73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Skunksmash on June 16, 2009, 03:08:21 pm
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It seems that my truck has a 700R4 in it. Some people seem to despise this transmission for some reason. Mine's been rebuilt as it was leaking when i bought the truck. I like it for the simple reason that it has a 4rth gear for the highway. I can remember in my 81, it had some lousy 3 speed auto in it. And at 65 mph it sounded like i was about to take flight or something. And as such the MPG went down the toilet. I know a lot of you guys here think that people who want more MPG are somehow like pansies or something, but sorry, I'm not rich. Saving money is smart. So here's my questions:
1. Why do people hate the 700R4 so much? Any tranny will die if you treat it like crap...
2. If a person wanted to replace their 700R4 with a newer better model 4 speed, which factory GM tranny should be used?
3. Is there a 5 speed automatic tranny that would work in one of these old trucks? Just curious. Back to the whole MPG thing.
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I am not a fan of any automatic in a truck but that is probably just me. I think 700R4's get a bad rap because of when they first came out. They where usually paired with a highway gear and had a hard time deciding what gear to be in at cruising speed unless you are doing 80. All the appropriate upgrades and a knowledgable trans guy that has the tools to properly adjust them is what is needed IMO. I am sure Vile can give some insight as well. My $.02
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The 700R4 is a good trans.
No one is against getting better fuel mileage however if you're looking for an economical ride these trucks aren't them.
The 4L80E is the strongest 4 speed auto drop in available however you need a standalone computer or the factory harness and computer from the donor along with the appropriate sensors.
If you really want more gears http://6l80e.com/
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hmm whats the origin of the 4l80e? When did they start using them and what is the most desirable year to have one out of? I guess if they still make it, then the current year huh.
And what does the 6l80e typically come in? That is a little overkill lol. I was thinking of a 5l80e. Probly doesn't exist. But something that could be found in a junkyard.
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The 4l80 is basically a TH-400 with OD. I believe they started either in 90 or 91. If you can get one that is 97 or newer it has all the factory improvements over the originals, but it does not take much to get the earlier ones up to par. With a transgo 2 shift kit, they are capable of handling 800hp. There is a kit to make them into a manual shift, but there are controllers for them to let them be electronically controlled. TCI makes one, and BS3 has an optional controller with their standalone engine management setup.
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I believe they started either in 90 or 91
My 91 V2500 4x4 sub has the 4L80E and it has 202,000 miles on it and runs like new. I don't think there is anything wrong with the early 4L80E's. Of course, I put an external cooler on it the instant I bought it.
I had a problem with one of the VSS sensor wires being stripped, but, I insulated the wires again to the sensor and she runs as good as ever.
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Think they are more parasitic than a 700R4? Typically, stuff that is tougher is harder to turn and sucks down more power. You know how you lose roughly 70hp from the flywheel to the real wheels? Think of the Ford 9" rearend. A lot tougher, and a lot harder to turn than smaller weaker ones. Something for me to consider, since i only intend to pull a bass boat, (and other small trailer tasks) with my truck. After all it's only a 1/2 ton.
Besides the price, the 6l80e looks nice if it isn't something that goes in a dumptruck. If you had a 6-speed, you could have the best of both worlds. You could have like 4.88's as your rear end gear ratio, and still be running 1900 RPM's at 75 Mph on the highway. Maybe that's not exact but you get the idea.
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Yes the 80 will have more loss than a 700r4. How much power do you plan on putting to the transmission? And what are your intended usage for the truck. That will determine what you need, not what you want.
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Low Hp compared to most of the guys here. Probly around 320-350. Not real sure how it will turn out just yet. Slightly higher torque than that, im sure. I want to be able to do all the fun truck stuff with it like towing boats and jet ski's and light hauling and such. And i want to get somewhat close to the factory MPG, which was like 17-20. Cant do that with 480hp and a tranny/rearend on steroids lol
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Yes you can...
As long as you have something else to drive. ;D
FWIW, I've got a Ranger I drive most of the time, the Chevy is for the more serious work.
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Well, with a 91 sub, 4x4 on a 3/4 ton chasis with a 4l80e, I have gotten 17 mpg on the interstate with a 5.7 that has 200k miles. And, that is with the family on board. Going to the outer banks of N.C. 4th of July weekend, about 5 hrs away to Cape Hatteras, gonna check my mileage again then.
I dont loose too much through the drivetrain i dont guess, because the 350 has little problem pulling my 30' camper trailer over the Blue Ridge Mountains.
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Cool. So a pontoon boat should be no problem. Nice to know. The only pulling i have done has all been with Ford F-350's, and they can tow off with your house if you want to. So i was kinda wondering about a gasoline 5.7L.
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a lot has to do with the rear ratio and wheel size. I have a 3.73 rear with 33's on it. Not too low, not too high.
I saw on craigslist a set of 4.56 gears that came out of a sub and got me thinking about that, I could rip off the line so quickly with those puppies and that COULD then pull a house. And with a 4l80e, the highway driving wouldn't be too terribly bad due to the lock up torque converter and overdrive. So, it got me thinking.
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Well my gears are 2:73's. :D And i have the stock 15" rims and appropriately fitting tires. So i am hoping that will suffice. If not then oh well, i'll order one of those 700R4's from that monster 700R4 website. i was just thinking it would be real nice to have one more gear for the highway.
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it would be real nice to have one more gear for the highway
you will have plenty gear for the highway with 2.73 rear....that is a high rear, therefore very low rpm's on interstate. If you put an overdirve on a 2.73 rear, the OD will probably kick in around 70mph--may be exagerating a little, but, you will have great speed with little rpms from the engine. Top speed should be around 300mph. ;D
A 2.73 is a high gear for pulling, but, if it isn't a heavy load, it should not be a problem.
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My factory gearing was 2.73 with a 700R4. My opinion was that this actually hurt gas mileage. The reason being the engine was bogged down on all but perfectly level highway and if you encountered any type of steep grade a downshift to third (sometimes even second) was needed to maintain speed (forget accelerating). Somewhere along the road, I got this hair-brained idea that 3.08s would help with this while still maintaining low rpms for economy. Wrong, that was a colossal waste of money. Now with 3.73s I can accelerate with ease in fourth at highway speeds. My mpg has improved (over the 3.08s) at speeds of 55-65 and remained about the same at 65+. I'm sure there is a trade off point at about 85 mph where the 3.08s would be better for mpg, but I don't cruise that fast, and frankly if you are worried about mpg you should be cruising no more than 60 anyways.
In conclusion, 2.73s are a great economy gear for TH350s, but not for 700R4s. I would run no less than 3.42s behind a 700R4.
Top speed should be around 300mph. ;D
On the other hand, just think of how much time could be saved traveling around at 300 mph.
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so true. you have to take advantage of the preferred rpm the engine wants to go. With a high gear 2.73, the engine rpms are just too low for any power or fuel efficiency (if you have to push the accelerator all the time to maintain speed).
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So yall would recommend that i change the gear ratio to 3:42's? What RPM should that put me at, if i am traveling at 70mph? It is nice to be able to use the fast lane on the highway. And i do some highway traveling sometimes. Seems strange that your 3:08's didn't work out the way you wanted. And to be honest, the truck burns out too easy as it is lol. (spins tires on takeoff)
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(3.42 x 70 x .70 x 336) / 28 = 2011 rpm
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^ Is that formula assuming 28" tall tires?
Skunk, I'm in the same boat as you right now. I'm trying to determine if I should swap my perfectly fine TH350 for a 700R4. It seems it's entirely dependent on the trans builder and installer as to whether or not the 700R4 will hold up. I haven't determined yet if the person that I found selling a 'built' 700R4 I can trust or not as building a strong trans. I should get some references from him. Anyway, I have a 3.40 12 bolt in my truck and 27" tall tires. At 70 MPH, I'm turning 3000 RPM and I'm not entirely comfortable with that for longevity reasons. Using Event's formula and 27" tall tires, I should get 2073 RPM. My TH350 doesn't have a lock up converter though and that adds 2-300 or so RPM too.
Ideally, I'd prefer to have a 700R4 I don't have to worry about and a 3.73 rear end and a functioning limited slip. That's another $1000 away though.
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And to be honest, the truck burns out too easy as it is lol. (spins tires on takeoff)
if your truck burns out easily with 2.73 rear, man, with a lower gear, you better have a few sets of tires on standby.
So yall would recommend that i change the gear ratio to 3:42's? What RPM should that put me at, if i am traveling at 70mph?
depends if you have overdrive or not. She'll be tacking quite a bit more but you'll be able to pass others easily just by practically thinking about it. That's a better rear for towing--you'll have power to actually go over hills without flooring the accelerator. If you do a lot of city driving, 2.72 gears just are too tall, you have to keep your accelerator down just to get the truck going. I think you mpg will increase with something like a 3.42 or 3.73
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^ Is that formula assuming 28" tall tires?
Yes.
[rear gear] x [speed in mph] x [trans gear] x [constant] / [tire diameter in inches] = [RPM]
*Assumes manual trans or locked up converter.
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Just to add a lil more to talk about- what about the addition of an aftermarket overdrive unit, like GearVendors or similar? What're the pros and cons for Skunkmash ( other than costing about $1300).
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Whoa, i did not even know those existed. They are like $2950 lol. I guess they sort of add another gear, in a way?
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Pros: Gear splitting for drag strip performance, OD gear, durability, keep your current trans.
Cons: $$$, no TC lockup, keep your current trans.
Unless you feel you could benefit from gear splitting, I'd just build a 700R4 or 200R4.
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More on the mpg thing:
My personal belief is---and we ARE going to split hairs here but so be it, is i think a higher diff ratio with direct drive trans (1:1) will get better mpg than an overdrive transmission with a lower diff gear. i feel this way because it takes more energy to drive and OD trans vs. direct drive.
i run a TH-350C and 2.56 gears and get 15.8 for a low and 17.20 for a high, so let's just say average 15.8mpg just to rate it conservatively. This is with scientific testing. And this is with 350 cubes.
You've got 2.73's, so you're looking good in that department.
2) The 700 is simply a more versatile transmission; i can't argue against that. If you want more responsiveness/acceleration/better performance, this is your trans.
3)The energy consumption difference between the two may be negligible, but i still feel there is a difference in economy. Possibly a small one, but a difference nevertheless.
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On the highway, all other things equal, a TH350C with 2.56's will get about the same mpg as a 700R4 with 3.73's. The major differences come in when you throw around town mileage into the mix. A 700R4 has 11.41:1 total gearing in 1st and 6.08 in 2nd with 3.73's, while a TH350 has 6.45:1 in 1st and 3.89:1 in 2nd with 2.56's. When setup with these respective rear gear ratios, in normal driving, the 700R4 will require much less throttle to accelerate than the TH350, given the same acceleration rate. Under aggressive driving situations, the 700R4 will accelerate much faster.
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Stewart 3rd gear in most transmissions is direct drive.
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Maybe i missed something... but is the 4rth gear in a 700R4 direct drive?
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overdrive
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Like Vile said- almost all the trannies have a 1.00:1 third gear. Here's a page from Bowtie overdrives- great tranny site!
http://700r4.com/faq/gearrat.shtml (http://700r4.com/faq/gearrat.shtml)
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What i meant was max mpg in cruise mode; Yes, we could put the 700r/2004r in 3rd while we cruise at 55-65 and we'd be in direct drive, BUT, with the lower diff gear--say 3.73, 4.11 etc., we would be rpming rather high. i still feel that a TH-350c with 2.56 gears will deliver slightly better mpg all other factors equal.
The 700/200R4 might(probably) give better mpg in city.
Yes, we are splitting hairs here, but maybe we should be splitting hairs.
Actually, i will get into deeper detail but cannot now due to being physically incapcitated---overworked. Must rest.
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Stewerat, I'm not really following your logic here.
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i'm basically as far as mpg goes talking about highway cruising where i feel most of us, myself at least, spend most of our driving.
When i personally do 65, i'm turning 2100 rpm with my setup. i am in third gear and top gear when this is occuring because i have a TH-350C. And, this of course, is direct drive (1:1) as we've established.
Now, if in another example we have the/a same truck except equipped with a 700R and say 3.73 gears AND depending on tire size we are able to ALSO turn 2100 rpm at 65 miles per hour i feel that the above setup will achieve better mpg. This is due to the fact that in this second setup, we are in overdrive which takes a little bit more power to turn than direct drive-----.70 to 1 vs. 1 to 1.
In both examples, we are traveling at 65 miles per hour with the engine turning at 2100 rpms. But one is taking a little less energy to operate.
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it is true the less you have to press your accelerator to maintain a certain rpm or speed, you will save that much gas.
The question becomes, does overdrive require more "power" therefore accelerator action to maint 2100 rpms? I wouldn't think so, or, your accelertor action will knock it out of OD
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Actually, after this post i resign from the discussion----because explaining it itself is requiring more energy than nessesary.
i don't think it would kick out of OD if it takes more energy than direct drive; i believe there is a predetermined setting at the TV cable (if the 700 uses one) or by some other means.
So, nevermind; Let's not worry about it. Since the difference is probably pretty small.
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You will not be in overdrive if the transmission is functioining correctly if you require torque multiplication as there is a torque decrease and speed increase. In 3rd gear the 700R4 is the same as the 350C except you have the addition of 4th giving you overdrive.
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Anyone happen to know what all cars came with the 6l80e? I know the 2006 Cadillac STS-V did, and the new vettes do. They are not really all that expensive, as tranny's go. $3000 newly rebuilt according to google. I had to give half that just for my 700R4. But i was thinking maybe some junkyard find might work. Hopefully it's getting common by now. Also, would it be hard to mate it up to an old TBI motor like mine? What all would be involved in that?
Here are the ratios of a 700R4, and a 6L80e.
Gear Ratios: for 6l80e
1st: 4.02
2nd: 2.36
3rd: 1.53
4th: 1.15
5th: 0.85
6th: 0.67
700R4 Ratios:
1st: 3.06:1
2nd: 1.63:1
3rd: 1.00:1
4th: .70:1
Maybe you could have the transmission guy change the 6th gear in the 6l80 to be something like .50 or something? That way, you could run 4.55's and have the best of both worlds? (maybe that's the wrong numbers on that last ratio, but you know)
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2 OD gears, wow.
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Yeah but look at 'em. They suck. At the end, they don't put you any better off than a 700R4. You would need to have the transmission man set the 5th gear to like .50, and the 6th to like .34 to have it be worthwhile.
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Well, with a 91 sub, 4x4 on a 3/4 ton chasis with a 4l80e, I have gotten 17 mpg on the interstate with a 5.7 that has 200k miles. And, that is with the family on board. Going to the outer banks of N.C. 4th of July weekend, about 5 hrs away to Cape Hatteras, gonna check my mileage again then.
I dont loose too much through the drivetrain i dont guess, because the 350 has little problem pulling my 30' camper trailer over the Blue Ridge Mountains.
And when might we be able to expect your second installment of the almighty 383 stroker into said suburban? Bet it pulls the camper just fine with one of those.
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And when might we be able to expect your second installment of the almighty 383 stroker into said suburban? Bet it pulls the camper just fine with one of those
with the 383 in my 79, I have no problem pulling the camper. With the sub's 5.7, on the longest, steepest part going over the Blue Ridge, I have to put it in L2. I have 200k on the 5.7, so, whenever she does go, which may be a while from now because it still doesnt use any oil and runs great, I will rebuild it with a 400 crank, no doubt. I just hope it doesnt mess my computer up on the sub.
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you know, it's too bad we don't all live in the same state. We could all have some kind of get together where we bring our trucks and show em off.
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You can't have a transmission shop "change" the final drive on the 6L80E, you also don't want to drop the OD ratio any lower.
You could run 4.56's in the 700R4 and it would be like 3.23's in OD and you wouldn't need a $3000+ controller to operate it.
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I have an 85 K-10 with the same HP or slightly more. My setup is a 700R4 with 3.73 rear and 31" tires. I tow a 5000lb boat and the setup seems to work very good for me. I don't use OD when towing though. I just got the 700R4 working good (TV cable issues separate topic) and I really like it. The 700R4 will give you the "fuel efficient flavor" for less money than a later model tranny IMO.
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You can't have a transmission shop "change" the final drive on the 6L80E, you also don't want to drop the OD ratio any lower.
You could run 4.56's in the 700R4 and it would be like 3.23's in OD and you wouldn't need a $3000+ controller to operate it.
If i had an RPM gauge i could see what i would be happy with. But of course they decided to leave that out for some reason.
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If i had an RPM gauge i could see what i would be happy with. But of course they decided to leave that out for some reason.
Buy a cheapie, wire it up, and zip tie it to the steering column. That's what I did. ;)
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How hard is that? I never can get a straight answer on what all is involved. I mean, where do you run the wire to?
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Usually
Green goes to the Distributor (Cant recall what its marked but you will know it should be the only one not connected)
Red Ign 12v
Black Ground
White instrument circuit.
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the distributor wire as mentioned is green, and the HEI caps are labelled accordingly..."TACH".
it can't get any easier than that. All tachs have instructions, as mentioned red to ignition source 12v, white to headlight switch or instrument cluster for backlight, black ground as always.
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Gear Ratios: for 6l80e
1st: 4.02
2nd: 2.36
3rd: 1.53
4th: 1.15
5th: 0.85
6th: 0.67
Thought of another question. Just because these are listed as the factory gear ratios on the 6L80e, does that mean that it is set in stone that those are the ratios that i would get if i went to the junkyard and bought one? Maybe they are different from car to car. Maybe the vette 6l80e has different ratios than the one that they put in the cadillac? Anyone know? The caddy is luxury, the vette is performance. So it stands to reason the vette that they might want to gear the vette differently.
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4.02:1 first gear. Hoo boy, almost like a tranny with a granny gear!
Yep, putting in a tach is easy. Says 'TACH' right on the HEI cap. You will see two tabs there. One says TACH. Put a female spade connector on the end of the green wire and shove it in there. Wire up power (red) to an open spot in the fuse box (on the fused side of an accessory switched location) and ground it. White wire to the headlight switch is about the hardest part, and it's only hard to determine under the dash which wire you tap into and how accessible it is. Mine is still unconnected.
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All Automatic transmissions of the same type are geared the same the only thing that changes from car to car is the final drive ration.
If you go get ANY 6L80E the ratio listed IS the ratio of all of them, period. You can't change it and they are selected by the manufacturer to be the best optimium ratio for the target application.
Same thing goes for any factory manual or automatic transmission ration. You get what you get and that is it.
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Well the T-56 tremec had different ratios for different cars. Some got a .63 6th gear, some got a .50.
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All Automatic transmissions of the same type are geared the same the only thing that changes from car to car is the final drive ration.
Well the T-56 tremec had different ratios for different cars. Some got a .63 6th gear, some got a .50.
The Tremec T-56 is a standard trans.