I doubt this is in the correct forum, but didnt see a drivetrain forum & still cant search..GRRR

ANyway. what is/what was the highest HP limit the 4+3 took? I'm sure some one blew one up. Right now the current one in the car has 137xxx miles on it, as does the rear diff ( all highway driving).
I said f*** it decided to put out some damn power with the 356. But not sure if the tranny will hold.
So any thoughts, comments suggestions?

 

Transmissions are rated by maximum input torque and maximum input shaft speed, so maximum HP would be computed by using maximum torque and maximum input speed in the HP formula, but it's academic since car engines typically don't produce maximum torque at maximum speed.

As long as you don't substantially increase torque (signficantly more displacement or boost) and you don't exceed the maximum input shaft speed, you should be okay.

Don't know the ratings of this box, but since it's basically a Super T-10 with an OD unit, you can probably look up the peak torque capacities for the T-10 on the Richmond web site. Match to the installed ratio set. Shorter first gears reduce peak torque capacity since they multiply internal torques.

The OD unit was probably designed to take maximum rated input torque and speed, but my understanding is that the O/D unit is the 4+3's Achilles heel and there are few spare parts for rebuilds.

Duke

 

People will tell you, "the Calloway turbo had 5xxhp, "

but my 70k miles OD went bad as soon as the 406 went in, maybe it was just my luck, but I was not about to pay $1100 for a new OD to take a chance on it going out again, so I opted for a ZF 6.

When I spoke with companies that rebuild the 4+3 OD's they told me not to put another 4+3 OD behind my 406, and they could have told me otherwise.

 

If it's like the older SuperT10's then they will not handle a stout builup, I blew mine a couple days after installing the 406ci and was working on blowing another untiL I ordered a TKO 600 You are looking for trouble at anything over 300RWHP

 

If it has 137k and it's stock, something will definetly go if you're running it hard with all that extra power.

Make the tires the weak link, don't do anything crazy with it, and you might just be OK for a long time.

Don't do 1-2 powershifts, don't hit nitrous while in 3rd gear at 2000 rpm.

I ran a very stout 421 cid motor with my stock 4+3 and drag radials, about the same mileage as yours. It lasted for about 3 months, and I think what killed it was just what I said above: Rolling along in 4th gear at 2500 rpm doing 60, and going full throttle... The tires really wouldn't break loose in 4th (although they would in 3rd if you pulled the same stunt), so all tranny put up with lots more tourque than it could for several seconds at a time.


Oh, and ALWAYS ALWAYS ALWAYS when you are shifting in or out of overdrive, USE THE CLUTCH! Have the clutch pedal fully pressed down for a good second before you hit the OD button. Trust me on this one, you don't want to be running any kind of torque through the car when you engage or disengage the OD. Eventually the OD will wear out, unless you're just farting around tiptoeing on the gas, and even then I would still use the clutch.

Get the stock computer programming CHANGED right away or install a manual OD switch, since the computer does it's own thing with the OD depending on the model year. All kinds of clunks will occur, trust me. You don't want to run any kind of power through the unit when the OD is engaging or disengaging, man I hope I don't sound like someone's dad, I don't mean to lecture, just take my advice for a long life out of the 4+3!

I run the SK beefed up overdrive unit, and still use the clutch, even when playing "top-end games", it's better to lose a car length or two on the 4th-->3rdOD shift than to make the gears go CRRRZZZKKKKCCCHT. Besides, I got ways of making up that lost ground

 

It`s used in Trans Am racing quite often.

 

As stated above it is prolonged torque that destroys these trannys, not so much banging through 1st and 2nd, but for example, you seem to blow them starting at 2500 in third and spinning it up to 6 grand. I think the case twists too much and then things start to go

 

Mine has been behind a stout smallblock 400 for years. Plenty of drag racing and autocrossing, maybe I'm just lucky though.

 

At 400+RWT the SuperT10's don't last long that's all I know I blew the original which was fine behind my 325RWT 355ci the same day I installed my 406ci and the replacement lasted a bit longer but I was trying to save it until I got the new TKO600, maybe the 4+3's are stronger.

 

I used my 4+3 in my 87 only as Overdrive. I locked off the OD except for highway driving. Then if you are going to pass Lock out the OD. I also would press in the clutch to engage the OD. Never had a failure in mine. If you drive it as a 4 speed and OD only for cruise I would expect it to work as well as the base 4 speed. However I reco changing the oil every 25,000 in the OD. It only holds about 2 qt if I remember correctly. Also if the seal fails between the 4 speed and OD unit the gear oil will fail the OD. Don't over tighten the plug or you can't get it out. I would replace it with a steel plug.

So,, summary,, just press the OD button to keep the OD locked out and drive the 4 speed. Change oil frequently.