Having some trouble with line pressure in my 4L60E after a fresh rebuild.Maybe someone on here could help me out?At WOT I have a very respectable 230 PSI but if I hold it to the floor for about a mile or so the pressure slowly drops off down to around 160-170 PSI. Does anyone know what would cause this? Also I was told that if you put it in reverse you should have full pressure (like 300 PSI) Don't know if this is true but mine only has 75 PSI at idle in reverse.Whats going on here? I do have alot of good highperformance stuff added in the tranny to make it stronger and my builder has been doing tranny's for 25+ years(also works for GM)I guess we are kind've stumped right now. I do have some other issues with the new converter I put in put we don't think it has anything to do with the line pressure. Anyone with any ideas?Thanks Traver

 

Year, make, and model would help a little.....

 

Sorry about that! It's a 2001 TransAm WS6.

 

Without knowing what your builder has done it's awfully hard to tell, heres a shot in the dark. The high pressure loss at wot could be pump cavitation, or high pressure crossleaking. As far as the reverse goes it looks as tho you aren't getting any reverse boost....stuck boost valve? Hope this helps ...Dave

 

I have the 10 vane pump with the billet rotar,high pressure regulator spring.Also I have installed a 4th gear super servo and extra cluthes. Transgo shift kit has been installed with the three washer setup.Anything else you would need to know?

 

Everything you listed is good....alittle overkill on the super servo(imo), but still not bad. Do you know if the slider has been staked? this could be your problem...even at wide open throttle your going to have some pressure drop off..this is normal now if your gage is off ten pounds you may not have a problem. I think the biggest problem is no reverse boost....generally speaking you should have twice the pressure in reverse as you do in drive ...@ idle you'll have say 70 psi in drive ,in reverse you should have 140...or there abouts. Spiking up to say 300...275....range. I hope this helps ...Dave

 

How are you measuring the line Pressure?

 

Dave..........do you mean staked, as in the high pressure spring has been pinned so to speak, so that it can only come back or return so far at high RPMS. If this is what you are asking about then yes we did do this because it came in the high pressure pump and spring kit. I agree on the overkill(same thing my builder said)but I plan on putting it behind a 427 next year and want it to be up to the task.I know you believe in the vacumn modulation since I've seen you talk about it many times, but my builder and alot of others I discussed this with felt that this was going backwards in the way of doing things. To each his own I guess? I really do appreciate your comments and ideas Dave. It's nice to know someone will try to help when they can.I just build engines and I stay away from the tranny end because I have no clue how they work.We're starting to think we have a bad boost valve or something to that effect. My builder said he installed the one that came with the shift kit and we are going to start by reinstalling the factory one just to see what happens.Anyways, thanks again and keep all your ideas coming.I'd like to drive this thing yet this year before the snow flys up here!

 

Hand held hose and gauge out of the port on the passenger side of the tranny. Traver

 

Oh ya............one more thing I forgot to mention. The trans is also leaking a little bit out of the vent tube. After driving it for awhile and then parking it I will get a spot about the size of a 50 cent piece underneath my vent hose that is hooked to my tork arm. It's not much but there shouldn't be any! Traver

 

In light of the fact that you are electronicly modulated this is an okay pressure...it'll drop 40-60 lbs....commanded by the puter...where you get into trouble is when you spike the throttle up there on the top side....Hell we burned one up with 180 psi doing a forced downshift @70 mph...funnier than **** it went from 180,down to 80 bounced around down there then spiked to 230....by the time it hit 230 the 3/4 was fried..I'd just pull that good steel transgo boost valve clean it and pop it back in . My guys sometimes get the shim wedged in there..in the bore. I'm not sure how they do that...i'm begining to think they do it to watch me go off... Didn't mean to ramble, good luck... thanks for the kind words...I hope I helped...Dave

 

Still haven't come up with any solution yet. Hopefully we can figure it out soon!Any other ideas out there? Traver

 

Update.....Now I have a code P0757(shift silonoid B stuck)in my codes about 5 logs.Just was waundering if this could be some of my problem.Also I noticed I am running very high temps for not running through the radiator(200 ish cruising) Still can't figure out this issue. Any help would be appreciated. Thanks Traver