Slant Six Forum :: 904 - overdrive options?

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.

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.

I THINK you could fit the newer wide-ratio 904 gears in the trans, and the 2.45's in the rear. It's still not OD, and it's not a weekend job. Should improve highway driving though.

That will only get a lower 1st and 2nd will not change the 3rd gear will still have 1 to 1.

What happen to all the 700R4 guys?

Have been in further communication with Glenn of Maximum overdrive. It seems he can take a Volvo overdrive and make all the mods to make it work with the Mopar 904. He sells rebuilt units for $600, and charges $255 for changing out shafts to mate with 904 and Mopar drive shaft. If you want Hi Po mods that is more.

A new GV adapter is $950, ant the electronic control is $300. This brings the entire package up to 2105 plus shipping and drive shaft costs. This is $650 less than the GV kit. There is still the open question of the speedo drive. I THINK Glenn's $255 includes that, but am waiting for clarification on that.

When all is said and done, I feel the extra $600 from GV might be worth it for the warrantee, known 1200 hp rating, and r&d already done and known to work together. If I had been able to purchase an adapter I was prepared to go the 200r4 route. If you have one, it seems a good way to go.

Sam

Quote:

Still leaves the PB904 guys out in the wind.

Author:	SlantSteve [ Fri Jun 27, 2014 2:17 pm ]
Post subject:
The only other option is to fabricate an adaptor to fit the OD unit directly onto the trans....lots of work,but a neat way of doing it. Personally, I don't like the way gearvendors use a long extension housing,I understand WHY they do it that way, it's a lot more work to shorten the output shaft etc etc,but it would be a nicer way of going about it.

Author:	Dan-o [ Fri Jun 27, 2014 3:16 pm ]
Post subject:
Quote: 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. Shortening the gears would just make the RPM's and drone higher, makes no sense. The car has Flowmaster Delta 50's and full exhaust, unless I decide to throw a Dynomax Super Turbo on, it's about as quiet as it's gonna get. The wife doesn't want a 5-speed in her DD, I think it's time we all just admit that it's time to move on from the /6,s LA's and B/RB's and go with 3g HEMI's and 5-6 speeds (auto or manual). I'm hoping they can figure out some stand alone junk for the PentaStar, because at 305hp and a 8 speed auto would be really fun in an old Mopar for cruising.

Author:	Joshie225 [ Fri Jun 27, 2014 4:40 pm ]
Post subject:
Quote: 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. 2600 RPM at 70 MPH is too high? The math (http://www.corral.net/tech/gearcalc.html) says 2320 RPM with no slippage so you should see maybe 2500 RPM tops with a stock torque converter. 2600 RPM is still quite reasonable for that high a cruise speed. My '67 Valiant spun 2900 RPM at 70 MPH with 3.21 gears and did so without complaint. My 30-year-newer, 5-speed automatic, 3.2l I-6 car turns 2500 RPM at 75. 100-200 RPM isn't a big difference, but I'd bet my exhaust and interior are significantly quieter.

Author:	lowbrowsickser [ Sun Jul 06, 2014 7:16 am ]
Post subject:
I THINK you could fit the newer wide-ratio 904 gears in the trans, and the 2.45's in the rear. It's still not OD, and it's not a weekend job. Should improve highway driving though.

Author:	Fopar [ Sun Jul 06, 2014 8:40 am ]
Post subject:
Quote: I THINK you could fit the newer wide-ratio 904 gears in the trans, and the 2.45's in the rear. It's still not OD, and it's not a weekend job. Should improve highway driving though. That will only get a lower 1st and 2nd will not change the 3rd gear will still have 1 to 1. Richard

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904 - overdrive options? https://slantsix.org/forum/viewtopic.php?t=55641	Page 3 of 4

Author:	Kidd [ Sun Jul 06, 2014 8:55 am ]
Post subject:
To the origional poster: Borrow or buy a set of small bolt pattern 14 inch rims, and run the taller tire for a week. You will see a difference.I read that you like the hub caps.....but if you are wanting an RPM drop, and the 14 inch wheels work, you could spend the extra money to have some adapter rings made to put the hub caps on. I think I have some extra 14 inch small bolt pattern stockers.....and a couple pairs of aftermarket 14 inch aluminum slamm bolt pattern rims too.

Author:	DusterIdiot [ Sun Jul 06, 2014 9:39 am ]
Post subject:	Engineering...
Quote: That will only get a lower 1st and 2nd will not change the 3rd gear will still have 1 to 1. Exactly. This route prescribed was to try and make the 904 kinder with the drop to the 2.45 gearing (compared to the original poster's current gear ratio) to lower the rpm in 3rd with that gear ratio ...the problem there is terrain, the 2.45 in 3rd is fine for flat land driving on a stocker slant, but hills will cause it to drop to 2nd most of the time...having a torque build slant helps a bit, either way if the build drops out of it's optimum powerband the end user's mileage will suffer. 2 cents

Author:	sandy in BC [ Sun Jul 06, 2014 11:47 am ]
Post subject:
What happen to all the 700R4 guys? I thought that was the auto OD trend......

Author:	Rick Covalt [ Sun Jul 06, 2014 12:58 pm ]
Post subject:
Quote: What happen to all the 700R4 guys? They are still out there, but a lot of adapters are just setting on the shelves waiting for time and money. If you think about it you probably have $2500 plus to do a new transmission, adapter, and install. Maybe more depending on the options you want. Rick

Author:	Sam Powell [ Mon Jul 07, 2014 5:43 am ]
Post subject:
Have been in further communication with Glenn of Maximum overdrive. It seems he can take a Volvo overdrive and make all the mods to make it work with the Mopar 904. He sells rebuilt units for $600, and charges $255 for changing out shafts to mate with 904 and Mopar drive shaft. If you want Hi Po mods that is more. A new GV adapter is $950, ant the electronic control is $300. This brings the entire package up to 2105 plus shipping and drive shaft costs. This is $650 less than the GV kit. There is still the open question of the speedo drive. I THINK Glenn's $255 includes that, but am waiting for clarification on that. When all is said and done, I feel the extra $600 from GV might be worth it for the warrantee, known 1200 hp rating, and r&d already done and known to work together. If I had been able to purchase an adapter I was prepared to go the 200r4 route. If you have one, it seems a good way to go. Sam

Author:	Dan-o [ Mon Jul 07, 2014 12:33 pm ]
Post subject:
Quote: Have been in further communication with Glenn of Maximum overdrive. It seems he can take a Volvo overdrive and make all the mods to make it work with the Mopar 904. He sells rebuilt units for $600, and charges $255 for changing out shafts to mate with 904 and Mopar drive shaft. If you want Hi Po mods that is more. A new GV adapter is $950, ant the electronic control is $300. This brings the entire package up to 2105 plus shipping and drive shaft costs. This is $650 less than the GV kit. There is still the open question of the speedo drive. I THINK Glenn's $255 includes that, but am waiting for clarification on that. When all is said and done, I feel the extra $600 from GV might be worth it for the warrantee, known 1200 hp rating, and r&d already done and known to work together. If I had been able to purchase an adapter I was prepared to go the 200r4 route. If you have one, it seems a good way to go. Sam Still leaves the PB904 guys out in the wind.

Author:	64 Convert [ Mon Jul 07, 2014 1:01 pm ]
Post subject:
When my stock geared, stock slants were new, it was no problem to cruise all day at 70-75. My '64 Valiant with 3.23 gears is very comfortable at 70, but I've rebuilt the suspension and steering, as well as put $100 of good sound deadening insulation in the floor and new weatherstripping in the doors and windows. In my opinion, it's more the age related noises that make higher speed driving worrisome and annoying, not the engine RPMs. I did a similar thing in my '73 Dodge truck. Even new it was noisy, but with sound deadening insulation, new, thick carpet, padded headliner, and fabric insulation to replace the hard plastic, it's nearly as quiet as a new truck at 70, and it has 3.55 gears.

Author:	Sam Powell [ Mon Jul 07, 2014 1:30 pm ]
Post subject:
Quote: Quote: Have been in further communication with Glenn of Maximum overdrive. It seems he can take a Volvo overdrive and make all the mods to make it work with the Mopar 904. He sells rebuilt units for $600, and charges $255 for changing out shafts to mate with 904 and Mopar drive shaft. If you want Hi Po mods that is more. A new GV adapter is $950, ant the electronic control is $300. This brings the entire package up to 2105 plus shipping and drive shaft costs. This is $650 less than the GV kit. There is still the open question of the speedo drive. I THINK Glenn's $255 includes that, but am waiting for clarification on that. When all is said and done, I feel the extra $600 from GV might be worth it for the warrantee, known 1200 hp rating, and r&d already done and known to work together. If I had been able to purchase an adapter I was prepared to go the 200r4 route. If you have one, it seems a good way to go. Sam Still leaves the PB904 guys out in the wind. What does PB904 mean?

Author:	Reed [ Mon Jul 07, 2014 2:11 pm ]
Post subject:
Push button 904. As cool as pushbutton shifters are, the pushbutton guys are pretty much left out in the cold. The trans was only used for six years behind the slant in passenger cars (60-65) and there are further subcategories (read one or two year only models) within those years. I believe if one wanted to keep the pushbutton transmission yet still have overdrive then the only option is maximum overdrive divorced unit. I don't know if GearVendors would offer a slant pushbutton 904 system.

Author:	Tim Keith [ Mon Jul 07, 2014 8:31 pm ]
Post subject:
I the past week I've found two Borg Warner R-10 overdrives. These are attached to a three speed manual transmission. One of these came from '53 Dodge Coronet with a 241 hemi and the other from a '53 Belvedere with 218 flat head six. I think one of these could work with a slant six. The Laycock J-type overdrive is considered to be superior as it is still in production via Gear Venders. The Dodge R-10 is unusual in that it used the same extended bell housing as the Gyro-matic (Fluid-Drive) semi-automatic, thus the input shaft is very long, but the R-10 unit is the same as for the 218. I don't think it would be extremely difficult to adapt the P-type Laycock from a Volvo 240 to be remote/divorced. I might get a P-type from the PNP and disassemble it just for fun. You can purchase aftermarket input shafts that fit into the front of the Laycock. You need to build a bearing retainer and a welded adapter from a large diameter pipe. Hobby machinists can do the work. The divorced/remote Laycock must be absolutely aligned with the output shaft of the transmissions. A machinist named Dennis Gronan built these remote Laycocks for the '46 to '68 Dodge Power Wagon, but as of two years ago he no longer builds them. You could call Dennis and ask him how he did it. I think the tail housing could be removed from a 833 and replaced with a custom adapter for the Laycock. If you are skilled with a lathe I think it can be done rather inexpensively. If you are not skilled with a lathe, this might be a good project to learn. And maybe just use the Volvo 240 transmission.

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