speedo

iTrader: (15)

What did you use for line from the Modulator in the case to the port that runs to the outside of the case. The rubber line that comes with the (transgo) kit? Or did you run a hard or better hose line?

Had mine built by my cousin that works at a trans shop and I love how fast crisp the shifts where with the vaccum modulator until I got about 150 miles on it and then it seemed to slip up to the stall speed or lock up late. He trouble shot it and ended up just putting the stock modulator solenoid back in and it worked perfect. We decided we would take care of it in the spring so I could just drive the car. He is going to build me a backup trans this winter so just trying to find out some info about the line people are using since he thinks that the cheap vaccum line sitting in trans fluid could have been the cause.

Is it common for a modulator to go out and what are the signs?

Thanks for your time

jxaxsxoxn

iTrader: (2)

Ok so your cousin works at a transmission shop and did some trouble shooting on it.
Well....what did he find out during the trouble shooting?

It's simple. Connect a line pressure gage to the tap in the case.
Connect a hand held vacuum pump to the vacuum line (or just pull it off and put it back on.)

With the engine running the line pressure should raise with low or no vacuum, it should lower with high vacuum.

A broken hose inside the pan would probably suck transmission fluid into the engine and make it smoke.

speedo

iTrader: (15)

That vaccum tester is the first thing he brought out to my place when I told him about the trans slipping...he vac tested it from the trans line to the car vaccum line and to the case and the modulator line to the in the Trans and both did hold vaccum. Running it and checking it I would have to ask since he took it back to the shop the next day and I am not sure if he did that or not.

My line to the car is clear so we knew it wasn't sucking up trans fluid. He figured it was just colapsing inside the case, that is the reason I was asking about a hard line being better. We where also concidering a leak around where the case was tapped.

Like I said he swaped out the vaccum mod for the electric mod and the trans worked fine. He checked everything before that... Shift noids, the diode that comes with the kit, line pressure was good, went through the valve body, and probably some other things that I have forgot by now, he did a good job for the first time building one for a HP LS1 car and pretty much saved me 2000$ and I sprayed 150 shot threw the shifts at the track and drove it 3 hours home. Not bad for a first time non cookie cutter 4L60 build if you ask me.

TeamTripp

Installed properly, there will be a spring in both vacuum lines (inside the pan and the one going to the booster) to prevent the line from collapsing. I have yet to see one of the modulators go bad, but that doesn't mean they don't.

Automatics

The clear outside line has a spring in it, but I have seen the spring move which allowed the line to collapse, theseby having high vacuum at the modulator, which will create a low pressure condition, which can cause a slip or slow shifts. Make sure springs extends the full length of the hose. The one inside the pan should be treated the same way. If there is a hole in the hose inside the pan, it will smoke, and will lose fluid. I have not seen a bad modulator yet.

1QUIKWS6

iTrader: (61)

Exactly! the line I first received was a clear line with spring inside. Line is supplied xtra long and needs to be trimmed before install - the line should be trimmed so that it is slightly shorter than the length of the spring inside to force the spring to be tight against fittings on each end with no gap.

The dipshit that installed my tranny the first time didn't do that. The tube was left 2 inches longer then the spring inside. Tranny was shifting very strange - finally found that in the 2 inch area where the tube was longer then the spring - the tube had collapsed in on itself due to the vacuum and the tranny was getting absolutely no real time vacuum signal at all - it only was going off the vacuum that had been trapped in the line prior to the tube collapsing and sealing itself off

So when we checked the vacuum signal at idle there actually was one - but it was a false signal due to the fact it was only the trapped vacuum. Once we drove the car with the tester on - found that the vacuum signal NEVER changed!

My tranny is a Rock-On Stg4 - Dave @ Rock-On immediately shipped me a brand new tranny to replace the one that they had screwed, free of charge - and I took it to a real installer the second time. The tranny was still functioning but he didn't have a warm fuzzy feeling about letting me keep that one after driving with basically no vacuum to modulator. He also spent a total of couple hours on the phone personally with the installer to troubleshoot the problem, installer kept trying to blame Dave for the problem - ended up I was the one that noticed the collapsed hose. Problem is with most installers - if there has to be any operation done that is not factory - they have no friggin' idea what to do...

BTW, the second hose that was supplied was still a flex hose - but of a different type and didn't need the inner spring. I personally thought a hardline would have been best - like in the 'old' days with a short length of hose at each end - but I guess it's very hard to bend something to fit the torturous path in the LS1.

speedo

iTrader: (15)

We did have the spring in the clear line from the car vaccum line to the trans, but I am not 100% he had it in the trans line. I don't think he did. He was telling me in spring of 2006 when we go back to it he wanted me to do a hard line all the way so we eliminate that as a problem.

1QUIKWS6 -what did your car do when the line would colapse?

What would a modulator do if it was bad....late shifts?

The best way to explain my deal was I would have the cruise control on going down the road at 60 when the car would call for power it would slip up about 500 rpm before catching, and it would even do it under WOT if I remeber right so the shifts where late.

1QUIKWS6

iTrader: (61)

Car drove fine for about first mile, once the hose collapsed and effectively sealed off any further vacuum signal; the tranny would shift late, and shift in & out of gear continuously - this was due to the fact that it did have some vacuum to modulator (trapped in vacuum line), but not enough to hold the tranny in gear it was supposed to be in - hence clutches were slipping.

BTW, once the hose collapsed, it never re-opened.

If modulator was bad (blown diagphram) I would assume (there's that word) that it would act as if there was no vacuum present...

speedo

iTrader: (15)

Pretty sure mine had the same deal going on as 1BADWS6

Like my cousin who did the whole build and transplant for me said he thought the line was colapsing inside the trans which it probably was since we didn't have the spring into that part of the vaccum line as Pro built posted. Just makes me wonder cause it worked great for 150 miles, unless the line in the trans without the spring was strong enough for 150 miles and then lost its density.


Thanks for the info

WeeWolf

iTrader: (16)

if the hose is collapsing could that explain why shifts are firm at say 1/2 throttle and soft at wot. if so i imagine that could cause repeated 3/4 pack being burnt?

speedo

iTrader: (15)

Talked to my cousin over the weekend. He did install the spring in the line in the case.

Just going to do a braided line to the case and a hard line in the case and see what happens in the spring.

cablebandit

iTrader: (37)

Dave sent me a different type hose for mine and never had a problem out of it. It was much thicker and still had a spring. Glad you got your problem fixed. Sux Dave had to eat a tranny because of an installer. This happens too many times. Builders get blamed for bad tunes/installs. This also gets them behind on their scheduled work trying to fix someone elses screw-ups. Those hoses get HOT...F-body engine compartments get really heated and make hoses weak. I deal with this a lot because of all the hoses on my car from the turbos...alky injection etc

Hotrodhawk

iTrader: (1)

wouldn't lack of vaccume just cause full applie pressure, all the time?

Automatics

At an idle with low vacuum, the pressure will be higher than if there is a high vacuum condition. But, remember that with a big cam, that once you start to accelerate, you start to produce good vacuum quickly. The same thing happens when you run a TH400, and there have not been problems with the modulator setup, causing a higher than normal pressure at an idle, because of running a big cam.