Have a 3 speed 400 trans, want a 4 speed 400? Help?

[1LOW4X4]

Guys, I have an 85 silverado 3/4 ton, 350/400/4.10. Automatic trans.

This thing runs 3000 Rpms at 65 mph. Unacceptable.

Is there a 4 speed version of the 400? I need one bad!

Thanks fellas

Pic of the truck

[75gmc454]

Nice truck. You are looking for a 4L80-E. It is a 4 speed heavy duty trans like the 400. It is an electronic trans, so you will have to have a trans computer to run it.

[1LOW4X4]

You mean the 4L80e that came in the 99 and up hd trucks?

Isnt the bolt pattern different from a 350 to a 6.0 ls based motor?

Sorry all the questions, just trying to grasp this. If this is the trans you speak of, where and how does the computer hook up?
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[cableguy0]

The 4l80e came into use in the early 90's. Its still in use now as the heavy duty auto trans for gm. You will need a standalone controller which is about 1000 bucks plus you will need the transmission itself. Transmissions are interchangeable between the ls and 1st gen sbc engines. If you use your truck as a truck the more readily available 4l60e or 700r4 is not a good option. Its nowhere near as strong as the th400 or 4l80e

[benoit454]

you want an od trans 700r4 4l60 4l60e or 4l80, the 80 is supposed to be like a th400 but with overdrive but it's computer controlled same as the 50e from what I've heard.

You could swap rear ends or gears if you wanted to. it would lower the rpms and save some gas, but you'd loose some low end grunt.

[1LOW4X4]

Yeah I know all about the weakness of the 4L60e.

Man I was hoping that they made a 4 speed version of the 400, non electronic lol. No way I'm gonna buy a 4L80 and a thousand dollar controller for this thing.

Hell, I'm saving up to buy an FLT level 7 trans for my '01 to hold the power, no way I can afford a 4L80e for this thing. Thanks for the help guys
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[BigBlocksRule]

I bought a used controller last year for $300. Sent it to Accel, tested fine. I NEED a 4L80E, my project is a pump gas 565 truck, badged to look like a 454SS. I haven't given more than $250 for any of my 4L80E cores, but the rebuild kits are high - around $300 for a basic kit. Once finished, a stock 4L80E is rated at 800 ft/lbs.
A later model 700R4 can be built to take everything your 350 can throw at it for not a lot of money. When looking at one, you want the one with the case that has a casting line running right through the coolant bosses, it's the better case, should be '89 - '92 or so. Upgrade to a 10-vane pump and hardened sun shell and you should be fine.

[fattyarbuckle]

get one of these.

http://www.gearvendors.com/cg2wd3s.html

[BigBlocksRule]

$2800 plus installation just to go OD? It's a lot cheaper to run a 4L80E - or scavenge a complete running engine and tranny, harness and all, and convert the truck to EFI at the same time.

[Pop's C-10]

A well built 700 should do you fine...

[ironroad9c1]

There is no 4L80 only the 4l80E Don't get that confused with the 4L60 (AKA still a 700r4 with a new name ) and the 4L60E which is the full electronic 700R4 there is only the 400 and the 4L80E

[Dalaigh]

What do you do with your truck? You could swap gears from 4.10 to 3.73, it's a cheaper alternative to swaping the trans. and will net you some better gas mileage and lower your rpm. If your tires are about 31" tall then 3.73 should put you around 2600rpm.

[1LOW4X4]

I don't know where y'all live but around here a good condition 4L80e is expensive.

Also, there's no way I'm going to convert this truck to an all ls drivetrain and engine. Part of the fun in driving these old trucks is driving them with the carb'd engines they came with. I already have 3 NBS vehicles so I don't need another 5.3 in the truck. I just rebuilt this 350 in this truck.

The tires are tall as hell. I'll measure them, a gear swap might be in order. I don't tow or pull very often but when I do I need it to work.
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[Dalaigh]

I had 3.73's in my old 97 heavy half and I towed a 30' Sailboat twice a year, about 25kms each time, with out a problem. If your only towing a few times I can't see 3.73's or even 3.42's being a problem. Infact I've got 3.42's in my 84 3/4 with 35's and it still boogies pretty good, however my gas mileage sucks because of the tires, I need 4.10's or even 4.56's.

[1LOW4X4]

Originally Posted by Dalaigh

I had 3.73's in my old 97 heavy half and I towed a 30' Sailboat twice a year, about 25kms each time, with out a problem. If your only towing a few times I can't see 3.73's or even 3.42's being a problem. Infact I've got 3.42's in my 84 3/4 with 35's and it still boogies pretty good, however my gas mileage sucks because of the tires, I need 4.10's or even 4.56's.

I used to tow a lot with my 01 before I lowered it and it had 3:73's. Did great.

I just hate to lose the 4.10 on this truck, it came on t for a reason I guess.

But I cant see 3000 rpm at 65. That's too much.
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[Dalaigh]

Originally Posted by 1LOW4X4

I used to tow a lot with my 01 before I lowered it and it had 3:73's. Did great.

I just hate to lose the 4.10 on this truck, it came on t for a reason I guess.

But I cant see 3000 rpm at 65. That's too much.
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Well the 4.10's came in most camper specials, because of the wieght of a camper in the back and what ever it was towing. The gears help quite a bit, but I would think to get the rpms in a better range, 3.73's would work, plus if the old gears are still in good shape you could keep them and swap them back if your use for the truck ever changes.

[mooseknuckles]

def. swap out the 4:10 gears, then the 400 for a 700r4.

[Dalaigh]

BTW thats a nice clean truck

[1LOW4X4]

Originally Posted by Dalaigh

BTW thats a nice clean truck

Thanks, I've never seen one in such good original condition. Now wear on anything in the interior. It's really like brand new inside. No rust, California truck.

Bought it for 800 with a spun bearing. Replaced everything under the hood and rebuilt motor. All new ac lines and components, blows strong and cold. It's a camper special, but I did away with the sliding back glass and added a solid.

It is a pleasure to drive this truck, I only wish it was 4x4.
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[Aegeas]

I believe the 4L80E is also longer than a normal TH400. That would mean drive shaft issues to be rectified.