Turbochargers/Superchargers and Automatic Transmissions?

Whappeh

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This is a very dumb (more then likely) two part question. I've always pondered this as I see people who like to modify cars (and who are generally middle and upper class teenagers who are spending dad's money) but what affect would the added horsepower gain of a Turbo/Supercharger have on a car with an automatic transmission? Would the transmission be able to handle the added power? Maybe I'm overestimating the power added by engine modification or are totally ignorant to how autos work, but its a question I've always wanted an answer to.
 

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Automatic transmissions can handle the power when properly modified no problem. Nearly all of the fastest drag cars run automatics.
 

Whappeh

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Automatic transmissions can handle the power when properly modified no problem. Nearly all of the fastest drag cars run automatics.
So then I guess I'm totally ignorant to how they work, lol. :lol:

maybe I should read into that...

Cheers for the answer, though.
 

thedguy

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When it comes to turbos, automatics are superior. The faster supra's tend to run TH-350 or TH-400's out of GM cars and trucks. The thing with automatics is you can keep a load on the engine, which allows the turbos to build boost. To do that on a manual would trash your clutch, but on the automatic you're just heating oil. The wider gearing (those trannies only have 3 speeds) also puts more load on the engine.

The other thing is, a built automatic is extremely fast shifting, if you ever get a chance to ride in a car with one, you'll then ponder why all the manufacturers are putting so much effort into making these double clutch jobs work.

Lastly, back in the 60's guys racers didn't have the advantage of custom tailored torque converters and the old manual transmissions were weak under the torque of highly modified big block v8's. What they started doing was converting them to use a clutch, and do the tricks needed to make the trans shift faster. On a rare occasion you'll see this mod done on oval/circle track cars running old 2 speed powerglides.
 

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It really depends on how much power you end up getting out of it and what automatic it is. My Series III's Borg Warner 66 is notoriously weak even at stock power levels, so I'm having to swap it out for another transmission (a GM 4L60E) before I can put a supercharger on my car.

On the other hand, things like the XJ12 that already have a GM 4L80E wouldn't need a new transmission or even uprated parts even if the blower doubled their horsepower.
 

MattD1zzl3

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My friends 1996 Chevrolet Caprice 9C1 Impala clone is running 400HP through a 4L60E, its a nice transmission.
 

LeVeL

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I know a kid that has a 9-second automatic camaro.
You can load up power against the torque converter and launch like theres no tomorrow
 

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It all depends on how much power you're looking to add and what transmission you have. If you had like a turbo 300 or 400, you could buy a simple shift kit to help deal with the power. Most automatics are designed to slip when they shift, which makes for a nice smooth ride but increases wear on the tranny, and the shift kit makes them a bit firmer. There are companies that will build up a transmission for you depending on what your needs are.

Sometimes a stock transmission can handle big increases in power without any tweaking at all. The transmission in my car is a 4T65E-HD, it's a slightly beefed up version of the 4T65E that gets mated with standard 3800's and other engines around the same power. But I've heard of people getting more power out of their NA 3800 and having no problems with the tranny. The HD version goes with higher power stuff like the SC 3800 and LS4, and again I've heard stories of upping things a bit and still having zero problems with the stock tranny.
 

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[youtube]http://www.youtube.com/watch?v=tstqE7cdWkc[/youtube]

Both trucks are on their stock automatic trans (probably stalled tho) Auto's will dominate a manual trans at the dragstrip, but nowhere else.
 

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As owner of both an automatic and a manual (no bias) i can vouch for that, all the quick cars are autos. A botched gearchange with 1,500 horsepower would be a very expensive disaster.

Ask around, take it to a transmission shop and have it built up a bit and a stall put in, and you'll be fine with any power increase.
 

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You can generally strengthen an automatic transmission to handle big torque. No different to a manual, where the stock clutch and gears will only handle so much.

On a car with suitably big power, an auto car is consistently quicker than a manual one. There's no "failing" the launch by bogging it down, and the gear changes are quicker and always 100% successful. If you're making enough power, the lack of direct mechanical connection between the engine and driveshafts is not relevant.

Its only in a really underpowered car, where you'd want to launch with more RPM than a stock auto permits, and the parasitic loss from a viscous coupling is actually noticable, that manuals are quicker.
 

awdrifter

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I have a question about auto trans too. For manual cars usually the clutch is upgraded to handle more power (up to the point of gear failure of course), so what needs to be upgraded that's equivalent to a clutch upgrade? An upgraded torque converter? Thanks.
 

scathing

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I have a question about auto trans too. For manual cars usually the clutch is upgraded to handle more power (up to the point of gear failure of course), so what needs to be upgraded that's equivalent to a clutch upgrade? An upgraded torque converter? Thanks.
An auto has cogs, but in a planetary gearset configuration, that could do with hardening or strengthening.

The other bits and pieces, of which there seems to be a list of words here, that can be uprated or replaced.

A common "Stage 1" upgrade for auto transmissions that will be taking a lot of loads is a fluid cooler, I've noticed. It seems to be very common on cars that are subject to towing duties.
 

scathing

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Doesn't change the fact that an auto is a lazy and boring way to drive.
Sometimes that's all you want.

I'd be quite happy if my daily was an auto. I don't care if its a viscous coupled planetary gearset (traditional autos) or a manual-type gearset electronically controlled clutch (like the DSG, SMG, etc), although the former is preferable in an auto since its smoother and less likely to smell.

If I were building a serious drag car for competition, as per the above I'd take an auto as well. In a race car I'd prefer something without a clutch pedal and computer-controlled gear actuation (but with manual selection).

In actual fact, I'd only want a gearbox with a clutch pedal and the mechanical selection of gears in a "driving experience" car. Something fun, but not necessarily comfortable or fast.
 

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An auto has cogs, but in a planetary gearset configuration, that could do with hardening or strengthening.

The other bits and pieces, of which there seems to be a list of words here, that can be uprated or replaced.

A common "Stage 1" upgrade for auto transmissions that will be taking a lot of loads is a fluid cooler, I've noticed. It seems to be very common on cars that are subject to towing duties.
Most people usually go for a reprogrammed valve body and a stall converter first. A friend of mine was building a pro 10.5 Mustang (2,100hp, 7.4@198 1/4 mile) and he had a built 2 speed powerglide.
 

thedguy

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I have a question about auto trans too. For manual cars usually the clutch is upgraded to handle more power (up to the point of gear failure of course), so what needs to be upgraded that's equivalent to a clutch upgrade? An upgraded torque converter? Thanks.
Along with what the other guys mentioned, really high hp stuff will look into changing the clutch bands in the transmission to something a little beefier (I believe the current trend is to use Kevlar bands/clutches).


Doesn't change the fact that an auto is a lazy and boring way to drive.
Drive an automatic with a full manual valve body and the only difference is a lack of clutch pedal. All shifts are manually controlled. You can even rev-match your downshifts. Though since I haven't driven one myself, I couldn't tell you why or how.
 

Eunos_Cosmo

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Along with what the other guys mentioned, really high hp stuff will look into changing the clutch bands in the transmission to something a little beefier (I believe the current trend is to use Kevlar bands/clutches).




Drive an automatic with a full manual valve body and the only difference is a lack of clutch pedal. All shifts are manually controlled. You can even rev-match your downshifts. Though since I haven't driven one myself, I couldn't tell you why or how.
I'll take a full sequential. More simple and more reliable. Although I dont understand how you rev-match on a sequential either. Somebody care to explain if they know?
 
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