3l80 vs 6l80e

[bru21]

So its nearly time I buy a trans.
I had my heart set on a full manual th400 - but they are dear - about 10k for a desert US built one. I am not sure at this stage why they cost this much but many TT teams spend 20k etc.

I always think new is better - (especially with the full bellhousing and the correct bolt pattern form my LS2) and I have found these:

http://holmart.com.au/online/prod355.htm

so essentially the gears are new where as the th400 are 1970's etc.

I am told you can get full manual valve bodies for these.

So obviously on the TT with 37's I won't need 5th and 6th but at only 450-500hp I am thinking an extra gear may be good (the US trucks don't have the 6.0lt rule and run 800 odd hp in a similar truck). Also If i still go ICV it might be handy on the road.

What are peoples opinions of this box as a package (including tail shaft options) - remembering I still have the option of computer control.

In theory the 80 means the 3l80 and 6l80 have the same torque rating but I don't think the 6l80 uses shift bands? The 6l is also heavier at nearly 100kg!

Ideally I can keep the box under 10k complete and have something I cannot really break in 'general' use which is of course racing.

I am trying to have a zero DNF record and have fun with this car rather than chase 1st place.

Gear ratios are

1 2 3 4 5 6 R 4.027 2.364 1.532 1.152 0.852 0.667 3.064

My diff ratio is: 5.43:1

here is some trans info:

http://www.cadillacfaq.com/stsfaq/tsb/d ... 30-023.pdf


cheers bru

[bru21]

http://www.compperformancegroupstores.c ... gory_Code=

another option based on the 4l80e

[6.5 rangie]

Whats sort of horsepower are you putting out?

[VooDoo]

Ring Craigs Auto's in Chipping Norton Sydney. He can build you a box to hold pretty much anything you throw at it. The 4L80e is a tough box but heavy. The 6L80 isn't really n option as its way too expensive and there is less room to beef up the parts. A manualised T400 isn't that expensive and are pretty tough. Craig builds Auto for some of the fastest drag cars around but has a lot of experience in off roaders too. Its worth having a chat to him. No BS, just facts and he backs his work. Ill get his office number and post it up in a sec.


(dunno if you remember the CAPA ute that ran 8's, thats his car)

Edit: Office phone 02 97551158

[bog warrior]

Talk to Alan at Artcarr. We are putting one of his boxs in our Patrol. Good price for what we got.

[HUSSLN]

I have a bloke here in vic who can build a t400 to handle 500hp+ for under 5grand mate PM me if you want his info. Shipping wont be an issue. Have quite a few mates running his auto's with nothing but smiles.

[KiwiBacon]

3 or 4 gears compared to 6.

I think the answer is right there.

[bru21]

I'll look into some of those leads.

What I'm worried about is not getting what I need and promised the earth. There wouldn't even be 10 TT's in the country and most of the bigger ones were built in the US.

Desert Autos are quite different to drag auto's.

For starters the hp rating is a lot lower due to constant abuse - some say 20% some say more. Also the torque converters have very very low stall converters, and accelerate poorly but generate far less heat. Also things like coolers are massive, shifters are different and don't ratchet. The housings can be different - especially the output housing with larger roller bearings etc.


Does anyone know a supplier where I can get a 2wd 6l90 (stronger 6l80)
I think they are in a chev 2500 or similar.

What ever happened to the wholesale transmission expert that was on here a while back?

thanks fellas,

bru

[1MadEngineer]

Bru,
you know the answer! you just haven't realised it....

the torque ratings are for 1:1 so if you use a 6 speed then the max rating is reduced once in overdrive. (Just like the age old drama of towing in 5th gear in a manual) so if 6th is 0.667 you have to consider the box will 'reliably' only handle 2/3 of the rated torque (give or take a little bit).

That is generally why common 3 speeds are used. Really once you have an engine that has 500+ real HP accellerating using 3,4,5 or 6 gears is usually only limited by traction not by ratio. Quite a lot of drag cars run 2spd PG and they accel fine and they have traction, you will be feathering the throttle struggling to get power down most of the time in short coarse stuff.

[bru21]

Thanks mate,

I was assuming I could delete 5th and 6th from the programming and run it as a 4 speed. (as per first post)
I know heathgu deletes 1st on his allison for drag use.

I am sort of worried as my gen3 nissan really sucked between 2nd and 3rd but it was only 400hp. I had to milk it and it always felt slow.

Initally this thing will have only 450hp fwhp.

I was thinking along the lines of 4 speed, quicker shifts and a tiptronic lever - or padle shift (might be Grimace) also It has clutch to clutch shifting.

[nzdarin]

With that much hp offroad you just don't need the gears. My old truck which had 375rwhp 4.1 diff and Patrol manualised auto (sort of!), would change and it made no difference to acceleration. The big thing with manual auto is you never need to take your foot of the gas so they just keep going. My truck had 1800rpm stall TC and as long as it was over about 2500 rpm it would haul! So shifting at 5 to 6000rpm and dropping 2000rpm each shift was really irrelevant.
For offroad I just don't see the need for more than 4 gears, unless you are talking about peaky high boost turbo motor that is.

[bazooked]

its got me farked were they get these prices from, there is alot of guys around that promise the goods in a box here in aus and dont deliever, seen it alot, personally id stick with a built 400, at the end of the day there is less that can go wrong with it.

[Slunnie]

Does anyone know a supplier where I can get a 2wd 6l90 (stronger 6l80)
I think they are in a chev 2500 or similar.

Bru, maybe try direct? I'm not sure if anything in Aus came with that tranny????

[raptorthumper]

Bru,

the torque ratings are for 1:1 so if you use a 6 speed then the max rating is reduced once in overdrive. (Just like the age old drama of towing in 5th gear in a manual) so if 6th is 0.667 you have to consider the box will 'reliably' only handle 2/3 of the rated torque (give or take a little bit).

This is incorrect. The 6 speed automatics are nested planetary gears and are rated to full engine torque, except in the lower gears, where the output torque is reduced using TM (Torque management). Gearbox output torque is rated to 900 N-m for 6L80e or 1200 N-m for the 6L90e.


http://archives.media.gm.com/us/powertr ... _MYC_n.xls


http://archives.media.gm.com/us/powertr ... _MYD_n.xls

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