Anybody Need This

[icanfixall]

http://cgi.ebay.com/ebaymotors/ws/e...30282530931&ssPageName=ADME:B:WNA:MOTORS:1123
I think this is for the C6 trans... Looks like a great spare part....

 

[Cheaper Jeeper]

Yup, looks like a VRV (vacuum regulating valve) to me. Definitely a good thing to have on hand if you have a C6. If yours goes bad the C6 pretty much no-worky no more...

 

[smokin69]

Mine went bad and I just put the lines together and it actually works better than before it went bad

 

[LCAM-01XA]

IIRC the diesel C6 works exactly like the gasser C6 - high vacuum at the modulator is read as light load and results in low line pressure, little to no vacuum is interpreted as a WOT or high load condition and the line pressure goes up. Smokin69, by connecting the two hoses together you are now feeding your transmission full vacuum, so whenever you increase the load on your drivetrain (by offroading or towing or just plain hauling away from a traffic light) your transmission will not respond increase the line pressure to match the load - do you ever feel like your transmission is slipping?

 

[smokin69]

Not really, it runs faster now than it did before and shifts a lot better than before as well, not as hard of ***** and I don't have to drive full throttle anymore. I got a new one of them regulator things and it didn't change it any different than before so I just hooked em back together.

 

[LCAM-01XA]

Hmm, the new VRV wouldn't have made a difference if you adjusted it like the old one and the old one wasn't bad to begin with. The shift points are adjustable through the vacuum modulator on the trans too, so it is possible someone who owned the truck before you had that maxed out so even while the VRV was working properly it just couldn't overpower the modulator - as in, now even the full vacuum applied to the modulator is translated to the trans valve body as part throttle and medium-load condition, resulting in decent line pressure and that nice shift schedule you're seeing... Question - when you get on the throttle (but not floor it), does the trans shift later? Try it, it should shift fairly early (as low as 14-1500 rpms) under light throttle, and past 2000 when you're into it, that's the proper behavior - however, if you floor the pedal then the kickdown linkage takes over and negates all input from the vacuum circuit, so when playing with the shift points avoid the full throttle situation.

 

[smokin69]

Well the truck doesn't run right now, but it did shift right about like that before. My kick down linkage doesn't work so when I floored it before and after it would just go in whatever gear it was. I was kind of suprised because I can actually pull hills better now with it like it is than before, it feels more like a newer truck where it will rev and actually get into the power instead of before where it felt almost like it was locked directly in and it took a long time to get the revs up once it shifted with anything less than full throttle

 

[LCAM-01XA]

Well the truck doesn't run right now, but it did shift right about like that before. My kick down linkage doesn't work so when I floored it before and after it would just go in whatever gear it was.

So your truck, when it ran, and with the vacuum hoses connected straight, the trans would change shift points according to throttle position, and it would also kickdown when you mash the pedal to the floor? Well that's one posessed C6, that's for sure, as without the VRV it's supposed to shift the same no matter how much heat you give it, and without the hard linkage and the VRV it shouldn't kickdown either.

I was kind of suprised because I can actually pull hills better now with it like it is than before, it feels more like a newer truck where it will rev and actually get into the power instead of before where it felt almost like it was locked directly in and it took a long time to get the revs up once it shifted with anything less than full throttle

I have an E4OD with the locking converter, I have no problem building up speed and winding the engine up even with the converter locked in - something else must have been going on before you do your hose thing... I know the TH350 has a some sort of limp-mode feature built in the valve body, I recall reading about it acting something like what you describe when it loses all vacuum to the modulator and the kickdown ain't where it should be, maybe the C6 has something similar and with the misadjusted modulator and missing kickdown linkage it would just stay in 2nd gear? Do you remember seeing all 3 gears (2 upshifts, 1-2 and 2-3) from your C6 before you connected the hoses straight?

 

[smokin69]

I meant without the kickdown linkage, it just runs in whatever gear its in when I floor it, not that it automatically downshifts. I have become adapted to manually shifting it and I like it just fine because about the only time it won't shift right away is if I try to go to first while at like 25-30 cuz its a little fast. I used to have to rev it out in every gear to get it to shift. Yes, I had all three gears, otherwise id have been limited to about 50 mph, and my trucks been known to go twice that fast down long straight backroads at night the old girl is faster on the top end then my 93 F150 with a 5.0 and E4OD

 

[Cheaper Jeeper]

Not really, it runs faster now than it did before and shifts a lot better than before as well, not as hard of shifts and I don't have to drive full throttle anymore. I got a new one of them regulator things and it didn't change it any different than before so I just hooked em back together.

Like MSLC said, one of the most important functions of the VRV is to control the shift points. Connected to a properly operating vacuum modulator it will "hold" a gear longer under light to medium throttle (due to vacuum) then shift at a slightly higher RPM and shift a little more firmly.

When you say that yours "shifts a lot better than before as well, not as hard of shifts and I don't have to drive full throttle anymore" what you are actually telling us is that it shifts at lower RPMs and does a soft (slipping) shift.

While that may make it feel "nicer" to drive, it is VERY ******* the tranny and will burn it up in pretty short order. Because of the torque of the diesel those soft shifts mean the tranny is slipping more than it should during shifting and that will wear out the friction material in the tranny's clutches. Better get that fixed and properly adjusted ASAP if you don't want to be replacing it soon.

When adjusted right, under light to medium throttle, the tranny won't shift until it gets somewhere up into the 2000-2200 RPMs range, and when it does shift it will shift a little hard - with a little bit of a "jerk". What I always did - and you have to develop a feel for it with your truck - is lift my throttle foot part way for about a half a second just before the shift, then as soon as it shifted I'd be back into the throttle.

When you get good at it and develop a habit of it, the "lift to shift" throttle technique makes for nice smooth shifts (no jerkiness) but the tranny still makes a quick, sharp, upshift with no slipping.

 

[smokin69]

Im swapping in a T-19 from my parts truck along with it's engine when I pull my 86 out of storage in our barn and finally get it running, but it's gonna be a while so I'm not to worried about it. Im also just gonna go with a divorced 205 instead of switching to a 4x4 trans.

 

[oldmisterbill]

Anyone with a C6 should bid on it-what a great part to heve for cheap on your spare parts shelf.

 

[LCAM-01XA]

When adjusted right, under light to medium throttle, the tranny won't shift until it gets somewhere up into the 2000-2200 RPMs range, and when it does shift it will shift a little hard - with a little bit of a "jerk". What I always did - and you have to develop a feel for it with your truck - is lift my throttle foot part way for about a half a second just before the shift, then as soon as it shifted I'd be back into the throttle.

That's exactly what I do, I always shift with my right foot, don't need no stinky clutch for that Great way to prolong the trans life too, taking off the load on the clutches while shifting.

 

[Cheaper Jeeper]

That's exactly what I do, I always shift with my right foot, don't need no stinky clutch for that Great way to prolong the trans life too, taking off the load on the clutches while shifting.

Yupp-ers, for sure.

I do the same with my old Mecedes. It needs a bit of tweaking and tuning so it has a case of "afterburner" (slow accel until the boost starts building then WHOA NELLIE). Tends to make the 1-2 shift pretty hard.

So until I get around to (and decent weather for) tweaking and tuning, I'm shifting with my right foot too...

 

[big van]

That was a great price for that VRV! I hope someone got it.

Smokin 69- if you run with the lines hooked together the way you have them your tranny will burn up quick. The vac. needs to be regulated for a purpose.