trans upgrade

fern the T-400's they are heavily modified to take that horsepower, I don't run one I run a powerglide and it was way more expensive than the 62 impala that it came from.

Deano56, I've lost most of the summer doing just what you are considering. Had to work on it as time allowed but I'm just about ready to take put it on the ground, in fact just put the front tires on yesterday.

Not an inexpensive do, but if you have to have a trans worth considering. Mine was in perfect shape but I hope to gain the same things you are seeking, lower rpm's and less noise. If lucky I will squeeze a mile or two more out of it as well. Do know that you will modify to some degree most anything you touch. I had to change the rear section of the trans because the donor trans was different, cross member did have to be moved back a couple of inches, yes drive shaft had to cut. I had new carrier bearing and u-joints installed at the time. Have not gotten the shift linkeage to go through all the gears yet but I'm using the the ez-tcu setup to handle the electronis which has the capability for manual up and down shift with the use of momentary buttons. Using the Cable-X box to keep the mechanical speedo.

While at it I installed Thorley headers and magnaflow mufflers, new heat shields, new bell crank, eliminated the air pumps and complete tune-up. Again, I don't have it on the ground yet but I'm looking forward to it and sure hoping for the best.

I did consider the gear vendors and if I knew then what I know now I won't say for sure, but I'd give gear vendors a little more thought. Gear vendors and headers probably would get me about the same but gear vendor unit are not cheap either and used ones are tough to find.
I've been ask if I regret the decision to change over (especially since I had a good running motorhome), and the answer is I hope not. If I accomplish what I set out to accomplish, less noise noise and lower rpm's, then I'm a happy man. If not, shucks I'll still be happy for the experience.

Good luck

Gear vendors expensive???
Well lets see - rebuilt 700R 1000 bucks, Torque converter 300 bucks, Crossmember mod 300 bucks, Linkage mod 100 bucks. If you have the parking brake on the trans big bucks!! Wiring mod for lockup converter 100 bucks. Drive shaft mod 250. And when you are all done you only have 4 speeds and they recommend you don't tow in overdrive whereas with a Gear vendors you get 6 forward speeds plus you can split gears going up hill. It's cost is around 3200 bucks.
Your call

Two things, First, I would not consider a 700R4 in a motorhome. Even though you can build it, it is a light duty trans and just not designed to take the load. Guys that build them for race, build them to last for a limited number of runs, not a constant heavy load. The one big thing everyone forgets about racers - they break stuff. The see breaking things as the normal cost of doing business.

The 4L80E is the same load rating, and uses many of the same parts as the TH400 did, which has been proven to have long term reliability. The only disadvantage of the 4L80E is weight - but it has to be heavy to be tough.

As far as Gear Vendors vs 4 speed, my big concern with Gear Vendors is torque converter stall speed. If you get the engine spinning too slow, the TC slips, and you loose efficiency. Before I installed the 4L85E, I was running 3.53 gears and a step up 1:1.1 chain case. Unless I was traveling 70 mph, the TC would slip, so it was impossible to save fuel by driving slower. You have to look at your gearing and figure out what your typical operating RPM will be. You need it to be above 2500 RPM, and really should be above 2700 RPM at moderate cruising speeds. Otherwise you won't gain anything.

One other idea to consider would be to change your rear end ratio, and then put different gears in 1st and 2nd for your TH400. You can buy different ratios, which will allow you to still get off the line with a taller diff ratio.

Many ways to skin a cat.

FuzzyKnight wrote:
Gear vendors expensive???
Well lets see - rebuilt 700R 1000 bucks, Torque converter 300 bucks, Crossmember mod 300 bucks, Linkage mod 100 bucks. If you have the parking brake on the trans big bucks!! Wiring mod for lockup converter 100 bucks. Drive shaft mod 250. And when you are all done you only have 4 speeds and they recommend you don't tow in overdrive whereas with a Gear vendors you get 6 forward speeds plus you can split gears going up hill. It's cost is around 3200 bucks.
Your call

You are making a pretty big assumption one is paying shop rates for such mods, but yet no cost to install the Gear Vendors. If one goes for a 4L85E, moving the tans mount is zero cost and a few minutes drilling 2 holes. The linkage should not need modifying. If it does, it may be just extending the mounting hole. I think you are a little high on the drive shaft mod, which doesn't Gear Vendors require a drive shaft mod? Not sure you are really comparing apples to apples. I converted from a TH400 to the 4L85E, and including the controller, was less than 3K. Gear Vendors does not offer a lock up TC.

interesting stuff here, will wait to hear how chazh2616 works out. I doubt very much its not going to cost nearly what was stated above out here where I live.

I meant to say, I doubt it will cost as stated above, there are people around here with smaller shops that have better prices than in the suburbs

With your differential ratios, running an O/D tranny will require more throttle opening at cruising speed, which will reduce your MPG. Something to consider.

Jagtech wrote:
With your differential ratios, running an O/D tranny will require more throttle opening at cruising speed, which will reduce your MPG. Something to consider.

what is my differential ratio?

Lift one rear wheel off the ground and count how many times the drive shaft goes around for one turn of the wheel. Then double that number, because you are only turning one wheel instead of both. That will tell you your diff ratio.

The other way to come up with the correct answer is what RPM are you turning at 60 mph?

BTW: The 4L85e will be a little nicer at .75 overdrive, than .7 overdrive of the 700R4.

And just so you know what the designations stand for, the 700R4/4L60E the "60" means it was originally designed for vehicles with a combined weight rating of 6000 LBS, the 4L80E was originally designed to support vehicles with a combined weight rating of 8000 lbs. The 4L85E - the "5" designation stands for 5 planetary gears instead of the standard 3, and is rated for vehicles up to 16,000 lbs. Hmm, which one do you want in your motorhome?