Trans swap from T400 to Overdrive

[Eyegore]

OK this is transmissions for dummys, me being the dummy. If I want to change the exisitng T400 to a overdrive unit, whatever the 4l80 is, but without a computer to run it and w/o changing tailshaft and cutting down the driveline but only changing the selector to in OD, can it be done? And what is the most inexspensive way to do it and what year of tranrmission should I be looking for?
This is for a 82 3/4 ton w/ 6.2 diesel

Tom

[jimbonice]

Well, I believe the 4l80e requires the 'puter to run, either factory or aftermarket. I don't believe 6.2's ever came with the 4l80, but 6.5's did in the early '90's squares and had a stand alone computer for the trans. Not much getting around that. I know they make full manual valve bodies for competition; I don't know how street friendly they are and shifting the transmission may get tedious after a couple thousand times

And that brings up the much maligned 700r4, which would be the cheapest o\d swap. No computer needed, can be mildly modded to live in a truck - I've had on in my 454 C30 dually for 30,000 miles - and has a great first gear with a low 3.06 ratio compared to a 2.48 for just about everything else. A 6.2 would not be any harder on it than a 454 in a crew cab dually. It makes pulling the boat out of the water much easier, as well as taking off with a camper on the back. With my 4:10's it makes an effective 1st gear ratio of 12.5 to 1. In a 4l80e it would take a rear gear of 5 to 1 to match it.

You'll end up doing driveshaft mods irregardless of what is swapped, so plan for it. It is not necessary to change the selector as the detents in the transmission determine where the selector pin end up.

Maybe someone else will chime in here, but an o\d trans is no guarantee of better economy in these full size trucks and may never pay back the cost of the swap. In the 6.2's, lugging along out of the powerband in overdrive might return the same or worse economy. If you tow or work your truck alot of the time, I'd be tempted to leave the t400 in, because you won't be using o\d anyways.

good luck with your decision.

[Edahall]

Originally Posted by jimbonice

Maybe someone else will chime in here, but an o\d trans is no guarantee of better economy in these full size trucks and may never pay back the cost of the swap. In the 6.2's, lugging along out of the powerband in overdrive might return the same or worse economy. If you tow or work your truck alot of the time, I'd be tempted to leave the t400 in, because you won't be using o\d anyways.

good luck with your decision.

My experience with these engines has been that keeping the RPM's down definitely gives better economy. For best results on these engines, you want to cruise right around 1800 rpm's where the torque curve is at its highest. My 1982 Suburban has a 700R4 over drive transmission and I'm running a 3.08 rear end. This truck returns 30 mpg on the freeway driving conservatively. However, I don't like the 700R4 transmission. It is way too weak behind this engine even with all the mods. I've dumped way too much money into transmissions for this vehicle. For my latest Suburban, I switched over to a NV5600 manual transmission and could not be happier.

Eyegore,
Since you're looking for inexpensive solutions, here's my recommendation. Keep the TH400 but install the lowest stall torque converter you can find. The low stall converter will keep the slipping to a minimum and transfer more power to the ground which will give you better fuel economy. Is your truck 2 wheel drive, 3/4 ton? If so, find a 3.08 rear end out of a 1st generation 3/4 ton Dodge truck. Afterwards, get some 235/85/16 tires. These tires are large diameter and will bring your rpm's down. The above setup I mentioned will bring your RPM's down just a tad under 2000 rpm's at 60 rpm which isn't too bad.

[veinbar]

Originally Posted by Edahall

My 1982 Suburban has a 700R4 over drive transmission and I'm running a 3.08 rear end. This truck returns 30 mpg on the freeway driving conservatively.

Is this a typo? What engine / transmission are you running? I need to swap to whatever you have.

[Eyegore]

Originally Posted by veinbar

Is this a typo? What engine / transmission are you running? I need to swap to whatever you have.

No typo the 82 6.2 diesel I have gets 18 mpg in town, that is why I am looking into the overdrive to bump it up to 30 ish like mentioned but stout enough to do some heavier hauling though the 6.2 was not made for heavy hauling

[Edahall]

Originally Posted by veinbar

Is this a typo? What engine / transmission are you running? I need to swap to whatever you have.

Originally Posted by Eyegore

No typo the 82 6.2 diesel I have gets 18 mpg in town, that is why I am looking into the overdrive to bump it up to 30 ish like mentioned but stout enough to do some heavier hauling though the 6.2 was not made for heavy hauling

It's not a typo. The 6.2 diesel, can get very good fuel economy if equipped correctly and geared correctly. The earlier 6.2 diesel versions got better fuel economy than the newer versions because the heads had larger valves and smaller precombusion chambers. The smaller precombustion chambers limited power output but maximized fuel economy. The later 6.2's with larger precombustion chambers can be fitted with smaller precombustion chambers to maximize fuel economy but power will be reduced. When I first got my 1982 Suburban, it got mid 20's on the highway and didn't have much performance. So I made some mods that increased power and economy.
1. Exhaust headers
2. Free flowing dual 2-1/2" free flowing exhaust with H pipe.
3. J code intake manifold (no EGR)
4. Ported the heads
5. Gear Drive for camshaft
6. Advanced the timing

If you do a lot of high speed driving, another mod that helps out a lot with mpg's is a lowering kit. I haven't done this to my Suburban so if I drive 80 mph here in TX, gas mileage goes down.

Eyegore,
If you're looking for a transmission that has an overdrive and is stout enough for heavier hauling, look for a NV4500 manual transmission. It'll set you back about $1k for the tranny and you have drive line changes to make. However, you can also do what I mentioned in a previous post and probably get very close to spending the money for a different transmission.

[veinbar]

Originally Posted by Eyegore

No typo the 82 6.2 diesel I have gets 18 mpg in town, that is why I am looking into the overdrive to bump it up to 30 ish like mentioned but stout enough to do some heavier hauling though the 6.2 was not made for heavy hauling

That's insane... I had no idea we were dealing with a diesel in this scenario, which I know can turn impressive numbers. This forum makes it difficult to daydream sometimes... There are too many "dream" drive line combinations to choose just one. Thank you for explaining.

[jimbonice]

Originally Posted by Eyegore

No typo the 82 6.2 diesel I have gets 18 mpg in town, that is why I am looking into the overdrive to bump it up to 30 ish like mentioned but stout enough to do some heavier hauling though the 6.2 was not made for heavy hauling

What is your description of "heavy hauling"? It makes some difference on what trans you're looking for. My heaving hauling is 10,000 lbs, for some people it is 3000 lbs, for others it is 15,000 lbs. Also, you're rear gear is going is going to come into the picture as well. Irrespective of what transmission you choose you will need a compatible rear gear. 10,000lb loads are going to require steep gears, like 4:10's or maybe 3.73's to keep the 6.2 happy in 3rd gear on the highway. If you have 3.08's in the back, then I don't see heavy hauling in your 6.2's future without a gear swap.

[rruss86]

Originally Posted by Edahall

My experience with these engines has been that keeping the RPM's down definitely gives better economy. For best results on these engines, you want to cruise right around 1800 rpm's where the torque curve is at its highest. My 1982 Suburban has a 700R4 over drive transmission and I'm running a 3.08 rear end. This truck returns 30 mpg on the freeway driving conservatively. However, I don't like the 700R4 transmission. It is way too weak behind this engine even with all the mods. I've dumped way too much money into transmissions for this vehicle. For my latest Suburban, I switched over to a NV5600 manual transmission and could not be happier.

Eyegore,
Since you're looking for inexpensive solutions, here's my recommendation. Keep the TH400 but install the lowest stall torque converter you can find. The low stall converter will keep the slipping to a minimum and transfer more power to the ground which will give you better fuel economy. Is your truck 2 wheel drive, 3/4 ton? If so, find a 3.08 rear end out of a 1st generation 3/4 ton Dodge truck. Afterwards, get some 235/85/16 tires. These tires are large diameter and will bring your rpm's down. The above setup I mentioned will bring your RPM's down just a tad under 2000 rpm's at 60 rpm which isn't too bad.

ok so i have a 1987 suburban 3/4 400 trans with 4.10 gears. i am in truckin so my burban only goes to shows and drag fests.. i have a 29" tire. what gears can i run to get better mpg...

[Edahall]

Originally Posted by rruss86

ok so i have a 1987 suburban 3/4 400 trans with 4.10 gears. i am in truckin so my burban only goes to shows and drag fests.. i have a 29" tire. what gears can i run to get better mpg...

The gears for best fuel economy with your setup would be 3.08's. However, good luck finding a 3/4 ton 3.08 axle. The only truck I know that came with it were the 88-90 Dodge with the Cummins engine.

Another idea is installing a Gear Vendors OD unit. They're pricey but with the price of fuel these days, it might not take long to pay it off.

For best fuel economy, go with a 700R4 transmission and 3.73 gears. The downside is the 700R4 is not nearly as robust as the 400 transmission especially when it comes to heavy towing.

[rruss86]

Originally Posted by Edahall

The gears for best fuel economy with your setup would be 3.08's. However, good luck finding a 3/4 ton 3.08 axle. The only truck I know that came with it were the 88-90 Dodge with the Cummins engine.

Another idea is installing a Gear Vendors OD unit. They're pricey but with the price of fuel these days, it might not take long to pay it off.

For best fuel economy, go with a 700R4 transmission and 3.73 gears. The downside is the 700R4 is not nearly as robust as the 400 transmission especially when it comes to heavy towing.

ok so can I just re gear my rearend with a 3.08.... it won't ever pull again.
Posted via Mobile Device

[hatzie]

The Optishift computer should work. I like the level of detail provided in the manual.
You'll need to install TPS on your carburetor.
You'll need to work out the speedo cable. The 4L80E is setup for VSS only.

[nekkidhillbilly]

easiest would be find a 91 truck and swap in the 4l80e and its controller. 700 will work but its not very stout. however before id spend a grand on a nv4500 i think id find a used 80e and buy a controller be about the same money. most t400 trucks have 4:10s which is perfect for the 80 also. i doubt you will see big mpg on a diesel until your on the highway however.

[Rogier]

Oh by the way: don't forget the flywheel. I had to replace some of the parts there to make it bolt up to the bellhouse. Nothing that is hard to acquire, but I don't know all the names of the parts. I Just replaced it comparing it to an engine that originally had a 4L80e connected.

[DetroitDan]

Very interested, I have a th400 behind a 454 and I hate it. I've been told the 700r4 is totally fine for a stock or mild 454, and I've also been told the 700r4 is going to explode the instant you put it into gear for the first time. I don't know who to believe. But, putting the 700 in will require moving the t-case back, shortening the rear driveshaft and lengthening the front. Then if I do break the trans, I can only replace it with another 700. I'd be tempted to do it, using a big auxiliary cooler with an electric fan and a temp gauge, like I always did on my plowtrucks. But, leery because I am going to tow 10,000 and I am not known for being gentle with trucks.

I like the 4l80e a lot, had one in my 97 diesel and whipped it like a rented mule for ten years plowing. Since the 4l80e is built on a 400, aren't the dimensions going to be the same? So the driveshafts can stay the same? I can find a 4l80e cheap enough, the controller would be the big expense for me, I'm pretty poor. What I really want to know is what kind of economy gains can be had by swapping to either a 700 or 4l80? I don't want to spend thousands to save hundreds. I hardly even drive the truck, mostly because it is so terrible on fuel, I'd guess I'm getting around 8 mpg around town. And seriously, how good is it going to get? It's still a big thirsty motor, even at idle. I've seen brand new, perfectly tuned carbed 454s with th400s pull down 14 mpg, but I'm lucky to get half that with my lifted truck with a loud pedal. If I could get upwards of 12 mpg, I'd drive it all the time.

[gramps77]

May not be that hard
http://www.summitracing.com/parts/HLY-534-202/
I havent used one but should work if you are carb'd and running a Holley

By the way, I realize you guys are talking about installing the 700 into a truck and possibly towing......as long as you have a large enough cooler for the grades, its not going to "blow up". Ive installed 2 700's and 3 2004Rs (only mentioned since we're talking O/D) but they were all into 63-70 Chevy Novas. some of which though are/were drag raced. As long as you keep the heat from building up, I dont see why you'd need to worry excessively. Get a trans temp gauge installed, monitor it, and if it gets hot, install a bigger cooler.

[Edahall]

Originally Posted by DetroitDan

Very interested, I have a th400 behind a 454 and I hate it. I've been told the 700r4 is totally fine for a stock or mild 454, and I've also been told the 700r4 is going to explode the instant you put it into gear for the first time. I don't know who to believe. But, putting the 700 in will require moving the t-case back, shortening the rear driveshaft and lengthening the front. Then if I do break the trans, I can only replace it with another 700. I'd be tempted to do it, using a big auxiliary cooler with an electric fan and a temp gauge, like I always did on my plowtrucks. But, leery because I am going to tow 10,000 and I am not known for being gentle with trucks.

I like the 4l80e a lot, had one in my 97 diesel and whipped it like a rented mule for ten years plowing. Since the 4l80e is built on a 400, aren't the dimensions going to be the same? So the driveshafts can stay the same? I can find a 4l80e cheap enough, the controller would be the big expense for me, I'm pretty poor. What I really want to know is what kind of economy gains can be had by swapping to either a 700 or 4l80? I don't want to spend thousands to save hundreds. I hardly even drive the truck, mostly because it is so terrible on fuel, I'd guess I'm getting around 8 mpg around town. And seriously, how good is it going to get? It's still a big thirsty motor, even at idle. I've seen brand new, perfectly tuned carbed 454s with th400s pull down 14 mpg, but I'm lucky to get half that with my lifted truck with a loud pedal. If I could get upwards of 12 mpg, I'd drive it all the time.

Don't even consider a 700R4 if you're going be towing that kind of weight with it. Yes you might be able to get by with 5000 lbs and keeping it out of O/D. The 700R4 is very weak in O/D so only use it for solo cruising. You would be better off paying for the fuel than paying for constant rebuilds on the 700R4.

The 4L80E and 400 are different lengths so you'll be into driveline changes there as well.

A different transmission is not going to change your fuel economy around town very much. It's a heavy truck and it takes a lot of energy to get it up to speed.

However, a different transmission with O/D can help your fuel economy on the highway because it lowers your rpm.

A less expensive option that would also give you the ability to tow would be the NV4500 transmission. But you'll have to shift.

Your lift also hurts your fuel economy especially on the highway. Keep your speeds down to 60 mph or less for best fuel economy. I lose 30% fuel economy driving 70 instead of 55 mph.

Take a look at my signature to give you ideas on what it takes to get good fuel economy (in the mid 20's) with these big heavy trucks. It's not cheap though.

[gramps77]

Its all a cost comparison....how often do you plan to tow, how much do you plan to tow, etc...
If you are using your truck and towing as a moving company then yes, you probably wouldnt want to use a 700. Its irritating for the constant blanket statements, not just here but other forums as well, that a tranny will simply blow up or just plain sucks for use at all.
One of the main issues with the 700r4 and towing is a lot of them lock up in OD. If you are towing, you probably wont have it in OD anyways. If the percentage of NOT towing is greater than towing......do some more research before accepting the "its gonna blow up". Everything can reach its design breaking point if you push it hard enough or use it incorrectly. I wouldnt worry towing up to about 5000 with a 700. please see here.....
http://www.gm-diesel.com/vbull/non-t...h-a-700r4.html

[DetroitDan]

see, I've been told not to even consider a 700, and I've been told that the built ones are fine. Obviously I wouldn't two in OD, I didn't use OD towing when I had my 97 4l80e. I would love a 5 speed manual, but it looks like it would be even harder to get all the parts together and make everything work. Plus I dont know which trucks I can swap out of, which ones to avoid, I don't know much at all about hydraulic slaves. But I'd sure like to drive one. I wouldn't consider an sm465, hate those clunky trannies. It's really just a 3 speed anyway, so no improvement over the th400.
So, no thoughts on how much an overdrive auto can help with fuel? I have looked at Gear Vendors, but they won't save you enough to pay for it for years.
I really don't drive on the highway, and the towing is only pulling the camper a handful of times a year. Which is why the 400 is still in there. I even considered swapping the 454 for a 6.2. But diesel is so much higher now it wouldn't be worth it.

Maybe I should start looking at nv4500s... Oh, one other thing, I've got an NP205 transfer case and auto locking hubs. I would love to keep this case in it if I can.

[Edahall]

Originally Posted by DetroitDan

see, I've been told not to even consider a 700, and I've been told that the built ones are fine. Obviously I wouldn't two in OD, I didn't use OD towing when I had my 97 4l80e. I would love a 5 speed manual, but it looks like it would be even harder to get all the parts together and make everything work. Plus I dont know which trucks I can swap out of, which ones to avoid, I don't know much at all about hydraulic slaves. But I'd sure like to drive one. I wouldn't consider an sm465, hate those clunky trannies. It's really just a 3 speed anyway, so no improvement over the th400.
So, no thoughts on how much an overdrive auto can help with fuel? I have looked at Gear Vendors, but they won't save you enough to pay for it for years.
I really don't drive on the highway, and the towing is only pulling the camper a handful of times a year. Which is why the 400 is still in there. I even considered swapping the 454 for a 6.2. But diesel is so much higher now it wouldn't be worth it.

Maybe I should start looking at nv4500s... Oh, one other thing, I've got an NP205 transfer case and auto locking hubs. I would love to keep this case in it if I can.

700R4's work great behind a 500-600 hp light weight car for track use. But I've never see one hold up well towing 10,000 lbs for long distances. If anyone knows where I can buy a 700R4 that is capable of heavy duty towing and not fall apart in less than 70k miles let me know, I'm very interested. I would like to put one behind a 6BT Cummins for another project build.

The NV4500 would probably be the cheapest solution for getting O/D. Find one out of a Chevy 4x4 so it'll fit to your 454.

[beamn7]

Having built a fair share of automatics, here are my 2 cents:
1. THM-700R4 (4L60) built right is a good trans and can last a long time behind a smallblock with up to 450hp and towing no more than 5K lbs OUT of OD.
2. There is no such thing as a 4L80. They all have the "E" at the end and are all electronically controlled. 4L80E is also known as THM-R2 (4 = # of gears. L = longitudinal drive. 80 = series. E = electronic) Example: THM-400 was renamed 3L80 in the late 80's early 90's. 4T60E would be an electronically controlled 4 speed front wheel drive (T= transverse) 60 series.
3. 4L80E is based off the THM400 with the overdrive portion being based off the THM2004R. (2004R is stronger than 700R4)

I'm a fan of both transmissions but for some serious hauling / HP and Torque handling, I'd go with the 4L80E OR a NV4500. Always keep in mind that saying from the old Fram ads: "Pay me now or pay me later"

[78 Chevyrado]

When I was looking for 700r4 for my 78 C20, The trans places I went to asked what I wanted it to do, 400hp, 5200lbs truck tows 8k trailer from time to time, and I dont baby it (unless towing).

They said I need something like a stage 5 or so trans, all the goodies, just not the violent shift.

Also, in a C20 to not have to move the crossmember, to use a 700r4 you'll have to have the tail housing with the mount built into it, its off a 90's caprice police car, dont remember the PN. Otherwise you have to move the crossmember forward, and that will start moving it where the frame curves upward, which wont work.

To put in a 4l80e, the crossmember has to be moves backwards, which isnt a problem, but it may have clearance issues (I've heard) with low hump cab floors.

Here's a site with all the measurements. Look at the "C" measurements.
http://transmissiontechnologies.com/...surements.aspx

As far as the driveshaft, a local shop told me to go from a TH400 to a 700r4, to shorten the driveshaft and install a new front yoke was around $50. So the driveshaft part is pretty cheap and easy, relatively.

[Edahall]

Here's some information on how to go from Automatic --> NV4500
It's a 1st generation Dodge truck with NP205 transfer case so it would be very similar conversion for our trucks. The one difference would be to use an NV4500 out of a Chevy so that it bolts up to our engines. Other than that, it should be very similar.

http://www.dieselbombers.com/1st-gen...onversion.html

[wilkin250r]

I recall seeing a "Heavy-duty/Towing" transmission in a 700R4 configuration from TCI transmissions. It would be pricy, as you're obviously going to be paying more than junkyard prices. But I would imagine it comes with a warrenty.

[DetroitDan]

well now I'm leaning towards wanting to do an NV4500 conversion. I looked around on Craigslist, only found one Chevy nv4500 in my state or neighboring states, and the guy wants a grand for it. A little rich for my blood, I'd pay a few hundred for a used tranny, but not a thousand bucks. I'd rather find a whole truck for a donor, then scrap it and get some money back.
SO...can someone tell me what trucks would be an acceptable donor? I keep hearing Dodge had a lot of nv4500s, but then nothing else is going to bolt up. I'd like to have it as simple as possible ( because I am simple). I did see an early 90s Chevy parts truck with a 5 speed, but it was a half ton, and I didn't know if that was a 4500, or if the half tons had a different, wimpier tranny. I would really like to keep my existing transfer case if at all possible, but if I cant, then I cant.
How about length, is the 4500 longer or shorter than the th400? Can't do much without having to rebuild the front driveshaft, with the 6 inch lift I was told I'd have to lengthen it, but I didn't. It looks fine right now, but I'm sure it won't extend any further to reach if the standard is longer. Maybe the simplest thing would be to swap the trans and transfer together, along with it's crossmember, then just have two new driveshafts built. IDK.