car with the TBI especially if you swap over to a 350. Even with the 305 TBI after I added 3.73s, posi, S10 torque converter, built 700R4 with a nice shift kit,and 3 in exhaust it felt like a different car.