4l85e

[Arr]

Could someone school me on the pros and cons of using a 4l85e. I just picked one up and would like your input as to whether or not it's a viable trans for Bonneville. If it is, what modifications would you recommend?   thanks, Arr

[Sumner]

What kind of car is it going into?  Are you going for a record or just running?

Personally I'm not a fan of the gear ratios of any of the  OD transmissions that are only 4 speeds.  Again it depends on the car, the speeds you are trying to run and the HP/Torque available and the RPM range where the HP/Torque resides in.

With Hooley's Stude we ran a 1.93 first and still couldn't run wide open in 1st or second so it could of been taller.  4th was a .93 overdrive which we liked on the top end.  This was with a 6000 lb. car and probably 850 HP running 250.

You might want to use a spreadsheet where you can plug in different variables and see what the rpm is before and after a shift to see where you would be in your engines power band (see if it will pull a 25% overdrive drop in rpm)....

http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

Sumner

[kiwi belly tank]

The 4L80E is a great trans. It is basically a TH400 with O/D & a lock up & many of the parts are interchangeable. The reason many people don't use them is because they are ECU controled but you can get a stand alone controler for about $600 or you can make it a full manual at home with some micro-switches & a ratchet shifter.
We stuck a "used" stock one with a good converter on the back of a twin turbo Duramax in a street rod six years ago. It's done Drag Week & we road tripped it there & back, a few drag meets, some street racing & lots of road trips & it's still going strong.
We figured on getting it running with the used trans then building a good one but if it ain't broke!
We've broken the engine & the Jones quickchange but not the $350 used trans that had over 80k miles in a van.
  Sid.

[Arr]

Doesn't the torque converter help with ratios? Car is a Lakester with a 302 GMC, the records start at 200 and they just go up from there. Reasonably, the engine in XO form will be doing good to get 450/500 horsepower on gas. With the option of the XX head and a blower on fuel, well horsepower could be as high as possibly 1200 but that is a long way off. Thinking of building the floor pan like a bucket, to hold the parts when they come out.

[Arr]

That's good news! This one should have the extra pinion in the OD as it's an 2004 4l85e from a Duramax van
. Manual shift with a vacuum modulator to vary the pressure was my first thought. There's a 10" converter with dual clutches for sale here, I think they said it had a 3800 RPM stall converter. So far, this seems viable.

[gnomenator]

Hi Arr, I have built many a racing tranny for everything from drag race to rock crawler and my own 4L60 in my 53 Stude Bonneville car behind a 496 BBC. Any of the overdrive trannies work if built correctly($$$) . But as others have replied, it depends on vehicle. That said, I believe you may be on the wrong course with a large stall convertor. Those work great for drag racing where you need to reach stall speed in the engine band in order to launch correctly. IMHO , I feel a 'tight' converter works much better on the salt. You are somewhat correct, the converter doesn't affect ratio but if you do the computer thing, when the lock-up occurs, the 'slip' is gone.That's the issue with hi stall; they are slipping till you reach stall, so a lot of power is lost. And if you run a hi gear(low number)diff, it will seem like forever to get it going. You can manually engage lock-up after you get  rolling , but that's just one more thing to thinkabout/do when you at after it    If you would like to chat, pm me and I'll send you my number- good luck   one more thing 4L80 is a very big , very heavy trans !

[Arr]

I will call thank you.. One of the problems I foresee with this trans is the parasitic loss of just having it. Coupled with the Ford 9's power consumption they will take a lot of HP I simply don't have. With that thought in mind, is it possible to leave the reverse band and actuator out altogether? REM the internals and maybe using an oil shedding coating?  All of that is available here locally. I didn't think a 3800 RPM stall converter was that radical but the stock diesel on is still with the trans and I simply don't know.  This entire thing came up because the early Chevy aluminum T-10 (with R-11 overdrive), I also have, might be too weak in the other classes this engine might run in.

[RaceEngineer]

Oil sheading coatings won't improve efficiency enough to be meaningful.  The power consumption is in the hydraulic pump (pressure x flow rate) and in heat due to shearing of the trans oil in the converter and to a lesser degree in the clutch packs.  The high stall torque converter is less efficient than a stock converter.  As stated it is used to launch from a standing start at higher RPM so at higher hp.  Not needed or beneficial in LSR.

[Arr]

RaceEngineer, thank you for that. Just had a great conversation with gnomenator. As I am so HP limited the 4l80e is just too much for the place I'll be at in the beginning, maybe later but not now. Your words of wisdom pretty much put the last nail in this one. I still have that T-10 and it may be the best way out for now.