Manual valve body automatic transmission - Fuel Economy, Hypermiling, EcoModding News and Forum

Christ · 03-02-2009, 12:54 PM

I'm not sure if anyone has ever discussed this here, but I wondered if anyone had experience with MVB's in street cars...

Personally, I can see both a performance and a MPG gain from it, b/c you can shift whenever you feel like it... (short shifting). Couple that with a low-stall convertor, and suddenly, you're slowly eeking away some of those efficiency losses that auto's suffer.

So if it turns out that this could be a beneficial mod, I'll get right on buying a core trans to work with, since there are several other things to do with the transmission that I'll be working with (Chrysler 31TE - 3-Speed, Lockup, no TCM) and I'll outline them all here with pictures and such so that anyone looking to do the same thing will have a simple resource to look back on for help.

jamesqf · 03-02-2009, 01:05 PM

Seems pointless to me (if I understand it). People (other than a small number of the physically disabled) buy automatic transmissions because they're either too lazy to shift, or too uncoordinated to learn how. So why would they want an automatic that they can shift themselves?

frugal builder · 03-02-2009, 03:21 PM

A manual valve body will eliminate a portion of Automatic trans power waste. It will shift like nothing else, though. There is no RPM reduction during the gear change so the torque converter will be the only place to absorb the shock. The joints in the driveline will need to be of excellent quality. Wet weather drivability will be something that will need to be delt with. It will be so much fun, you may never see a mileage improvement. Build it into a clutchflite and it will be very efficient. What a blast.
The trans can always be reverted to the auto valve body. Use a Transgo shift kit with the low "improved" install if you return it and you'll be happy. They will short shift under light throttle input unless the load is high such as low speed and a steep grade.
Oh, I have lived with them both on the street. 1700 lb car with an 8000 RPM 383 and a 727 with a 4.56 gear set and 31 inc tall slicks had the Cheetah manual valve body. Loved it!!! Never once did fuel use enter my mind. I've had a few shift kit equipped TFs. they all returned better mileage and cooler trans temps. Slippery road conditions need to be addressed with driving adjustments.

Christ · 03-02-2009, 04:19 PM

Frugal Builder - What if I just do the MVB modifications by modifying the spacer plate between the upper and lower valve sections? TurboDIY has an informative walkthrough on modifying the A413 series of transmissions (FWD 31TH), including adding more clutches, band modification, and full manual capability using the OEM valve body... I guess I'd love to know if I can keep fluid pressure modulation based on throttle by doing this?

Like I said, I don't want elephant-kicking-you-in-the-ass-end shifts, especially when I have my Son in the van with me. I'm really looking to have more control over when my transmission is shifting, but keeping it civil.

Christ · 03-02-2009, 04:29 PM

Will I also be able to retain engine braking with that setup? What about my lockup torque convertor, will it still lockup?

I haven't been able to find too many people using it, who also drive on the street often. And as we all know, it's VERY difficult to find someone who does this type of modification with FE in mind.

MetroMPG · 03-02-2009, 05:05 PM

Quote:

Originally Posted by jamesqf

Seems pointless to me (if I understand it). People buy automatic transmissions because they're either too lazy to shift, or too uncoordinated to learn how. So why would they want an automatic that they can shift themselves?

Remember, we're not talking about people here (as in the general public). We're talking about fuel economy, um, enthusiasts.

Would the rest of the automatic driving sheeple want one? Of course not. But who cares? It will be an interesting project for the assembled peanut gallery, and will probably save fuel in the hands of a motivated driver (vs. the stock setup).

If I was stuck with an automatic, for whatever reason, I'd definitely want to be able to control shift points, particularly torque converter lock-up.

malibuguy · 03-02-2009, 05:07 PM

the only time i ever ran a full manual valve body was on Malibu1 with a 3400 stall converter...light throttle shifts weren't all that abrupt cuz of the converter, but any more then about 1/2 throttle, it'll bark the tires

plus with a converter like that gas mileage was out of the question...i went from upper teens low 20s, to 12-15mpg with the car just being parked & not driving it :P

Andyman · 03-02-2009, 07:29 PM

I wasn't sure how to vote on that one. Either the first choice or the last seem appropriate. I think that the most effective modification you can do to an automatic transmission is to make the torque converter lock up at a reasonably low speed. such as 1500 RPM after locking. Another helpful thing is to get lock up working in more gears than just the highest one.

On GM cars the locking can be controlled by an electrical switch installed in the car but my Honda locks its torque converter by hydraulic controls. I would have to take it apart and modify some springs to change its settings. Maybe I could add some kind of manual control of the torque converter by using solenoid operated valves. It locks up at about 48 MPH and slows the engine down from about 2400 RPM to 2000 RPM. A lot of my driving is on local streets with a limit of 30 MPH. It would be nice if I could be using 3rd gear with lockup at that speed. Even 4th gear with lockup might be usable at light load. The engine would be turning 1250 RPM in 4th or about 1800 RPM in 3rd. Normally it shifts into 4th at about 31 MPH but I can shift it to 4th at a slightly slower speed by shifting to neutral for a second and then back to drive.

bwilson4web · 03-02-2009, 07:49 PM

I'm with Andy. You really need to understand the transmission and then run some tests.

Bob Wilson

Formula413 · 03-02-2009, 08:13 PM

Quote:

Originally Posted by jamesqf

Seems pointless to me (if I understand it). People (other than a small number of the physically disabled) buy automatic transmissions because they're either too lazy to shift, or too uncoordinated to learn how. So why would they want an automatic that they can shift themselves?

Quote:

Originally Posted by MetroMPG

Remember, we're not talking about people here (as in the general public). We're talking about fuel economy, um, enthusiasts.

Guess it was just too good of an opportunity to look down his nose at everyone to pass up.

I second (or third?) Andy's comments. I would love to have lockup available in all gears, or at least third. I need at least 37 mph for lockup in fourth, and I often can't go that fast. Plus I would think lockup would yield better engine braking.