A Tale of Two Transmissions?

[Carl Bice]

Originally Posted by Phobos

Or you could just fix the 400, and drive a little slower and forgo the whole thing!

I think you are right on cue here, as I have already started this habit in my Yukon, They have just recently raised the speed limit here in East Texas to 75 on the highway, and I am making folks mad already, as I drive at 60 already, and where it is set at 60, I slow down to 55, and I have really noticed the fuel savings already, as I have been doing it for over a month now, and even though I am going slower, I am still never late, for anything, and honestly I have nothing that is that Important to get to.. And I have even noticed several people, like to get behind me, and roll slow also. I drive a 40 mile round trip for work, and now I just fill up once a week, where I was doing it twice a week before..Plus I think it helps that I am always wearing my uniform for work, and some mistake me for an off duty police officer? wonder if that makes a difference?

[Phobos]

Originally Posted by Carl Bice

I think you are right on cue here, as I have already started this habit in my Yukon, They have just recently raised the speed limit here in East Texas to 75 on the highway, and I am making folks mad already, as I drive at 60 already, and where it is set at 60, I slow down to 55,

I do the same and my reaction to anyone who complains is....TOUGH!
The left hand lane is for passing slower vehicles.
If you're to lazy to changes lanes to get around me, well, that's not my problem.

Either way, the swap out would be cool and all, but I don't think you're going to gain much in the way of MPG and it's a lot of extra work.
With these beasts, regardless of gear combination, higher speed equates to lower MPG. Anyway, good luck!

[Winnebeater]

I've been debating this for quite a while, but just not ready to jump into the project. I have a 1984 Winnebago Chieftain with a carbureted 454, Bank Power Pack, TH400 with a 4.10 rear end gear ratio and 7.5R16 tires. With this setup I'm sitting at approximately 2500 RPM at 55mph. I've crunched some numbers and by putting in the 700R4 I would get a much lower first gear that would produce a final drive ratio of 12.55:1, that would get the beast moving off the line a little easier and may help my in town mileage ever so slightly. On the highway the final drive ratio would be 2.87:1 versus my current 4.10:1, this would drop my rpm's at 55mph from 2500 to 1750. After looking at the info that Banks has published for my engine this should give me about 395lb.ft. of torque at the rear wheel which is slightly higher than the 380lb.ft. of torque I am getting now at the same speed. My horsepower will drop though from about 185 to 135 RWHP. The other benefit I have in my favor is that my father in law has some experience rebuilding these transmissions and has built a couple with all the necessary things I would need to put it behind an engine capable of 650 lb.ft of torque and 800hp. He's already has a 700R4 laying around to start the build. He built one about six month ago and said he was only into it about $700.

I have also done some research and found that you can install a long tail shaft allowing you to leave the crossmember in its current location and modify the current mounting holes. From what I have read this also allows the use of the current drive shaft by changing the yolk and u-joint that connect the transmission to the forward driveline.

Still having doubts about the advantages though, most of the newer motor homes that have EFI and a OD trans seem to get around 9-10MPG on the highway and I am consistently getting 8MPG on the highway. If I could get 9-9.5MPG then I could justify the swap, but just haven't convinced myself to do it. If I ever do get the nerve up I will post my results for everyone that is interested.

[Carl Bice]

It looks like we have been finding the same information, it looks as though it is doable, but I think , at least for now, we are deciding to just go with what is there, although,I am Starting to look into the Banks options though, but maybe as a later addition, I think we are just going to jump in and just get out there, first, and see where it leads us...A previous post mentioned, that this set up has worked pretty good for almost forty years, so we will give it a few more, and see what happens, After all, it is our first , and somehow, although the DW doesn't see it yet, I think we will most likely be upgrading again anyway...

[Winnebeater]

Originally Posted by Carl Bice

I am Starting to look into the Banks options though, but maybe as a later addition

We were very lucky, our motor home already had the Banks Power Pack on it when we bought it. Our fuel mileage is about the same as our in-laws which is the same chassis and about the same weight, but the power we have over them is incredible. Going from northern California to southern California on a trip last January we had to keep slowing down going up the grapevine so they could keep up with us.

[fleamarketer]

With any tranny you decide,heat is the main bandit to lead to failures.So the biggest tranny cooler mounted away fro the rad is a pm item I suggest you consider.The 700R4's design flaw is it doesn't circulate tranny fluid in O/D well enough and there is another reason why a cooler is critical.It is also a question of what part of the equation you feel is more important being torque vs hp.I can assure you that GM's heads,(nick named the peanut heads)intake runner's cc/valve size hasn't been intended to produce hp,but make to make torque along with the O.E.M. cam.So any gains are in a aftermarket head increase in intake runner cc/decrease in chamber cc-cam and kit.So if torque by it's definition is the amount of work it does is the rating,to move these M/H's wt is more related to torque curve's than HP which happens in the higher rpm ranges.The 454's edge is certain it's size and the potential to produce torque.The 700R4's for their ability of ease of install because of the TV cable are attractive and you can get from TCI valve body for constant pressure so the TV cable isn't as critical.But they really where not designed to haul the kind of wt these M/H's are even when you mod them.The better answer is a 4L80E with a stand alone controller which you can program shift points,how hard those are,and holding it in O/D even going up upgrades.

So now your lowering the rpm with a capable 4L80E O/D tranny and a cooler.You would think because of that a lower mpg would be the result mainly because you not spinning the engine over as fast.Right??.

So here is the 64 million dollar question.Does the volume of gas to produce the torque needed negate the mpg savings.Not the quantity of gas,but the volume of gas.If you where to look at the electronic fuel pumps,there is two very important values.Pressure(the quantity of gas used)and the volume of gas rating.Engines operate on the same basis.

[Winnebeater]

Originally Posted by fleamarketer

The better answer is a 4L80E with a stand alone controller which you can program shift points,how hard those are,and holding it in O/D even going up upgrades.

Only problem with this is that the transmission ($3800) and stand alone controller ($1200) plus the additional upgrades (roughly $500) cost more than the NADA guide on my motorhome. If I had the extra $5500 to make this a viable option I would opt to use it on a down payment into my savings account for the future purchase of a newer motor home that would already have a 4L80E and fuel injection.

We are keeping this motor home for about another 8 years while we save for the next motor home. Because of the dramatically reduced price that I could do the 700R4 build and swap for (approx. $1000) I see this as a viable option if I can get at least 1MPG increase in fuel economy. With our usage that would pay for the swap within the nest two years and the next 6 years would be nothing but savings. Like you said though.......will the volume of fuel needed to produce the necessary torque at the lower rpm negate my upgrade?

[Mekanic]

there are some things like the alum pump in the 700 trans that can'tbe made as good as what the 400 trans allready has from the factory.
When GM came out the 700R4 trans they didn't put it in heavy trucks for a reason.

[Winnebeater]

Originally Posted by Mekanic

there are some things like the alum pump in the 700 trans that can'tbe made as good as what the 400 trans allready has from the factory.
When GM came out the 700R4 trans they didn't put it in heavy trucks for a reason.

I'm just curious, but did they change anything over the years of production? I ask because I read that in the later years of production they had the 700R4 in Suburbans and Pick-ups. Did they improve something that allowed this?

[fleamarketer]

Originally Posted by Winnebeater

Only problem with this is that the transmission ($3800) and stand alone controller ($1200) plus the additional upgrades (roughly $500) cost more than the NADA guide on my motorhome. If I had the extra $5500 to make this a viable option I would opt to use it on a down payment into my savings account for the future purchase of a newer motor home that would already have a 4L80E and fuel injection.

We are keeping this motor home for about another 8 years while we save for the next motor home. Because of the dramatically reduced price that I could do the 700R4 build and swap for (approx. $1000) I see this as a viable option if I can get at least 1MPG increase in fuel economy. With our usage that would pay for the swap within the nest two years and the next 6 years would be nothing but savings. Like you said though.......will the volume of fuel needed to produce the necessary torque at the lower rpm negate my upgrade?

I think your pricing on the trans is way high.Those have been out in production for quite awhile and the pick and pull yards should have a ready supply on hand.

[fleamarketer]

Originally Posted by Mekanic

there are some things like the alum pump in the 700 trans that can'tbe made as good as what the 400 trans allready has from the factory.
When GM came out the 700R4 trans they didn't put it in heavy trucks for a reason.

Certainly never consider a 700R4 that was behind a 4.3 V6.Don't let anyone tell you it's the same because it will bolt up.The clutch packs in V8 700R4's are much better.
There was a transitional yrs where the trans was called a 700R4/4L60E.I think it was 1994 or 1993.It was a full 4L60E in 1995.A friend of mine had a 1997 Safari which he mod'ed and installed a Ram-Jet 502 with a controller on his 4L60E.Now that 502 certainly puts out tons of torque and he didn't baby it.It handle that with no problem on a van that was well into the 4,000 lb wt.

[Winnebeater]

Originally Posted by fleamarketer

I think your pricing on the trans is way high.Those have been out in production for quite awhile and the pick and pull yards should have a ready supply on hand.

I think it is too. Unfortunately, I am not comfortable rebuilding one and I do not know anyone that is. So, I would have to purchase a used one from a wrecking yard (at least $300), then pay to have it rebuilt ($1700-$2200, transmission, torque converter and fluid) depending on the shop and options. I would still need the controller unless I wanted to get crazy and find a donor vehicle with a TBI 454 and pull the EFI system and the ECM and sensors too. Either way still too much money unwisely spent.

[Curtis in TX]

I went though this battle about 10 years ago with my Fleetwood, and finally gave up on hopping up the Ford Big Block & C6 combo. Just wasn't enough power for mefor in the long mountain climbs.

I even went so far as to get a rebuilt Spicer 5831 aux transmission and flanges to put in the drivetrain. The Spicer is a 3 speed box, a 2.0 under drive, a 1:1 2nd gear and a .73 3rd gear. Other than it being heavy, it looked to solve my problem of having an overdrive. Not to mention it had that tractor drive ratio under drive to get me out of those sticky spots I seem to always find myself in when trying to find a remote spot to park my base camp for some good 4 wheeling rock climbing!

So, after all that, I decided to just re powered my Coach. I wouldn't advise this as the best way to go.

Here's why I feel this way. I spent over $10,000 (for the parts) installing a Hopped up 5.9 Cummins (350 reliable HP) and Allison 542 transmission. Then Re geared the rear end to 3:56's and installed a limited slip while I was in there. (The Limited slip has been a God Send! ) (It has gotten me out of some mud holes I thought I'd never break free of.)

After all that work, which I did by myself, I feel the best way to go is trade in and upgrade the entire Coach. So far I've invested almost $20,000 in the drive train and it's still leaving me short.
Should have just traded it in and gotten a used diesel pusher.


The down side is the A 542 is only a 4 speed, but it has no lock up torque converter, so my mileage only went up from 6 MPG to 9 MPG. I was hoping for 12. Now, I could put the Spicer behind the Allison, but then I'd still have the slipping torque converter heating everything up. Remember I have this propensity for mountains!

Since I do all the driving anyway, I'm looking for a 6 speed MTD Manual cable shift Transmission for the old girl. It will have the take off gears I need when pulling my rock buggy, and the highway gears to cruise at that elusive 12 mpg I seek. And the Manual will handle the HP rating of the Hot Rod Cummins no problem.

Yea, I could just put in an Allison 6 speed auto like the 2000 or 3000 series and call it good. The Allison would set me back another $5 to $8 K. And let's not forget I'd also have to find a $1500 stand alone computer and harness plus the TPS Sensor. (another $150)

I just think a robust no nonsense manual will be less trouble in the long run (About $3500 complete) and I won't have to worry about the heat and slipping torque converters. Still have the Spicer, never even installed it. Didn't want to cut up my new drive shaft to fit it in there. The Spicer is busy holding the shop floor down!

Yea I know, a diesel pusher won't get me 12 MPG either, but at least I would have some slides and a rig capable of climbing mountain passes.
If I had it to do over, I trade up!

Just thought I'd share!

[Eddie Foy]

Originally Posted by fleamarketer

So here is the 64 million dollar question.Does the volume of gas to produce the torque needed negate the mpg savings.Not the quantity of gas,but the volume of gas.If you where to look at the electronic fuel pumps,there is two very important values.Pressure(the quantity of gas used)and the volume of gas rating.Engines operate on the same basis.

You were doing well till you confused pressure with quantity. The two are not the same. Pumps may be rated to deliver a certain press at a certain flow rate but pressure alone means nothing. The number that is important is GPH at rated pressure..