johnpas Posted October 12, 2008 Report Share Posted October 12, 2008 I have a 75 cadillac coupe de ville 500 ci engine. I would like to add a new 4 speed . Does anyone know what trans I can bolt up to it? It has a TH400 3 speed now . The TH400 in there now is toast so I would like to upgrade some. John P. san diego CA Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted October 12, 2008 Report Share Posted October 12, 2008 This company offers a variety of transmission adapters, although I don't see your specific need mentioned. MTS offers a variety of products for your vehicle. They also mention in one of the threads in their forum that the offer transmission adapters for the 500s These snippets seem especially relevant: The TH200R4 (that ID may not be exactly correct) 4 speed O.D. tranny's that were behind the turbocharged Buick V-6 engines will usually bolt up to the 472/500/425 Cadillac engines. One thing that comes to mind is the old 'Switch Pitch' TH400. Although it is not an O.D. tranny. It will allow you to run some Freeway Gears in the diff for efficient freeway flying & still be able to come off the line more aggressively. Unfortunately, that's about all I can tell you about them. There is a lot of info to be found on the net if you search with some variation of "Turbo-Hydramatic 400 Switch Pitch transmission." Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
KHE Posted October 12, 2008 Report Share Posted October 12, 2008 I think the biggest problem you're going to have if you install something other than a THM-400 is getting the lighter duty trans. to withstand the torque of the 500 engine. Installing an overdrive trans. would probably require re-gearing the differential in order to match whatever OD trans you install. It's not that it can't be done but rather, how much money do you want to spend? The easiest thing to do would be to rebuild the existing Turbo-400. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
johnpas Posted October 14, 2008 Author Report Share Posted October 14, 2008 I think the biggest problem you're going to have if you install something other than a THM-400 is getting the lighter duty trans. to withstand the torque of the 500 engine. Installing an overdrive trans. would probably require re-gearing the differential in order to match whatever OD trans you install. It's not that it can't be done but rather, how much money do you want to spend? The easiest thing to do would be to rebuild the existing Turbo-400. Thank you all for your comments. Link to comment Share on other sites More sharing options...
Ed Hall Posted October 14, 2008 Report Share Posted October 14, 2008 Your best bet would be a 4L80E hooked up to an electronic controller. Link to comment Share on other sites More sharing options...
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