Tremec 3650 how much can it handle - Page 2

StriderTacticaL · 01-07-2009, 04:16 PM

The thing that blows trannys the most is shock. Like high HP 5K clutch dumps and such.

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AmericanPowertrain · 01-07-2009, 06:40 PM

I have been reading along in this thread based on a tip from one of the moderators to get involved. Most of the information here is pretty accurate. The stock t45 and 3650 transmissions do have some pretty tough gears and shafts. However, a LOT of the small parts are not only junk, they are junk attached to more junk with junk fasteners and junk tolerances. As I have explained here before, Tremec makes great transmissions, but in Ford's never ending quest to cut cost they always take out a lot of the good stuff that Tremec wants to put in and replace it with JUNK! Your stock transmissions are rated for around 310ft-lbs of torque.

It is torque that kills transmissions, not horsepower, and dropping the trans from 4th to 3rd and hammering it is more damaging than a killer first gear launch. This is because torque multiplication dictates that the closer you get to 1:1 (4th gear) the more effective torque hits the transmission. More transmissions break in what we call a "flying mile" than in stop light drag racing because a guy will be cruising along in 4th or 5th, have a smart ass in a Camaro pull up next to him and will drop the trans a gear or two and take of like a shot.

On top of that, a high percentage of Mustangs have dragging clutches that absolutely kill the shift forks and it's all downhill from there. Firewall flex, fat cushion clutches and stretched cables cause clutches to keep rotating after your foot goes down on the clutch pedal. This causes forks to bend and break, roll pins to deform and all kinds of mayhem. Before you go out and go crazy, check your clutch actuation, make sure your firewall is not flexing and replace your OE clutch with a low or no cushion disc. We can help you fix any of these problems for less than $120.

The good news is that we can also build up to 700ft-lb versions of both transmissions, with upgrades that not only strengthen them significantly, but also improve high rpm shifting and fix a lot of the inherent issues that plague these things.

When your transmission craps the bed, DON'T PUT BACK THE SAME JUNK AND KILL IT AGAIN. Let me know, and I will arrange to build a 430ft-lb Plus or 700ft-lb Extreme for you. AP

StriderTacticaL · 01-07-2009, 07:04 PM

Thanks for taking the time AmericanPowertrain, definitely cleared some things up. I have a question though, when you said it is more damaging when we are dropping from 4th to 3rd, does this also include for instance, double clutch rev matching into 3rd for a smoother downshift?

dimebag · 01-07-2009, 07:39 PM

its hit or miss... i broke my stock one with stock power, replaced it, and so far so good, knock on wood

cliffyk · 01-08-2009, 12:44 PM

To expand a bit on AmericanPowertrain's excellent post I like to emphasise the "torque not HP" issue. Power transmission components are always rated by torque, with HP being only relevant when torque and the unit's rpm limits are being discussed.

The 3650 is rated by Tremec as being capable of handling 360 lbft of torque (the 351 quotes may be a more realistic spec for racing)--at 2000 rpm that's only 137 HP (360 * 2000 / 5252), but at 6000 rpm 360 lbft = 411 HP.

So, asking "how much HP can a transmission handle" without specifying rpm, is not really a question that can be answered without making assumptions as to the motor/engine and application...

AmericanPowertrain · 01-08-2009, 03:10 PM

Quote:

Originally Posted by StriderTacticaL

Thanks for taking the time AmericanPowertrain, definitely cleared some things up. I have a question though, when you said it is more damaging when we are dropping from 4th to 3rd, does this also include for instance, double clutch rev matching into 3rd for a smoother downshift?

This should not present any problems for the transmission per se, unless of course you suck at the process and have to practice a lot on your transmission before you get it right. If you are good at rev matching then go for it. Otherwise, practice on someone else's car!

The primary reason high torque loads (shock loads) kill transmissions is that given enough twist, the shafts inside the transmission will tend to bend away from each other. This is called ballooning and as the shafts part ways the gears tend to get a little sporty with each other. At the same time, the bearings that the shafts ride on get a ton of stress on them. You will sometimes see race transmissions with steel straps around the main case. This is to keep the transmission from ballooning under high loads.