Brandon from Furches Performance released a video at the end of last year detailing how he bolts a 4t80e up to an LS4. It boils down to relocating the starter to the oil pan, drilling the flywheel for the new torque converter bolt pattern, and a bit of material removal from the block and/or trans case. The LS4, and 3800 share the GM small metric bolt pattern. So with the same list of modifications, could a 4t80e be mounted to a 3800, or am I missing something? Also, I've tried looking around online for information on how Brandon shifts the 4t80e manually. I read in an article that it's an electronic mod, but thats all the detail I got from it.

 

Off topic a little but I like how he says "look at that little piece of s**t."

 

Yeah, it's been done before. There are some threads on other boards you'll find via Google. I'll post up a few of the links I found later from when I had researched it.

A few of the issues:
-you have to grind the back of the block at the mounting flange
-you have to relocate the rear knock sensor
-you may need to mess with adapting the range selector as not all 4t80s are the external on top of the trans case
-youll need to re-drill the flex plate. I've seen a few threads where there were already dimples in the flex plate (both HD and regular) that just needed to be drilled out. They had to use a hex head bolt to avoid hitting the counterweight though
-itll need custom mounts
-itll need custom axles
-depending on the year, converter lockup can be a problem as some are PWM
-there was also an issue with the solenoid logic, I remember something about having to change the output logic to the two shift solenoids as the on/off pairings didn't match the gears for the 4t65
-itll obviously need the tune adjusted due to the different FDR


The huge upside is the potential for a dirt cheap trans to hold big power. I've seen some of them used going for as low as $150 locally. They're also less likely to have been abused due to the cars they came in.

They do have a few downsides besides the custom work. They're notably heavier. They will consume more power (ie less of the engine power makes it to the wheels). Theres not really any aftermarket - any mods to make it better suited for racing are going to be totally DIY. Of course lastly, if you just plan to buy used and slap them in as most do, it's a crap shoot as to what you'll get.

IMO, given how stupid expensive built 4t65 stuff is getting, it's worth a try if you're comfortable with all the DIY stuff.

 

I found this thread on the chicago garage forum that has some helpful pictures. https://www.thechicagogarage.com/for...t60-65-hd.html
One thing I haven't found in regards to mating a 4t80e to a 3800 is starter placement. Brandon mounts his starter to a modified LS4 oil pan, that already had somewhat of an accommodation for it. Would a similarly modified 3800 pan be the way to go?

 

TBH I dont recall seeing an issue on the 3800. The LS4 mounts the starter on the trans instead of the engine which is what causes issues swapping to a different trans.

But honestly other than a few months of research a year or so ago, I have zero hands on experience.

You nailed one of the threads, below is another i had saved.

4t80E trans swap

Turbo400sbc had a lot of threads on it across various forums, so may be worthwhile to search that screen name with 4t80.

Biggest thing that stuck out to me that needed to be nailed down (once decided to proceed of course) was what FDR, TC lockup type, and range switch you wanted as the trans was offered for so many years.

 

I just crawled under my monte and verified that the starter is indeed mounted to the front of the engine. Lol, TBH, I completely neglected to think where the starter was mounted on a 3800 rather than where its mounted on an LS4. The only possible problem I could think of with that would be having to modify the bell housing a bit more to accomodate the starter. But thats only if the bell housing dosn't fit right over the starter to begin with.

Yep, I definitely need to look into those. Any opinion on what would be best for the setup I'm building up towards?

I didn't really find this swap to look that difficult, although hindsight might change that statement. The starter was my biggest concern. Having to fab something to get the starter mounted. But now that that issue has been resolved, my next biggest concern is how I'm going to install that massive trans. I've thought about dropping the subframe, and installing from the bottom. This would likely require a lift, which I could probably rent locally. Theres a technical school that offers additional more specialized classes to the local high schools. I'd have to call and ask about using one of the automotive lifts there.

Next on the list would be axles. In the comments of the LS4 to 4t80e swap video, Brandon says that he uses stock axles from a few different cadillacs, but doesn't say what models or years.

Another item on the to do list is the controll of the trans. Brandon's is shifted manually, and i would really like to replicate that. Ever since my little brother got an 83 Ford F250 for his first vehicle, I've been itching for a manual shifter in my car.

 

Not particularly as it's been awhile since I researched that option. Obviously TCC lockup would be based on what you end up using to control it.

FDR is the tougher one. Most drag setups tend towards the higher FDR, but with a high power setup on the street, you'll have a tough enough time hooking the low gears on a street tire anyways. So maybe that pushes towards a lower FDR or maybe that keeps you from dig racing on the street altogether in which case youd want a FDR that works best with the roll mph you want to focus on (ie not starting you at the bottom of the next gear up at the speed you want to go from.


I agree, it doesnt really seem too crazy. Certainly a lot more work than dropping in a built 4t65, but it has the potential to save a lot of money.

I know there are standalone transmission controllers thatll allow for shift button inputs. That route would also eliminate having to tie in the stock pcm to the trans as youd just set the tune up like it was connected to a manual trans.

Only thing I wonder with those is how responsive the trans is to manually forced inputs. Just thinking if it was like the paddle shifters on my 4t65 GP GXP, there was so much lag that it almost wouldn't be worth it. It was so much worse than modern transmissions that were built with that functionality up front. I worry the 4t80 might be worse as it was used exclusively in semi luxury vehicles so it may not be as apt to performing quick shifts.

Definitely worth picking Brandon's brain if you can get in touch though.

Another thought - have you tried reaching out to Triple Edge Performance on their input? If I recall correctly, they had their hands in one of the 4t80 swaps out there. Being one of the leading experts on these cars / transmissions, they might be able to offer some insight also as to the potential pitfalls and such.

 

From the Chicago garage thread I linked, it seems they had the best luck with the 3.48 FD ratio.




I found this eBay Trans Controller for 420$. It seems promising for a reasonable price. As far as the laggy shifts, we may just have to see about that one. It might be fixable with that controller, if it is an issue.

Just shot them an email.

 

I just heard back from David over at Triple Edge Performance. He reiterated most of the basic info already in this thread, but also said that the trans needs some upgrades in order to really hold higher HP levels. I asked him to elaborate on that and am waiting on a response. Other than that, he also said a better torque converter would help things out. I can't really find a site that sells high performance 4t80e torque converters. I did find this Remanufactured Transmission for 1700$ though.

 

Glad you heard back, they're always very helpful over there.

Maybe he can get you on the right track with a converter shop also? If not, I'd try contacting some of the big converter shops to see if theyve done one before, I'm sure at least one of them has.