SBC Transmission Opinions

[Anthi4078]

Hey I’m going to be swapping the engine in my truck for a tuned port from a C4 corvette eventually. I'm torn between using the 700r4 from the corvette or adapting a AX15 to it. I am a big fan of manuals but I feel like the auto might be a better choice. Just curious your guys opinions or what you’d do if it was you. By the way this is purely a street truck. So off-roading ability doesn’t matter lol. Thanks, Andre

[89 MJ]

I’d find an NV3500 out of an 88-05ish GM truck. Then it’s using all GM parts, none of the fancy conversion bellhousing or anything like that.
I do also really like the 700R4, my mom had one in her 46 Chevy and put over 70,000 miles on it with no issues, my brother has one in his J10 that sees off road use and has had no issues, and I’ve got one in my 40 Chevy pickup and it has been fine for moving the truck around for over a decade, but it hasn’t seen the road yet. 

At the end of the day, I’d recommend using a GM trans for simplicity. Then it’s just your preference for a stick or an auto. 

[pizzaman09]

Of you are going to build it, do what you want.  If you want a manual, do it with a manual.

 

Out of curiosity, why the tuned port SBC?  

[Comanche SS]

2 hours ago, Anthi4078 said:

Hey I’m going to be swapping the engine in my truck for a tuned port from a C4 corvette eventually. I'm torn between using the 700r4 from the corvette or adapting a AX15 to it. I am a big fan of manuals but I feel like the auto might be a better choice. Just curious your guys opinions or what you’d do if it was you. By the way this is purely a street truck. So off-roading ability doesn’t matter lol. Thanks, Andre

As someone who has had V8 MJ's with a 5 speed, 6 speed, 4L80E and a 700R4

The 700R4 would be the last transmission choice of the lot.

[Anthi4078]

15 minutes ago, pizzaman09 said:

Of you are going to build it, do what you want.  If you want a manual, do it with a manual.

 

Out of curiosity, why the tuned port SBC?  

I want to keep it fuel injected and my grandpa happens to have a smashed up 87 with only 125k km 

[Anthi4078]

2 hours ago, 89 MJ said:

I’d find an NV3500 out of an 88-05ish GM truck. Then it’s using all GM parts, none of the fancy conversion bellhousing or anything like that.
I do also really like the 700R4, my mom had one in her 46 Chevy and put over 70,000 miles on it with no issues, my brother has one in his J10 that sees off road use and has had no issues, and I’ve got one in my 40 Chevy pickup and it has been fine for moving the truck around for over a decade, but it hasn’t seen the road yet. 

At the end of the day, I’d recommend using a GM trans for simplicity. Then it’s just your preference for a stick or an auto. 

Hmm I’ll keep on the look out for one of those. There’s literally none on my marketplace right now lol. I’d like to use a NP242 for the AWD option so I’ll probably have to end up adapting something one way or another 

[Anthi4078]

11 minutes ago, Comanche SS said:

As someone who has had V8 MJ's with a 5 speed, 6 speed, 4L80E and a 700R4

The 700R4 would be the last transmission choice of the lot.

Why do you say that? And what were the two manuals you used?

[89 MJ]

22 minutes ago, Anthi4078 said:

Hmm I’ll keep on the look out for one of those. There’s literally none on my marketplace right now lol. I’d like to use a NP242 for the AWD option so I’ll probably have to end up adapting something one way or another 

The NP242 does throw a wrench into things. Of course, if you aren’t going to use 2 high or 4 low, you could use a NV149 or NP149 which were the AWD t-cases used in GM vehicles in the early 2000s. For long term parts availability, I prefer using OEM parts instead of needing adapters by various companies. With the number of well known adapter companies, that’s a fairly weak argument though. 

I also want to be clear that I’m not trying to tell you how to build your truck, this is just some food for thought. 

[Anthi4078]

27 minutes ago, 89 MJ said:

The NP242 does throw a wrench into things. Of course, if you aren’t going to use 2 high or 4 low, you could use a NV149 or NP149 which were the AWD t-cases used in GM vehicles in the early 2000s. For long term parts availability, I prefer using OEM parts instead of needing adapters by various companies. With the number of well known adapter companies, that’s a fairly weak argument though. 

I also want to be clear that I’m not trying to tell you how to build your truck, this is just some food for thought. 

Yeah no I appreciate your help. I don’t know much about the GM stuff so those transfer case suggestions are awesome. Time to start researching them 

[TurboedMJ]

If I'm going with a GM automatic it's gonna be a 4l80e (for most applications, if it's diesel I'm getting an Allison.) very popular and easy to get parts for. However, if your building a street truck, I'd find a manual that will fit. It will be much more fun that way

[pizzaman09]

20 hours ago, Anthi4078 said:

I want to keep it fuel injected and my grandpa happens to have a smashed up 87 with only 125k km 

That's a good enough reason for me!  Hopefully the engine is easier to work on in a Comanche, I've seen some videos of those tuned port SBC engines and they look challenging to work on with their factory accessories.

[derf]

There's nothing wrong with the 700R4 out of the same donor as the engine.  Keep all the parts together and it will work fine.  Rebuild the transmission with common upgrade parts and it will be a solid choice.  Get an adapter from Novak or Advance Adapters and swap the tail shaft while you're in the transmission.  Then the 242 bolts right up.

 

The 4L80 is a tight squeeze in the transmission tunnel and it's overkill for a small block.  Besides, the 700R4 gives you both a deeper first gear and taller overdrive.

 

For manuals, the AX15 is my first choice followed closely by the NV3500/3550.