# super-duper FWD auto trans? **URL:** \ **Category:** Factual Questions\ **Created:** [September 15, 2014, 2:16am UTC](https://boards.straightdope.com/t/super-duper-fwd-auto-trans/698524 "2014-09-15T02:16:13Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [September 15, 2014, 2:16am UTC](https://boards.straightdope.com/t/super-duper-fwd-auto-trans/698524/1 "2014-09-15T02:16:13Z")
Suppose I wish to bring back to life my grampa’s Olds Toronado, [![](https://upload.wikimedia.org/wikipedia/commons/b/b9/66Toronado.jpg) ](https://upload.wikimedia.org/wikipedia/commons/b/b9/66Toronado.jpg) Eldorado, [http://www.bestautophoto.com/images/tuning-cadillac-eldorado-8.2-06.jpg](http://www.bestautophoto.com/images/tuning-cadillac-eldorado-8.2-06.jpg) or even the GMC Motorhome, [![](http://assets.hemmings.com/story_image/280821-1000-0.jpg?rev=2) ](http://assets.hemmings.com/story_image/280821-1000-0.jpg?rev=2) …all of which had a 3 speed heavy duty auto trans and a 7+ liter pushrod v8…which more than likely required premium gas. (ultra-expensive today) I want to update the relatively inefficient gas-guzzling drivetrain with a modern 6.6 Duramax Diesel. I also want the efficiency of the Allison 5 speed tranny with lock-up torque converter, but alas…the allison is only longitudinally mounted. Is it at all possible to mix-n-match THM-425 parts with the Allison trans? ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [September 15, 2014, 2:42am UTC](https://boards.straightdope.com/t/super-duper-fwd-auto-trans/698524/2 "2014-09-15T02:42:18Z")
Um, the engines on those old FWD cars _were_ longitudally mounted! Here’s what the engine bay of a Toronado looks like: [http://bringatrailer.com/wp-content/uploads/2009/11/1966\_Oldsmobile\_Toronado\_Deluxe\_For\_Sale\_Engine\_1.jpg](http://bringatrailer.com/wp-content/uploads/2009/11/1966_Oldsmobile_Toronado_Deluxe_For_Sale_Engine_1.jpg) The El Dorados and weird RV’s are similar. Since they shared platforms with RWD cars, swapping in a regular old RWD drivetrain is relatively easy as far as these things go. I’m not sure if there’s any modern longitudal-mount FWD transaxle that would work. VW has used a similar arrangement on some Audis with big turbo V6’s that would put the old GMs to shame in terms of horsepower. I can’t imagine the dimensions are remotely the same, though. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [September 15, 2014, 3:00am UTC](https://boards.straightdope.com/t/super-duper-fwd-auto-trans/698524/3 "2014-09-15T03:00:43Z")
> [@GreasyJack](#): > > Um, the engines on those old FWD cars _were_ longitudally mounted! . I didn’t make myself clear. I meant to say, instead of the engine in front and the transmission behind the motor (in a RWD setup) the THM-425 sends engine power 180 deg about-face and the bulk of the trans is underslung under the driver side bank of cylinders. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [September 16, 2014, 12:21am UTC](https://boards.straightdope.com/t/super-duper-fwd-auto-trans/698524/4 "2014-09-16T00:21:23Z")
Looking at this allison 5 speed [![](https://stroyteh.nethouse.ua/static/img/0000/0001/2172/12172302.rc59qfob92.jpg) ](https://stroyteh.nethouse.ua/static/img/0000/0001/2172/12172302.rc59qfob92.jpg) it certainly looks like the bellhousing can unbolt from the rest of the case. Perhaps one can fabricate an Adaptor Plate or Flexplate… [![](http://cliff.hostkansas.com/pffimages3/image030.jpg) ](http://cliff.hostkansas.com/pffimages3/image030.jpg) [![](http://cliff.hostkansas.com/pffimages3/image020.jpg) ](http://cliff.hostkansas.com/pffimages3/image020.jpg) [![](http://cliff.hostkansas.com/pffimages3/image022.jpg) ](http://cliff.hostkansas.com/pffimages3/image022.jpg) [![](http://cliff.hostkansas.com/pffimages3/image008.jpg) ](http://cliff.hostkansas.com/pffimages3/image008.jpg) (this fabrication can take 700 hp)