Good morning, Steve;

When looking at the Gear Vendors web site, I think they said that their unit is a 22% overdrive, and not a 15%. Will that affect your calculations?

Still, if it calculates out to almost anything near by, it would be neat to have an 8 speed transmission.

I am also considering this for the GM 3L80 in the Winnebago Elandan. It calculates out to a beautifully staged six speed with their GV 3D0475.

Enjoy;

Ralph
Latte Land, Washington

You are correct, the Gear Vendors is a 22% and I checked the 480 is 25%. Not sure where I got the other numbers.

I may go that route with a heavy duty rebuilt 475 transmission in front.

Steve,

You may also want to consider the 20% overdrive box, first built by USGear, then Doug Nash but now out of production, although many parts are off the shelf stuff. Simple bolt up to T400, cut driveshaft 6", wire through a 3 pole foot dimmer switch & good to go. Allows 20% OD in all gears.

At 24' w/ the 454, I was a little over-powered. The OD unit sure did quiet things down in Drive, plus gave me a good ratio in Second for long uphill events. I never noticed much fuel savings, but that's because I increased routine cruise speeds due to reduced rpm' & associated noise.

eBay & CL seem to list them frequently. Might be worth a look......

My 502 is rated at 512 lb ft. I have disabled the throttle kickdown. This avoids full-throttle activated kickdown.

If I need a lower gear, I let off the throttle for a few milliseconds while I downshift with the shift lever. This is much easier on the transmission. Hard downshifts really shorten a tranny's life.

Good morning, Steve;

One quick question: Is the "475" also known as a "TH-475" or "the heavy duty Turbo-Hydramatic 400" three speed GM transmission? I think that is also what I have been calling the GM 3L80 three speed automatic transmission.

I believe that the 3L80 is considered by many to be the most durable automatic transmission that General Motors built. And when coupled with the Gear Vendors 3D0475 22% Overdrive, it becomes one really beautifully staged six (6) speed transmission. From First to Second Over, there is a nicely stepped 22% change in ratio as you go up, but when you go from Second Over to Third, there is only a 15% change, which is right where you would want to have a closer ratio between top gear and the gear just below it. That helps when coming up to top speed or anywhere that you want to end up as high on the torque curve as you can when you get to top gear.

Then you have the standard 22% drop in ratio as you go from Third (Top) gear to Third Over, but at this point you are going to overdrive for better fuel economy, less engine noise, and leas load and spinning of the engine while you are running on level ground. And if you have made any modifications to the engine to improve the mid-range torque (for us, right about 3000 RPM), it should pull that light load on overdrive very nicely.

If you are pulling a 4000 pound car, or something similar, then you have the choice to drop back to Third or Top gear for the standard top gear ratio to keep everything spinning happily and not bogged down or overloaded.

I like the idea of an overdrive, if you also do what may need to be done to keep the engine happy and pull the overdrive at the reduced engine speed that you will be running, such as what you have available with your 454HO engine. For me, that is a Banks PowerPack and a modified ignition system. Later there also may be an aftermarket TBI system with a Closed Loop O2 Sensor Feedback Control System.

Enjoy;

Ralph
Latte Land, Washington

I've seen specs where the TH400 was rated at 450 lb-ft.

IMHO, the weak spot in the 4L80E is the torque converter. A failed TC is what caused me to do the upgrade, including the robust Suncoast Converters TC.

Description of many THs is here.

Finally got to drive 86Barth!

Runs very well. Good oil pressure, temps, etc. Took a 15 mile drive with the computer connected, the sensors are all in happy ranges, no error codes. I may not need to get anything done to the computer chip after all.
Too soon to drive it hard but the off idle and low end throttle response is noticeably better. More midrange torque for sure.

No leaks or other problems yet. The idle is a bit low and lopes a bit when idling in drive. Partly the cam I'm sure but I can bump it up a bit by resetting the base air flow rate of the TBI plates.

When I get a few more miles on it I will romp some hills and see what it will do. So far I am very pleased.

Great news. One more off you list.

quote:

Originally posted by Doorman:
Great news. One more off you list.

Makes one wonder what Steve will add to the list to replace it...

quote:

Originally posted by Rusty:
Makes one wonder what Steve will add to the list to replace it...

You had to ask… oh well…

https://www.barthmobile.com/eve...623912487#2623912487

I will have more engine updates when I can.

Hey, Steve;

Were you able to find a hill to romp up with the 454HO over the last month or so? Any other performance data noted in that time? Passing ability, MPG, general "driver satisfaction quotient," et cetera?

Or did the hot water heater project take all your time back in January?

Enjoy;

Ralph
Latte Land, Washington

I finally got to run it… started in Kalkaska, ran to Canton Mi (15 degrees) on Tuesday. Runs stronger than the original but I hadn't floored it yet.

On Thursday morning we left Mi, about 10 degrees and falling. Planned to drive until it we found a warm place. Well, we drove to northern Alabama and it was still 20 degrees and light snow in the air! over 600 miles. Talk about a "Michigan tailwind!

We drove today to rv park near Troy Alabama. We will stay tonight and Sat nite, then off to Florida.

Meanwhile, I had some question about where to set the timing on the new engine. GM calls for 4 degrees, fuel injection guy says 6 and the the Thorley guys say 12! Since the computer does the timing on the fly I can't check maximum advance easily. I started with 4 degrees to be conservative. Starts and runs great, throttle response a bit sluggish, no sign of knocking and more power all over the rpm range.

After a couple tankfuls, I was getting 6.3 to 6.5 mpg same as before. Since I had several hundred miles on it I decided to tweak a bit. I advanced the timing a few degrees. Big improvement! Better throttle response, more power, still no knocking!

I can accelerate up hills I couldn't make before. I will advance timing a few more degrees until I get it to knock, then back off.

The throttle response and acceleration are better than they ever were. The idle is smooth and stable, oil pressure about 35 psi at idle, 65 running. Used 1 qt oil in first 1000 miles.

So far I am very satisfied.

to be continued.

Are you at Deer Run? Stayed there myself on occasion...

Yep. Just got done rinsing the salt off the coach.

Steve VW , i am wondering , is it normal for a NEW 454ho engine to use 1 qt of oil in 1000 miles ?

My 1986 barth stock 454 used about that , but most of that was leaking at the rear 2 piece seal . Bob