If you hadn't heard, I blew my 3 day old "built" 4L65 trans.

Just got word back today that it was the stock GM 5-gear planetary (1st gear sprague) that blew up. Evidently, power braking at 4psi of boost is "way too much power for that part". So the Tune will have to be set with basically no timing when brake-stalling. This will of course decrease my power off launch, but Mike (the Tuner at Xtreme) said a 2-step is set up similar. Evidently once I hit 1mph all the timing will be put back in. Sounds a bit goofy to me but if it works and doesn't smoke the trans, great.

It just bugs me that there is NO trans built to launch with gobs of power that will work in my truck. You spend all that money for a beefed up trans then have to adjust the tune to make less power.

 

that doesn't sound right, how much hp should the build trans support?

 

Good question. Most pieces I've read is that they should hold 500aw or rwhp without much trouble. But that's walking a fine line. I'm around 470hp/520tq, and at 4psi, I would think it wouldn't even be near 400hp. I've heard/read WAY too many stories of these "built" 4l60's and 4l65's blowing. I understand there isn't an aftermarket or built 5-gear planetary to replace the stocker. Sounds like the weak point...

 

too bad man, I hope you tuner can fix ya up.

 

I think you might have just got a bad part. I've launched LOTS of times with my 3800 stall, ripping all 4 tires loose. Quite a few 1.7 60' times on my FLP level 4 with the 5 pinion planet.

What kind of 60' times does your truck pull?

 

Maybe it was a bad part,chances are the shop wouldnt admit a they did something wrong,time will tell on this next time on how good a job they did.Look how many 12 second SS trucks there are with a shift kit and servos, they are holding up really well.My buddys yukon denali that we H&C headers stall,he's running close to the times you do and his trans has been holding.

 

I've heard alot that a trans's strength is 80% builder and 20% parts.

 

There is no black magic to to,get the best parts,set the correct clearences and do a clean job,very few tricks are not shared among builders seriouse about there work.

 

i've broken one of them before. there is a huge difference in the quality of the bunch though. there are cast steel versions, cast iron, and billet steel. i'd be guessing that your 5 pinioin planetary that broke was an aftermarket replacement for the gm part. there is no reason you can't launch it under the power levels you've put it to so far. look at the 60' time big tex pulled with his 65E. that's alot of stress and a damn heavy truck. i'd be asking to see the part. the 5 pinion in the picture is a factory gm 65E that went in place of the cast 4 pinion i pulled out. the 5 pinion was a much harder machined steel.

 

I've read the same thing. There are definately different grades of 5-pinion planets. The weakest being weaker than the stock 4 pinion part.