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4L80E trans question

Allisons, even used and/or rebuilt, are not cheap. They're also larger than a 4L80E/6L95E so there could be fitment issues. The nice thing about the 4L80E is that it's a TH400 at heart with an OD section and all the tricks/parts that make for a super stout, bulletproof TH400 work on D, 2, 1 and R of the 4L80E, too. There are also aftermarket parts/fixes to make the OD and lock up torque converter more stout/reliable, too.
 
Handling the work load and lasting a long life- you have very few choices for an automatic.

Th400 is 3 speed with zero electronics. But 3rd gear is 1:1. The 4l80 is the equivalent of a th400 with override of .75:1. That 25% drop in rpm on the hiway is HUGE!!! So if you get a th400, you now need and external over/underdrive to deal with the lost top speed or lost acceleration if you change the differential gearing to make up for it on top.
Yes the 4l80e is electronic and costs about a grand for stand alone controller-
The other vairiants- 4l85, 4l90,6l80 -85 -90 etc.... are the same basic transmission with upgrades.

Above that is the allison transmissions and you just shot price through the roof and controlling them becomes a nightmare. Diagnostics is just as hard if not more.

Honestly you should have a 4l90e for longest life in the rv with that weight and engine.

Otherwise it is time to install a clutch pedal.

Proper operation temperature- and fluid/filter changes with good atf- you should get 200,000 miles for that trans.
 
ak diesel driver said:
My understanding is that a 6l80/90 is closer design wise to an allison than a 4l80
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Could be, but my understanding is the 4l80,85,90E all handle the torque or really heavy rigs much better and why they go behind the diesels, until it is too much then jumps to the allison. That’s why I wasn’t thinking closer to allison.

The better od ratio always caught my eye being as my final drive is 5.31 playing with the 37” tires.
 
@Paul McDaniel if you contact @3bals, he currently is in the process of parting out his P-30 chassis-based Trek motorhome (see the thread Goodness, Gracious, 3bals Afire!, if a Moderator could post the link to that thread here, highly appreciated, as I can'tfigure out how on my phone) that caught fire while on vacation. He had put a seriously built P400 6.5 in it AND a seriously bullet-proof, VERY stoutly built, Road Ripper* 4L80E transmission that has very low miles on it and had NO problem handling the weight and air resistance of the motorhome AND the car it towed!

I am SURE Jody would be more than willing to accept a reasonable offer for it. I know the company that built it, it is a local, multi-generational family-owned transmission shop that builds automatic and manual transmissions for commercial fleet use, daily drivers and racers. It has all of the heaviest-duty upgrades - clutch materials, steels, bands, sprags, drums, valve body upgrades, etc, etc, etc available.
 
Will L. said:
Could be, but my understanding is the 4l80,85,90E all handle the torque or really heavy rigs much better and why they go behind the diesels, until it is too much then jumps to the allison. That’s why I wasn’t thinking closer to allison.

The better od ratio always caught my eye being as my final drive is 5.31 playing with the 37” tires.
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Well, @Will L., if you go with the 10L1000 10-speed Allison currently behind the 6.6 Duramax, you get a .63 tenth gear! Time for that H1A1 body lift kit install?🤔🤔🤔
 
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@Will L. Yup. That's why GM upgraded the 4L80E to the 4L85E (basically clutch/steel and band upgrades) to put behind a detuned 6.6 Duramax in the 2000's G series vans, as the Allison wouldn't fit without either some serious body lift (not desirable for a cargo van) or floorpan/doghouse redesign that would reduce already confined seating/access. I would love to find an early D-Max van and get that combo to put into a 2WD Burb with a 3.23 rear for some serious HWY MPGs!
 
dbrannon79 said:
I was told that a 6l80e was simply a 4l80e with half gears bewteen each of a 4l80. the 6l90e was a whole different animal.
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Not even close, you're thinking of the Jet 6 speed which used a 4l80e trans, different planetaries to change the gear ratios, modified valve body to add a dedicated overdrive solenoid, and an aftermarket TCM to engage overdrive between gears to split them. Only 5 of the gears were really useful as 2 almost overlapped. The 6l80/90 are a clutch to clutch trans like the allison 1000.
 
Husker6.5 said:
@Will L. Yup. That's why GM upgraded the 4L80E to the 4L85E (basically clutch/steel and band upgrades) to put behind a detuned 6.6 Duramax in the 2000's G series vans, as the Allison wouldn't fit without either some serious body lift (not desirable for a cargo van) or floorpan/doghouse redesign that would reduce already confined seating/access. I would love to find an early D-Max van and get that combo to put into a 2WD Burb with a 3.23 rear for some serious HWY MPGs!
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There's only a handful of changes between a 4l80e and a 4l85e. An extra gear in the planetary assembly's and an induction hardened output shaft iirc. That was it. No clutch changes, no band changes, nothing like that. Hence why it only upped the torque input rating from 440 ft lbs to 450 ft lbs. And the 4l85e came out in 02 originally for the 8.1l Suburban & Avalanche and was later used behind the Duramax in the vans for a short time until the 6l90e was available.
 
Husker6.5 said:
What about the wider Reverse band in the 85 vs. the 80, @THEFERMANATOR ?
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All 4l80/4l85/th400 from 95+ use the same reverse band, and the new style band retro's back to older models(same size, they changed the way the friction is designed). You're thinking of the intermediate band which was changed to a wider band starting early 99(March or May iirc). It is only used in shifter position D2 for engine braking.
 
So which is the best option? I also have a large van, step van 1985 1 ton. Also has a 350, the motor has a bad knock because one of my ex employees drove it. Highway speeds more traffic, it just doesn't hold up to normal driving.
Engine 350
Trans 400
Rear 4:10
I was thinking vortec 454/4l80e 2wd so I have obd2 for tracking speed location etc.
I have k3500s with this and it's a good setup but I don't really carry or pull much weight with them.
I drive a 2015 duramax and the transmission shifts so smoothly, my wife actually stays asleep as I drive when we go on camping trips. This is not the case with the 454/4l80, does the 2006 8.1/allison 6spd shift smoothly?
If so, is it possible to put that allison behind a 350 or 454 or a better option?
 
Interestingly, after weeks and weeks of waiting, I had a qualified mechanic check this out and all grounds, ignition, etc., seem to be functioning fine. The 1-2 and 3–4 shift modules were replaced but the vehicle still will not shift past second while in drive. He thinks next an answer may be to replace the solenoids which evidently entail draining the transmission fluid and pulling the pan to get to those. No mechanic that has looked at this vehicle thinks there is a mechanical/gear issue with the transmission, so I am hoping replacement of the solenoids fixes the problem. We’ll see.
 
Dustin, no dumb questions, and I’m not sure myself. Back in March the good folks on the forum gave me some interesting answers to what might be causing my problem (lack of the ability to shift between the automatic gears, which was an intermittent problem). I’ll hopefully have a functioning transmission after I get the solenoids replaced. if that doesn’t work I’m not sure what would come next aside from a new transmission.
 
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