Quick question about transmissions
-
Suppose you mated a transmission to an engine that spun in the opposite direction of the engine that the transmission was originally designed for… Would this negatively impact the transmission in a significant way?
I can’t think of anything that would cause a problem, since gears are gears regardless of the direction they spin, but I don’t know much about automatic transmissions in particular, whether there are any pumps or anything that won’t work right if they’re spinning the wrong direction.
I figured that you could compensate for the reversed rotation of the transmission by turning the differential/entire rear axle upside down, but I also don’t know if that’s a bad idea. I can’t think of any problems that would cause, beyond installation challenges.
Basically the whole reason I’m wondering about this is that 60s Fords such as mine have massive shock towers that crowd the engine and leave zero room for headers, so now I’m thinking about reverse-flow hot rod engines and whether it would be a good idea to make the exhaust ports the new intakes so the exhaust can exit out the top of the engine, where there’s all sorts of room for headers, with the consequence being that the engine spins backwards. I wouldn’t do this to my own Thunderbird, but if I were ever to hypothetically get another one for racing purposes… I just think it’d be fun to try
-
@awesomeaustinv ...so are you no longer getting rid of it?
The person reading this is a doo-doo head
-
@awesomeaustinv now you’ve got me curious too. Do beveled gears work better one direction than the other?
Civic Si. LR3. Looking for a boat and yeti 3000 iced down w silver bullets
-
@awesomeaustinv being reverse flow doesn’t mean the engine would spin backwards, I think old hot rodders added an idler to make just the cam spin the other way
Honestly not even that, would just need a mirror image cam
-
@awesomeaustinv said in Quick question about transmissions:
I’m thinking about reverse-flow hot rod engines and whether it would be a good idea to make the exhaust ports the new intakes so the exhaust can exit out the top of the engine
If we're talking theoretics; I would just do a cam change to reverse the head flow. The head wouldn't be setup for it though with the intake and exhaust valves the wrong sizes (intake valves needs to be bigger, particularly with NA)
-
@beefchips beveled, no, but helical gears could be an issue if the splines aren't symmetrical
-
@awesomeaustinv If we're just talking theory, I'm pretty sure a torque converter only works in one direction.
-
@awesomeaustinv Im pretty sure it wouldn't work. The fluid flows would be all wrong.
-
You'd have x reverse gears and one forward gear
-
@awesomeaustinv I imagine a manual transmission would be best suited to a reverse direction rotation since a torque converter is most effective in one direction.
I'm unsure if synchros are well suited for a different rotation direction though. Either way, accommodating the reverse spin of a transmission would not be easy since most live axles have breather holes (vent) to allow any pressure buildup to release to ambient, so flipping them over wouldn't be good.<insert signature here>
-
@awesomeaustinv First thing that comes to mind is the pump running backwards on an automatic. And yeah the turbine arrangement inside the torque converter... Also, there could also be roller/sprag clutches that only work one way ("mechanical diode")
-
@awesomeaustinv for manual transmissions I know the VW crowd do it when they swap in Subaru engines. So it can be done
-
@awesomeaustinv said in Quick question about transmissions:
I’m thinking about reverse-flow hot rod engines and whether it would be a good idea to make the exhaust ports the new intakes so the exhaust can exit out the top of the engine, where there’s all sorts of room for headers, with the consequence being that the engine spins backwards.
You wouldn't need to reverse engine rotation to do this. It would just be head & cam work to get intake & exhaust ports on their new sides, and get them actuating properly. The short block won't care as long as everything is timed properly.
But pertinent to the question at hand: I'd be wary of saying gears are gears. Some may not be designed to be loaded the other way, let alone the casing they're inside. They could be, but might not be. Torque converters definitely only work one way, so they would not work if spun the other direction.
-
@awesomeaustinv
Having been in the Corvair world, I can answer this!To reverse rotate a Corvair motor you need a cam and a distributor/oil pump gear. That's it. Why would you need to? If you want to mate it to a VW transaxle! Could you mate it to a VW transaxle without doing a reverse rotation? If it's a VW Thing transaxle. Then you can flip the ring gear to the other side. Then it works fine.
One thing I'm noting in this...they are all MANUAL transaxles. An automatic is an entirely different beast and I do not believe would be happy in a reverse rotation scenario.
So about reverse flow to make it a hot-vee engine....you don't need to reverse rotate at all. Just get a cam an manifolds. The cam would open what is normally the exhaust valve during the intake timing and the intake during the exhaust timing.
Current: '03 Dakota SLT.
-
@EssExTee Nope, I made a post about that a while ago. Felt like I was getting supernatural warnings not to sell it, because it's somehow going to be important soon. So, I'm continuing to pursue its restoration, and I've just saved up the money for the electrical system so now I'm just looking for someone who can help me get that replaced.
-
@Qaaaaa I know not all reverse flow engines spin backwards, but that's the easiest/cheapest way to make it work. Otherwise you need an idler as you mentioned, or what I've seen most people do is just get a camshaft with reversed profiles so it runs the same direction. I'm imagining this being applied to something like a Lemons build, in which case the cheaper the better.
-
@Exage03040 Hmm, I do remember reading that hot rodders who did this usually did some machining on the cylinder heads to make the ports larger. So it's a bit more complicated than just switching parts around.
-
@dogisbadob That's why I mentioned flipping the differential upside down. That puts the crown gear on the other side of the driveshaft so it spins the opposite direction, so the car will still have the right number of forward and reverse gears.
-
@pyroholtz Do you think it'd be possible to plug those holes and drill new ones?
-
@Demon-Xanth Good to know! I guess the common consensus I'm hearing is that it would be far easier and more reliable to just get a cam with reversed profiles. I'll have to look into whether there were any reverse-rotation Ford FE V8 boat motors I could get a cam from...
-
@awesomeaustinv
You don't want a reverse rotation, just a reverse flow. The oil pump will work in the wrong direction otherwise. Look for someone that can grind a cam with the intake and exhaust profiles swapped, but do note that this will likely run about $2-3k.Current: '03 Dakota SLT.
-
@awesomeaustinv probably not cheaper to make it spin backwards. You’d run into weird stuff like fasteners on the sprockets backing out, plus you would then have many reverse gears and only one forward gear.
-
@Demon-Xanth cheaper than that. I think @awesomeaustinv ’s car has an FE engine, which was used in marine applications with reverse rotation. So throw a reverse rotation cam in a forward rotating reverse flow and it’ll work? Maybe?
-
@Qaaaaa
This is the issue:
A reverse rotation cam has the gear teeth angled the opposite way in order to drive the oil pump in the proper direction. Plopping in a reverse rotation cam and running it forward will make the oil pump try to pump oil into the sump.
Current: '03 Dakota SLT.
-
@Demon-Xanth word, I know barely anything about those except that they exist. Profiles wouldn’t be appropriate for a reverse flow anyways so a custom cam would be required for sure
