3400 engine/trans in a '96 Grand Prix?

[Brodizzle83]

Looking at a cheap and easy option/upgrade in case my 233k mile 3100 decides to shit the bed. Before this car I drove my dad's 2001 Impala with a 3400 and it felt much snappier than my '96 GP and that car had just turned over 200k miles. I'm sure the engine would be a direct replacement to my 3100 with no modifications, but I could be wrong. Also, I saw that my transmission is a 4T60-E and the newer cars have a 4T65-E. Would that transmission also be a direct swap or not?

 

Sent from my SM-G955U using Tapatalk

[Psych0matt]

I’m not sure how easy it is but 3500 engines are modern and pretty nice imo though my only experience is the one in our van. I’ve heard they like boost though... I would think that they’re a bit more plentiful at this point

[55trucker]

The LA1 (3400) is an OBDII engine only, it is for all intent & purposes identical on the exterior to the smaller L82 (with the exception of the casting in the upper plenum), it would be a direct drop-in for you.

 

The rear exhaust manifold flanges are 2 1/2" on all the LA1's & the rear port is in the center of the manifold whereas the manifold flange attached to your engine is located on the rear end of the casting, the L82 is a smaller dia. (not sure if they are 2 1/4" or 2") so one would need to fab a 2 1/2" downpipe/cat  from an LA1 vehicle & fit it under the GP so one doesn't lose the flow capability, the only other 2 1/2" downpipe/cat combination used under a Gen 1 is with the DOHC engine.

 

There shouldn't be any tuning issues as the injectors used in both engines are the same & the fuel trims are near identical.

[Brodizzle83]

Awesome, good to know! Since this is my daily with no back-up, I wouldn't have the time/money to do an L67 swap like I would love to do, but the 3400 is a fun lil engine as well.

 

Sent from my SM-G955U using Tapatalk

[Brodizzle83]

Now what about the transmissions? Would the 4T65-E be a direct swap for the 4T60-E that I have? Or would that need the custom axles like the L67 swaps need?

 

Sent from my SM-G955U using Tapatalk

[55trucker]

why would one need to go to the *65*?

 

The *60E* is more than stout enough behind the DOHC engine, the pushrod LA1 engines low end torque #'s are a bit better than the DOHC but nothing that would destroy that trans, personally I don't see the point.

 

The 65 was used behind most* of the later OBDII LA1 installs but the 60E had been discontinued by then.

 

*some of the smaller platforms that got the LA1 were backed up by the smaller 4t45 trans.

[Brodizzle83]

why would one need to go to the *65*?

 

The *60E* is more than stout enough behind the DOHC engine, the pushrod LA1 engines low end torque #'s are a bit better than the DOHC but nothing that would destroy that trans, personally I don't see the point.

 

The 65 was used behind most* of the later OBDII LA1 installs but the 60E had been discontinued by then.

 

*some of the smaller platforms that got the LA1 were backed up by the smaller 4t45 trans.

Gotcha...makes sense. Just wasn't sure if the newer trans was a much better trans or not.

 

Sent from my SM-G955U using Tapatalk

[Nas Escobar]

I think the only good thing that the 65 has over the 60 is that the rod for 4th gear/overdrive doesn't stick and cause the trans to limp down to 3rd gear. Other than that, there's no real advantage of going 65 unless you randomly had a 98-99 Z34 Monte Carlo with the 3800 and the 65. That would be the easiest way to "modernize" the 96 GP.

 

As far as the LX9 goes, my understanding is that the blocks don't plug and play... at least that's the way it goes in the J body world. The LA1 will bolt in but requires a custom mount in the front whereas the LX9 is a different beast, but in that application the 3.1 was the infamous LH0 and not the L82. It may work in between the L82, LA1, and LX9 considering the LX9 is supposedly a bored over LA1. 

[rich_e777]

The LA1 (3400) is an OBDII engine only, it is for all intent & purposes identical on the exterior to the smaller L82 (with the exception of the casting in the upper plenum), it would be a direct drop-in for you.

 

The rear exhaust manifold flanges are 2 1/2" on all the LA1's & the rear port is in the center of the manifold whereas the manifold flange attached to your engine is located on the rear end of the casting, the L82 is a smaller dia. (not sure if they are 2 1/4" or 2") so one would need to fab a 2 1/2" downpipe/cat  from an LA1 vehicle & fit it under the GP so one doesn't lose the flow capability, the only other 2 1/2" downpipe/cat combination used under a Gen 1 is with the DOHC engine.

 

There shouldn't be any tuning issues as the injectors used in both engines are the same & the fuel trims are near identical.

I really need all the swap info i collected about this from my laptop. One thing I remember someone telling me is that for a 3100 to 3400 swap one would need a PCM with a removable prom chip to retune for the 3400. Usually found in the earliest 3.4 DOHC cars. I`m planning on doing a 34oo swap as well to accommodate a UB3 cluster in my 94 CS and want to make sure I got enough info and parts info before starting.

Edited June 20, 2018 by rich_e777

[19Cutlass94]

How is the 3400 a OBDII engine only?! I swapped one in mine several years ago and ran it on the stock 1994 PCM with no issues...

 

It’s one of the easier swaps there is. Y’all are making this much harder/bigger deal than it really is..

[l67ss]

I ran a 3400 on 3100 stock tune just fine. Should you wanna t65 swap you need a harness from a 00-01 lumina and pcm from same car with gear ratio corrected

[55trucker]

How is the 3400 a OBDII engine only?! I swapped one in mine several years ago and ran it on the stock 1994 PCM with no issues...

 

It’s one of the easier swaps there is. Y’all are making this much harder/bigger deal than it really is..

It did not come along until 1996, it was an OBDII engine,

 

I didn't say it could not be used in an OBDI environment, I've done half a dozen conversions into Fieros myself as well.

[Brodizzle83]

Well now reading a little into the 3500 LX9 and might be a better swap. Sounds about just as easy and more power. Also sounds like GM "fixed" the valvetrain noises in this engine and they're more economical as well.

 

Sent from my SM-G955U using Tapatalk

[55trucker]

If you're planning on installing the LX9 engine note that the throttle is *drive-by-wire*. To install that entire engine into a non *drive-by-wire* vehicle you'll need the available adapter that is out there to mount a cable throttle body to the intake manifold.

 

If I remember correctly the 3100/3400 dampener is also required for the trigger mechanism, and the LX9 fuel rail has to be replaced as it is a non-return design and there are other small mods related to the intake manifold that need looking after.