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| 904 - overdrive options? https://slantsix.org/forum/viewtopic.php?t=55641 |
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| Author: | Reed [ Mon Jun 23, 2014 12:19 am ] |
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I think the closest answer to what you are looking for would be keeping your stock transmission but adding a divorced Laycock overdrive unit behind the transmission. Fabrication work would still have to take place, but you could keep your pushbuttons and stock trans. |
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| Author: | Sam Powell [ Mon Jun 23, 2014 6:03 am ] |
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Tim, Thanks for the link to Maximum Overdrive! That looks like it is worth investigating. Did I understand you to say a custom adapter must be made? They list a Chevy one (of course). I will give them a call today and fine out what they have and how it works. It looks like maybe they have the same electronic control that GV uses. Sam |
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| Author: | Reed [ Mon Jun 23, 2014 9:29 am ] |
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Sam- I am also intrigued by the Maximum Overdirce setup. I was most interested in their stand-alone unit tht doesn't mount to the back of the trans. A second crossmember would have to be fabricated, but it looks like it installs in the middle of the driveshaft path completely independent of the trans. This is the kind of unit I would be interested in. http://www.maximum--overdrive.com/products.html Given that the control kits alone cost $300, I can't imagine that this is really a cheap alternative to Gear Vendors. However, I think this is about th eonly option for a pushbutton trans to get overdrive. I would laso be concerned about ground clearance in an A-body. The sump on that unit looks like it would hang at least four inches below the driveshaft, which would put it almost on the ground in a stock A body. |
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| Author: | emsvitil [ Mon Jun 23, 2014 3:42 pm ] |
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It's probably possible to make your own control unit.......... Simplest would be a pushbutton to activate a latching relay to turn the overdrive on. Then brake activation to unlatch the relay. (or another switch) For the pushbutton you could use a center-off momentary 2 way toggle. Toggle up, overdrive on; Toggle down, overdrive off (plus have the brake switch) |
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| Author: | WagonsRcool [ Tue Jun 24, 2014 11:41 am ] |
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The behavior that you describe is typical for most cars of that era. Both stick shift & automatics had 1:1 top gear. (there were still lots of 2-spd auto's). No one really cared about fuel economy. If you had to spin the engine faster to hit 70-75 then so be it. The big V-8 cars could get away with taller gears because they had gobs of torque & most would spin more rpm's than a 225" slant. Remember, the slant was the budget/entry level engine- no way was it supposed to keep up with all the V-8 traffic. When I got my 63 Valiant, is was stock. 225", auto, 1bbl, 13" tires, 2.94 axle ratio, 1 3/4" head pipe to 1 1/2" tail pipe. It would get up to 70 OK, but if you mashed the gas hard, the engine would make more "noise" as the trans downshifted & the car would slow down. On the other end was my stock 68 Dart auto with a 170". It would spin "to the sky", but was difficult to drive in modern city traffic. I'd pull the shifter to "L", give it lots of throttle...& wait for RPMs to build. The car would really start to pull at 15 & then I'd pop the shifter to "2" at 25-30. Repeat at higher speeds for 3rd. All the while every econo box & family sedan is driving around me & pulling away. Short form is that there's no OD for early slant A-body without lots of money, time, & fabbing skill. |
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| Author: | Reed [ Tue Jun 24, 2014 11:53 am ] |
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The best way to maximize fuel economy is to think of the drivetrain from engine to rear axle as a package. Find out what RPM makes the engine operate most efficiently and then gear the car in the transmission and rear axle to go the speed you want as close to that RPM as possible. Keep in mind you will have to balance the in city stop and go acceleration performance with the highway cruising performance. You may need to just accept that your car cannot comfortably go 75-80. Or, you may need to modify your engine so it makes enough power at lower RPMs to go faster. |
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| Author: | Sam Powell [ Wed Jun 25, 2014 3:25 pm ] |
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I called Maximum Overdrive yesterday and talked to Glen. Short answer, there is no adapter for the Volvo overdrive other than Gear Vendor's and they want $900+ for that. Here is more info. 1. They will rebuild a used GV unit or Volvo for $595 provided none of the gears are broken. GV will NOT sell gears to rebuilders. 2. YOu can buy used Volvo units for about $150 on ebay. 3. The Volvo units will support the HP of a stock slant, but little more. 4. He can rebuild both GV and Volvo units to take more HP, up to about 500hp, but the cost is $100 more. 5. He does sell new units, but I do not remember what they cost. I do remember that by the time you bought the controller and adapter you were up to the cost of a new GV OD kit. If you purchased GVs adapter for $900, and and MO's rebuild of a used Volvo uniti at $150+600, and added their electronic controller for $300, you would have a total of $1950, which would save you almost $900 over a new GV unit. Of course you would need to deal with the u-joint issues and shortening the shaft. It might work. The main advantage of the GV kit is that it is all designed to work together, and I suspect there will be no issues to work out. But, it is expensive. Glen is eager to talk, and would likely be happy to work through solving technical issues. I broached the topic of a group buy for Mopar adapters, and he said there is just not enough market support for it. He would need 100 orders, prepaid before he would see any return on investment. Sam |
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| Author: | Reed [ Wed Jun 25, 2014 6:10 pm ] |
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Bummer. So it sounds like stick shift or A-500 are still the "easiest" ways to get overdrive behind a slant. |
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| Author: | SlantSteve [ Wed Jun 25, 2014 8:26 pm ] |
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MO and Gearvendors obviously know the market well......but I'm really surprised anyone with a GM or Ford vehicle would bother,both vehicle manufacturers make a selection of good transmissions that swap into early cars...would have thought the Mopar guys would have been more of a market for them....oh well.....thanks for researching and posting the info Sam! So the bottom line is for a push button 904 you can either use a divorced MO unit and deal with the issues of aligning two drive shafts and getting angles correct to avoid vibration or make a custom adaptor... Not great news either way. |
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| Author: | Eatkinson [ Thu Jun 26, 2014 7:03 pm ] |
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Thanks for doing that research. Obviously this question has been on the minds of more than just a few of us. I'll have to content myself with driving slower and letting traffic pass me by. The problem seems particularly pronounced here in LA where the speed limit may be 65mph in town, but it might as well be 85mph, as most drivers ignore posted limits and drive however fast they want to. I'm realizing now that had older cars driven just as easily as fast as today's vehicles, people would have. It was only the technological limits of the day that kept people from 'normally' driving so fast. |
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| Author: | SlantSteve [ Fri Jun 27, 2014 1:11 am ] |
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I'm just throwing this idea out there ...it's certainly not and ideal fix,but,would it be possible to swap a planetary from an A500 OD unit into a 904? Sure,the ratios would be very widely spread,but it might be a cheaper way out? Remember that driving at 75 mph in a classic is one thing,you still have to make sure the suspension and braking are capable of stopping it. |
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| Author: | Dan-o [ Fri Jun 27, 2014 6:21 am ] |
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I am constantly battling this as well. I really like the Push Button stuff, and its always a point of pride when you can show someone you got all that old junk to work. However, Gear Venders does NOT make and adapter for the PB904. So at that point it makes me want to ditch the PB stuff and just put another trans in it. Sad part is, the 62 is the wifes DD, so it has to me dead-nuts reliable, so it makes it hard. The more I look at it, the more I think it's time to look into putting a more modern driveline in her car. |
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| Author: | Reed [ Fri Jun 27, 2014 7:24 am ] |
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Quote: I am constantly battling this as well. I really like the Push Button stuff, and its always a point of pride when you can show someone you got all that old junk to work. However, Gear Venders does NOT make and adapter for the PB904. So at that point it makes me want to ditch the PB stuff and just put another trans in it. Sad part is, the 62 is the wifes DD, so it has to me dead-nuts reliable, so it makes it hard. The more I look at it, the more I think it's time to look into putting a more modern driveline in her car.
Why? A rear axle gear change would be easier. If you are looking for a good balance of economy and performance, try using a rear axle gear ratio of 2.9 to 3.2. My brother's 83 Dodge van is powered by a 225 and has a 904 and a rear axle gear ratio of 3.2. It will comfortably cruise at 60-70 MPH loaded and will turn 2500 to 2700 RPM to do it. Not too bad.A slant with a 3 speed automatic should be able to keep up with modern traffic no problem, provided the rear axle gear ratio is chosen thoughtfully. |
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| Author: | Dan-o [ Fri Jun 27, 2014 9:24 am ] |
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The car has 2.76's in it right now with a 275/60/15 rear tire. It cruises at 70mph/2600rpms. Way too high IMO and it brings the exhaust right in the droning sweet spot. We could have a lot more performance and cruisability for our power with 3.73/3.92's and an OD. |
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| Author: | Reed [ Fri Jun 27, 2014 11:30 am ] |
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I would switch to 3.2 or even 3.5 gears and get a quieter exhaust. If you must have an OD, then a stick shift or A-500 and fabrication are the only ways to go. |
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