Transmission the weakest link?

[tin_tin13]

I'm looking to get in the dsm game but having my worries about the transmission holding up with the power levels. Currently have written out a 2.4long rod, 2g built head kelfords 272, Hx40 tial vband housing 1.0 a/r. I'm looking at the jacks hd transmission for now, so my question is how do I keepmyself from blowing trannies? Only thing I can think of is major weight reduction? I really don't want to look into a different platform being 2g has been one of dream builds.

 

[boost97gst]

Id take the tranny problem over any engine internal anyday . Im sure no one would disagree with that.
But to the OPs question as we are off topic(kind of): I would have to agree with whomever said an automatic is your best bet. These stock 5 speeds are unbelievably tough but with an auto your going to spend less on modifications and have greater longevity.
I never launch my car, it being a fwd and all, but if i did i couldnt see it holding up very long in completely stock form. This is a guess though.
I CAN say for sure that i have a 5 spd with unknown miles, probably high, and it has taken plenty of pulls 2nd through 3rd at 30+psi on a 5858. Thats most likely more than double the torque that it was intended to take. People have pushed much further on stock too.

 

[Archer Fabrications]

I have a shep stage 3 i dont wanna risk that or my built motor. But from my understanding if the trans gears are spinning te input shaft while clutch is in or neutral, then everything is getting lubed anyway.

 

[donniekak]

Only the input shaft spins unless the car is moving. It sits above the oil level in the trans, and relys on the front diff, center diff, and intermediate shaft spinning to throw oil on the guide, and drip onto the 5th gear assembly. The intermediate shaft cannot spin unless the center diff is spinning, which requires the car to be moving.

 

[Tyeler18]

I believe what Tim meant was, don't let it sit there and idle, then expect everything to be good to go and beat the hell out of it. Even though the ENGINE is completely warmed up, the tranny/tcase/rear end do not warm up until driven on.

OP- My best advice is don't dump the clutch. Preloading will save your transmission greatly. We made almost 700whp through a stock GVR4 trans, in a full street weight (no weight reduction) 91 GVR4. This was using the dogleg QM twin disc clutch and was able to launch the hell out of the car without destroying them. The only time one would grenade was during a launch that wasn't preloaded (IE dumping the clutch). Also, street tires that spin good will help cushion the torque that the trans sees when you launch. A dead hook is one way to kill them, so some wheel spin IS a good thing.

 

[Archer Fabrications]

I believe what Tim meant was, don't let it sit there and idle, then expect everything to be good to go and beat the hell out of it. Even though the ENGINE is completely warmed up, the tranny/tcase/rear end do not warm up until driven on.

See thats what i expected. Obviously you would take it easy until your drive train is warm also. But i simply don't believe it will damage it from a warm up to operating temp in nutral.

Eapecially following sheps instructions to over fill the trans 2.5-3qt i stead of the normal 2.3qt

 

[tkelly27]

If you aren't putting any load on the motor, then it will take even longer to warm up. You'll be running the pistons at the looser tolerances for longer allowing them to smack around for unnecessary time periods. Heat can come from combustion or from friction. If you let a car sit and idle less heat comes from combustion and more of it comes from friction. Driving a car at a steady speed with a low load is a really good way to warm it up, and also get lubrication to the drive train.

If you let a car sit at idle until the temp comes up you've done nothing for your transfer case or differential, so you'll still need to drive carefully until you get those up to temp. It's easier to know that you've gotten everything warmed up if you're rolling while you warm the engine up.


Yes, until you get a crazy expensive transmission you run the risk of popping a DSM tranny. They just have small gears and there is no way around that until you get new gears. As has been said a few times, if you are nice to it, you'll be surprised at what it will do for you. Again, as mentioned, don't be pissed off when you're putting 2-3x stock torque through it and it breaks, it wasn't ever designed for that.

 

[Archer Fabrications]

So you go and drive your car when yhe coolant temp is 85*?

 

[twicks69]

So you go and drive your car when yhe coolant temp is 85*?

Yes, why the heck wouldn't you DRIVE it??? I turn the car on, coast out of my driveway (I live on a hill) and put it in gear when I get on the street and drive to wherever I am going. I simply put it in a low gear and keep it at low rpms (i.e. 1000-3000rpm) until it is fully warmed up, then I get on with my normal driving.

As for the transmission internals; if you are physically in neutral, and the car is running with the clutch engaged (pedal up), you will only be spinning the input shaft (3rd/4th hub and slider and 5th/rev hub and slider as well) and the intermediate shaft 1st/2nd gears will be free-wheeling. The input shaft 3rd/4th/5th gears are floating and may have a bit of gear oil resistance causing them to spin, but they are essentially not moving. The intermediate shaft, center differential, output pinion shaft and front differential are also not moving. If the vehicle is physically moving in neutral, then the input shaft, 1st/2nd on the intermediate shaft, 3rd/4th and 5th on the input shaft, the intermediate shaft, the center differential, the output pinion shaft, output shaft and front differential are all spinning. The biggest concern is that the 5th gear needle bearing, 5th gear needle bearing collar, 5th gear on the input shaft, and 5th/Rev hub are all succeptable to oiling issues unless the transmission is physically in gear or you are physically moving. The 5th gear then wears into the needle bearing sleeve on the input shaft and into the 5th/Rev hub and wipes them out. If you want pictures, I have a couple trashed sets here that I can take pictures of.

This can happen to a brand new transmission or a million mile transmission. The key thing with a brand new transmission is that once it is installed properly and filled to the proper amount of gear oil, you go and drive it with very little load as soon as possible after the vehicle has been turned on. This will get the oil flowing throughout all the passageways and will dissolve the assembly lube after it gets to operating temperature and sees some mileage on it. Sitting with your vehicle stationary in neutral with a cold transmission is a great way to wreck these components.

 

[Archer Fabrications]

Thanks for the explanation, my car just runs like ass cold i usually like it to get to 150 before i leave but i guess ill be changing that to more like 100.