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| Realistic options for an overdrive automatic transmission https://www.slantsix.org/forum/viewtopic.php?t=62551 |
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| Author: | Reed [ Sun Jul 15, 2018 6:56 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Josh- actually, about an hour after I responded, it dawned on me that you were talking about replacing the tailshaft and tailshaft housing with the one from the shorter Jeep unit. I felt like a dope! You were fine, I was just not thinking clearly. A FIVE speed auto? That would be great, but I bet it would involve a standalone trans compiuter controller. Tim- I have been looking at Maximum Overdrive, but didn't see any prices listed for the parts you mention. Thanks for providing those. I was ogling that divorced unit but hoping I could cobble something together and make it part of the trans. If they sell a custom tailshaft that is splined for the Laycock unit, that would make it easier to adapt since it would eliminate a few couplings. I could assemble a 904 with a custom tailshaft and tailshaft housing with the OD unit all in one. I would just need to fabricate the tailshaft housing to go from thew 904 case to the OD unit case. But then I would need a custom driveshaft with a slip joint since the Laycock output is just a flange. In the long run it may just be cheaper and easier to go with an adapter plate and an A500 or 200-4r/700r4. Lots to think about and plan. |
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| Author: | Reed [ Thu Jul 19, 2018 12:35 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Well, looks like my path has been made clear. I found a good deal on a factory Chrysler adapter plate and crank spacer with hardware. So I will be going the A500 route. Frankly, this looks like the cleanest, cheapest, and easiest way to get automatic overdrive behind a slant. Plus, it should hook up to all the factory peripheral stuff easier. I will document the installation in my truck once I get around to it. |
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| Author: | Joshie225 [ Thu Jul 19, 2018 5:10 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Yes, that's probably the easiest swap. The A500 with the known reliability improvements and a good cooler should be fine. I do wish the overdrive were not so steep, but that's not such an issue unless towing. |
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| Author: | Reed [ Thu Jul 19, 2018 6:20 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
I will need to research what upgrades are necessary. I understand the A500 uses a larger trans cooler line than the 904, so I will have to abandon the factory in-radiator cooler. However, I already have a HUGE external cooler I can mount in front of the radiator. Lots of little things to work out. Driveshaft, cooler, shift linkage, OD control, etc... All in good time. My next step is to find an A500. |
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| Author: | Reed [ Thu Jul 19, 2018 7:04 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
A-HA!!! http://www.4wdmechanix.com/Survival-Upg ... ssions?r=1 |
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| Author: | afastcuda1970 [ Thu Jul 19, 2018 8:43 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Quote: Driveshaft, cooler, shift linkage, OD control, etc...
Driveshaft: 727 yoke and -3 1/2 inches.Edit: add the thickness of adapter plate.Cooler: bypass radiator and add large external cooler as noted. Shift linkage: use shift and TV arms from a 727. Od & LU control: https://transmissioncenter.net/?s=727+to+518+swap Ect: fabricate trans x-member with common shivvy trans mount. |
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| Author: | Reed [ Thu Jul 19, 2018 9:46 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Thanks! Fortunately, my truck was built with a 727, so I have most of that already covered. I hope to be able to just use the original trans crossmember but drill some new holes in the frame. Time for more research. |
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| Author: | afastcuda1970 [ Fri Jul 20, 2018 6:51 am ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Quote: I hope to be able to just use the original trans crossmember but drill some new holes in the frame.
If your x-member is the same as a 1985, you won't be able to do that. The loop where the tail shaft goes through is too small and the trans mount on the a500 is lower than the 727. You could use a x-member from a '88-'93 truck with an OD trans. |
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| Author: | Reed [ Fri Jul 20, 2018 8:29 am ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Hmmm. I will try to use a factory 88-93 mount before I test my poor fabrication skills. |
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| Author: | Tim Keith [ Sat Jul 21, 2018 3:23 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Reed, I think keeping the 3.9 gear is a good choice. The A-500 variants can built with most of the heavy duty parts that the A904 can use but Tom Hand's transmission book doesn't mention the overdrives. The overdrive unit is the same as the A-518. I think the A-500 will work well in the truck, especially with a cooler. I might do the same thing as I believe there is adequate space for the A-500 in the 1/2 ton trucks. |
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| Author: | Reed [ Sat Jul 21, 2018 3:34 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Can an A500 use 904 parts? I have a freshly rebuilt 904 with heavy duty parts under my workbench. I wonder if I can just swap the guts over? I have found a few A500s at junkyards for $400, but I am hoping to find one at a picknpull for cheaper. I want to get the cooler lines, o/d switch and wiring, and trans mount from the same vehicle if possible. |
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| Author: | Reed [ Sat Jul 21, 2018 4:09 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Argh! I just found this on Moparts: "Nobody has mentioned yet that 904's/A500's use a smaller diameter ring gear on the converter than an A727/518 does, which locates the starter about 1/2" closer to the crank, and the adapter may need trimming for starter clearance." Can anyone confirm this is true? Will I need to worry about trimming or grinding the adapter? 
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| Author: | DusterIdiot [ Sat Jul 21, 2018 10:06 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Quote: Will I need to worry about trimming or grinding the adapter?
I think Lou posted in one of his firsts posts of doing this conversion decade plus back, that it took some grinding on the stock adapter and the AREngineering unit since the A-904 is a smaller scale copy of the A-727 in many respects and the bell has a slightly different cross-section than the 727 version... |
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| Author: | Reed [ Sun Jul 22, 2018 12:05 am ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Thanks Rob. I will dig around and find Lou's posts. 
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| Author: | Tim Keith [ Sun Jul 22, 2018 11:16 pm ] |
| Post subject: | Re: Realistic options for an overdrive automatic transmission |
Quote: Can an A500 use 904 parts? I have a freshly rebuilt 904 with heavy duty parts under my workbench. I wonder if I can just swap the guts over? I have found a few A500s at junkyards for $400, but I am hoping to find one at a picknpull for cheaper. I want to get the cooler lines, o/d switch and wiring, and trans mount from the same vehicle if possible.
I think many A904 parts fit the A500. I believe the V8 A-500 has some stronger parts from the six cylinder version. You can cross reference the heavy duty 904 parts and see if they fit the A500. The A-413 front drive transmission can also use many A-A-904 parts.
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