Tranny go Boom!

**richard head** · 10-17-2007, 09:04 AM

Yeah, huge drag. Getting an estimate on it today, it wasn't totally fried but definitely grinding and whatnot so it's real shitty. Anyway, is it possible that overly aggressive HPTuners settings are to blame? If the shift pressure is too high, can it damage some kind of seal or something? I used the performance mode table to decide how to tune my shift pressure, I guess that was a bad idea though. It seemed like about 40 was the most that really made any difference, I had it set at max for top torque and it didn't seem to shift that much harder than the places where it was at 40 or so. Keep in mind this was a 150k tranny, so it was bound to happen pretty soon anyway, but if this was a big part of why it went out now as opposed to later then I will be doing some editing on my tune. What do you guys think?

**Frost** · 10-17-2007, 12:12 PM

post the tune

**edcmat-l1** · 10-17-2007, 01:43 PM

I've never run into an issue with higher pressures causing a trans failure.
We build, or have our tranny guy build, a couple dozen 4L60Es a year. I tune them pretty aggressively.
Higher pressure, and quicker shift times means less time for clutches and bands to be slipping. I've went over this time and time again with our builder and he assures me, and it makes sense, that its not hurting, on the contrary its probably helping the life of the trans.

**Frost** · 10-17-2007, 02:02 PM

I had a built 4l60e (shift kit in it already) with the (max) line pressure set at 95psi push fluid through a seal in the back on the dyno here at PAS. After getting him to lower max pressure in the PCM to 92psi on the third pull, it stopped pushing. The guy is a buddy of mine, and I know it hasn't been leaking since that. If it wasn't pressure, I don't know what to attribute it to?

After going through what tables were available with a guy who built some trannies for us that were serious business, he told me ok to work shift times, I have a different force motor current table that I use, but he had me leave the max line pressure at 90 and the pressure tables (pressure vs. delivered trans torque) stock, saying that valve body modifications allowed for improved pressure themselves. Shift times were set at .250 to disable adaption.

I should get my guy and you get your guy, and they should fight!

**edcmat-l1** · 10-17-2007, 02:36 PM

Originally Posted by Frost

I should get my guy and you get your guy, and they should fight!

I bet my tranny guy can beat up your tranny guy!!!!

Seriously, the line pressure thing I guess I shoulda been more specific. He told me, and I go by what he tells me, that upping the line pressure is OK in a stock tranny, actually helps it. In a built tranny, with a shift kit, I do use the stock pressure settings.

**0rion** · 10-17-2007, 11:49 PM

I'll take a little different angle.

At 150k your tranny was on borrowed time. The stock tune probably would've broke that tranny.

**richard head** · 10-20-2007, 05:49 PM

ROFL... you guys aren't gonna believe this. I had decided that it was low when it started slipping on the highway, assuming a leak somewhere. I, for this reason, had been adding little bits whenever it would start slipping all day. Had the car towed to the shop, and the shop called and said it was overfull but running fine. They did a tranny service on it, and 156k and all it still does an excellent job. I bumped the 90 pressure down to the 320 in HPTuners and now she'll bark the shit out of the tires during any shift and it hasn't even slipped since the service was done. :rofl: $300 bucks, and 250 of that was the tow!

I think these cars are amazing, I have seen them do extremely well as far as durability goes over the years. The 3800 I had before the T/A was ridiculous, stock engine and tranny at 160k were getting sprayed 125 through shifts and all at the drag strip and I never felt that thing slip even the slightest bit.