So in March my tranny gave up the ghost right in front of the dodge stealership 60 miles away from home, so I pulled in to be told that it's dead and needs a re-manufactured transmission installed (overheated, the dang transmission check-valve got me before I had a chance to bypass it). So after taking a month to gather the funds, I finally get my truck back, but now I notice that when ever I accelerate, my HVAC goes from vent to defrost, it didn't do that before Dodge had it.. I used the nifty search button, and discovered that this indicated a vacuum leak somewhere in the system. I took it back to the dealership that did the work and told them that it was a new problem since I got the truck back and they had the mechanic who installed the transmission came out and spent about 0.3 seconds looking in the engine compartment and said that I needed to buy a vacuum harness for $12.50 as a little check valve get stuck, and that it's unrelated to the transmission repair. I buy the harness and it gets drop shipped to my house a few days later and I swap them out. I call up the dealership and tell them that it didn't work, and they tell me that the mechanic didn't do anything that would compromise the vacuum system (even though I saw the transfer case and transmission out of the truck, which I imagine involves removing a vacuum line or two), and if I want them to look into it any further, it wouldn't be covered under the warranty with the new tranny and I'd have to pay them a diagnostics fee to find the problem.

This problem has been getting worse, it used to only switch when going up a steep hill, but now I get it when I accelerating on flat land or climbing a small hill, and now it feels like the truck is loosing more and more power, it's gutless when climbing hills, and I'm starting to get hard shifts, as well as the transmission not kicking out of overdrive when hill climbing when using cruise control, it'll go from 70mph to 48mph in overdrive on cruise struggling to go up a mountain, now I turn off the overdrive as I start to climb, just to maintain speed. I struggled to pull my small trailer with my 500lb motorcycle on it the other day going up small hills. I'm not convinced that the mechanic didn't forget to reconnect a vacuum line somewhere, and that's causing maybe some of this. So is there a vacuum line hiding somewhere that I can just go reconnect?

I have tested cruise control and 4x4 and it does seem to be working, at least it got me unstuck from a mudhole..

 

Check on front of transmission, I believe there are 2 vacuum lines that plug in there. Had same symtoms wjth my 1998 ram sport 1500 4x4. Definitely a vacuum problem.

 

There are two check valves.... passenger side before the they go into firewall....you might try flipping them other direction for flow, as the the dealership was being straight with you. Search wild vents here. as for hard shift, the TV cable may need adjusting,had to adjust mine after rebuild. And no power...hate to say it but,check out the end all plenum sticky at top. Also only other vac line is for cruise control ...runs over under battery tray. No vac lines going to tranny.

 

Yeah, I read a thread about the check valves and wild vents. I'm off to dodge to pick up a few, then to napa for a pcv valve. I was convinced the dealership wasn't being square with me.. I'm almost positive the plenum is blown, just need to get the money together to have the shop replace it (not comfortable going that deep into my engine).

 

sorry, but stealer is correct, there are no vac lines involved in a transmission change. our transmissions don't use vacuum operated controls any more.

your vent issue is a vac leak or check valve. i think there is more than one check valve on passenger side

 

Cool. The guy that came out and said he did my transmission seemed kinda shady, so I had a hard time believing him. I ordered some check valves and replaced the pcv valve today, as I saw that was causing someones problems in another thread, the vents didn't go all wonky on the test drive, so maybe it's fixed.

 

So I replaced the PCV Valve on Friday and everything has been great until my drive today, the wild vents started again.... I know about the T check valve on the passenger side, as I've replaced that. Where else should I be looking?

 

on my 99 there are two check valves , one is at a t-branch, where one vac line goes over under the battery tray, this is kind of close to the #8 injector. The other line from there goes to another T, this is where the second check valve is. Also it's recommended to get pcv from dealer, for proper flow.