Transmission rebuilt now engine runs rough

[Troy]

Ok, so this is for my 76 Power Wagon 440 with a 727 auto. I just had the transmission rebuilt with a few upgrades. When I took the truck to the shop it ran fine. When I picked it up it seems like the idle is really low and it wants to stall (even after it warms up). I adjusted the idle about 2 turns and it's better but still bucks and stumbles when driving (slowing down usually). I can understand if the new converter is putting more of a load on the engine but shouldn't the trans shop have made sure the thing would actually run? Is there something else that could cause this issue? Should I just reset the timing and idle since it probably needs done any way? I just don't like guessing and making a lot of changes if there could be a simple explanation.

Thanks,
Troy

[Dans 68]

What did the shop say? Common sense says that the problem happened there. I'd wait until they can explain why your truck now runs rough. 

Dan

[Cooter]

This gets back to the It never did that before you worked on it" thing...Yes, the shop COULD HAVE done something, but not likely..Most likely, the problem just happened to happen after someone touched it...Like a light bulb, you walk in the room and flick the switch, light bulb blows...Who's fault is it?, the guy that last used up all the good left in that bulb, or you the one that turned it on?

We call these types of vehicles "holy matrimony" cars/trucks, as once you touch it, you are married to it for life.

I usually tell the customer EVERYTHING the car is doing when they come to pick it up, but the shop probably didn't because if they hadda brought it to your attention, they were probably thinking your first thought would be "Well, if they told me about it, then they musta done something to it and are expecting me to "Let it ride"...When in fact, the truck just simply started acting weird because wiring was moved that haden't been moved in 20 plus years...

Perfect example of this was a Mercedes that came in the shop for a trans problem..We installed a new trans and fired the car up. The first thing I noticed was smoke coming from the tailpipes and LIQUID oil running out the pipes. The engine all of a sudden began running rough and simply blew up(V6)...

Come to find out, the thing doens't have an oil dipstick and with no way to check the oil, the guy's wife had stopped by every gas station in the area asking bout an "oil light" that was on..They simply put a quart in and sent her on her way...When the engine finally blew, we drained what was left of the oil into a 5 Gal bucket and found out it had 4 Gal of oil in it....

Was it OUR fault it blew? Of course not ,but try explaining that to the guy when we called him to tell him his car needed an engine after WE put a trans in it.....We covered it, but we didn't HAVE TO...It wasn't our fault, but sometimes you just can't argue when you can't prove the problem was there to begin with....

[Troy]

I don't really care whose fault it is - what should I be looking for to fix it? I drove it to the trans shop and it ran fine. I picked it up and it didn't. I always try to look at the last thing that changed when troubleshooting. My question is: is it possible that the new trans is "tighter" or something? If not, do I treat it just like any other time an engine isn't running right?

Troy

[greenpigs]

Did you check the vacuum? I know they shouldn't have had to mess with any of the lines but it is a easy check.

[Cooter]

As stated, I would try and see what one change at a time does. Like Timing check to even see if it is off..then, idle again. Then, move to things like maybe checking fuel filters..Then, checking for trash in carb. etc...

I doubt the truck had any kind of high stall converter, but is possible I guess.. It IS possible that the shop used a  converter that is a little tighter than the factory one, and COULD cause the truck to idle IN GEAR alot lower. Is the problem still there OUT of gear?

[Troy]

No Piggy - haven't tried troubleshooting anything yet. I've been driving it all winter but, as you know, the weather around here has been pretty nice lately (ever since it went into the trans shop actually). I'm not going to drive it "for fun" since it gets almost 7 mpg and I work 24 miles from home. I can poke around and see if anything is leaking.

It idles low(er) in Park and waaay low in gear. It stalled twice before it warmed up on the first test drive and after that I've had to goose it a little to keep it running. Since I turned the idle screw it's better but I didn't think I should have had to adjust it as far as I already have. The truck still seems to drive fine and has plenty of power - it just stumbles a little when decelerating. I have no problem just cranking on the idle screw until it runs better but I'd like to know it's necessary.

Troy

[greenpigs]

Stuck choke?

[440]

A buddy of mine had a similar problem a while back, the car would lunge or surge when downshifting. Similar to if your still on the throttle while slowing down with the brakes applied.  From what I remember there wasn't much the trans shop said they could do, that it could go away in a couple of days while it wore itself it, and if it didn't they'd take a look at it again.

I know if the vacuum modulator isn't hooked up at all or not hooked up to the right vacuum source (needs to be manifold vacuum) then it could cause erratic operation. 

I think it did go away in the end but that was a long time ago, I'd have to speak to my buddy again.

The same shop rebuilt my trans and I havn't had any issues with it.

Have you taken it back to the shop Troy and taken them for a test drive to show them the problem? 

[bull]

If it ran fine before the trans shop "fixed" it I don't see any other explanation. Too much of a coincidence. They didn't hook something back up, forgot to tighten some bolts, mounted something crooked, used a mismatched/defective/empty converter, etc. My guess is that the balance has been thrown off.

Reminds me of my trip to Yellowstone in my buddy's Ford pickup that got itself stuck in third gear on the way. Left it at an Idaho Falls trans shop while vacationing in the park and after I picked it up to drive home the front trans seal coincidentally began leaking ATF out all over the exhaust pipes. A big white cloud of smoke followed me into the rest area parking lot and I promptly called the shop owner to explain how one of the 18-year-old chimps he had working there just screwed us both over. I didn't take the whole thing too well and after a little red-faced discussion the next day the shop owner took a look and finally realized the front seal was installed crooked.

[firefighter3931]

It sounds like the new converter is tighter than the old one. 

Why was the converter changed if it went in for a trans freshen-up ? 


Ron

[Troy]

Dunno, but it's definitely got a new converter. I meant to ask when I got the estimate but it was so cheap I let it slide (shop was recommended by some local Mopar guys). By the time we got done "beefing up" the trans it was a lot more expensive and it was already together. There aren't any specs on the invoice for the converter so I assumed it was something stock - but maybe not. I'll be calling them today to see if I can get an explanation.

Troy

[firefighter3931]

Dunno, but it's definitely got a new converter. I meant to ask when I got the estimate but it was so cheap I let it slide (shop was recommended by some local Mopar guys). By the time we got done "beefing up" the trans it was a lot more expensive and it was already together. There aren't any specs on the invoice for the converter so I assumed it was something stock - but maybe not. I'll be calling them today to see if I can get an explanation.

Troy

See if you can get your old converter back.  Tell them that the new converter is lugging the engine down and causing drivability issues. 

You might be able to tune this problem with increased timing adjustments at idle and some carb tweaking.


Ron

[Troy]

Called the shop. They have no idea. He said to bring it back in and they'll check it over. They explained that there's nothing in the trans that would cause it to act that way (apparently a stuck lockup converter will do something similar but mine doesn't have anything fancy like that). I've had it back for 2 weeks so I'm pretty sure my old parts are gone.

I forgot to ask for the specs on the converter.

Troy

[firefighter3931]

Try advancing the timing to increase manifold vacuum and smooth out the ide. Use the vacuum guage and adjust for max idle vacuum then readjust the idle mixture using the vacuum guage still in place. 

Once that is done readjust the idle speed and see how it responds. 


Ron

[Troy]

I'll play with it tonight. I had it running really nice so I was just trying to figure out how it got out of whack. The trans guy said that *sometimes* the distributor can get bumped/twisted when the engine tilts - but he said with a 440 that was unlikely.

Troy

[BigBlockSam]

sounds like the converter to me . i had that problem with my superbee . the stall on the converter was to low for the cam . it idled ok in neutral but when i put it in gear . the rpm's went down a lot and wanted to stall.

[Troy]

Ok, so a little more info. I dug out my timing light and vacuum gauge. When I went to loosen the distributor it was only about finger tight! However, it was still set at 19 degrees. Adjusting for highest vacuum and whatnot it ended up at 18 degrees. The carb seemed a bit too lean down low but didn't take much adjusting. I reset the idle to about 875 where it seemed happy. Took it out for a spin and it bogs just the same (with a little popping once in a while from the right side). Halfway through I pulled over and twisted the idle screw up another 1/2 turn and it ran better. It feels like its loading up at stoplights though and it will stumble when I first release the brakes and hit the gas. I stopped by the parts store and spun it sideways when leaving the parking lot so it still has plenty of power! (76 Power Wagon 4x4 with 33x12.50 tires)

Troy

[firefighter3931]

Sounds like you're getting closer Troy 

If it's bogging that means it's going lean on the transition. If it's a holley carb that suggests that the squirter is too small and needs to be upsized. It needs more accelerator pump to overcome the bog.

What carb is on this motor ?


Ron

[Troy]

Edelbrock 600. I don't know if it's going lean - it shudders when I'm sitting still and it seems like it takes a second to recover when I let off the brake. Like I'm choking it and it has to take one big gasp before it can move again. Highly annoying. I may run it back to the trans shop tomorrow but I'm very short on time (truck is sold out of state) and I can't leave it there while they mess around with it.

Troy

[greenpigs]

What do you mean sold out of state...is your truck sold?

600 is sorta small but I don't think the size is the problem since it is mostly on the low side of the RPM.

[firefighter3931]

If this motor has any cam in it the 600 Eddy will be near impossible to dial in. The fuel curve is too conservative. Do you have another carb available...something bigger ?


Ron

[greenpigs]

I'm a long drive but I have a Eldebrock 750 you can try Troy.

[Troy]

The carb was fine before and I'm not changing it now. I think I goofed it up before - too lean because I set it the same as the one in the Charger (which was a 750). Instead of 2 turns out on the idle screw this one takes 4.5 for best vacuum (although it's only slightly better than 2 turns). It runs like a champ when it isn't in gear with the brakes on.

Yes, the truck is technically sold but the transmission going out put the deal on hold until it was fixed. The buyer drove it a while back and was happy with it so it did run perfectly fine at one point. I was losing money before the trans cost me $1,200 so I'm not throwing a carb in as well (there's a Holley 750 on my shelf).

Troy

[BigBlockSam]

tight converter

[Troy]

Before taking it to the shop this afternoon I'm going to check the RPM drop when it's in gear. Also, I don't notice a drop or stumble just by hitting the brakes so I sort of ruled out a vacuum leak from the power brakes. That's a side effect - when it bogs while I'm slowing down it also affects the braking.

Troy

[BigBlockSam]

my superbee runs great . real strong . idles at 800rpm's in neutral. nice and steady . i put my foot on the brake pedal and throw it in gear and the rpm's go to 450  . i opened up the idle screws to 4 1/2 turns and it helped but still not great . good luck Troy

[Troy]

Ok, it's fixed - although it's embarrassing to say how. Took it to the shop and we drove it around a bit. Mechanic noticed that it was "not running right" when under load. He suspected dirt in the carb and we discussed that it was low on fuel when I originally dropped it off so it may have sucked some junk off the bottom of the tank when they were running and testing it. After he checked all the transmission stuff I was satisfied and took it home. I started doing all the normal maintenance/troubleshooting stuff and noticed that the #6 plug appeared to be wobbling(!). I pulled the wire and it literally crumbled - baked from the headers I'm sure. Started checking others and found 5 bad wires and/or loose connections - a couple of the ends by the distributor would fall out with just a nudge. Swapped all wires with a set I had removed from the Challenger, checked tightness of plugs (but didn't replace them since they are the "shorty" header plugs and I didn't have any extras laying around), checked tightness of header bolts and distributor clamp bolt, made sure wires were tight and would seat correctly, and checked vacuum lines (there aren't many) for leaks. Restarted truck and the idle was obviously higher. Pulled it back down to 850 and reset timing (which was now reading differently and I have no idea why). Reset carb idle screws and reset idle speed again. Truck now pulls 18 inches of vacuum instead of 14. Got in and shifted gears - idle drops but truck doesn't stumble and surge. At that point I declared a "full stop" because it's my luck to keep messing with stuff until I make it worse or break it! Ideally I'd check the passages in the carb and replace the plugs (which I'm sure are fouled now), distributor cap, and fuel filter.

Troy

[Dans 68]

Glad it was something simple. 

Dan

[BigBlockSam]

 

[greenpigs]

Good, now get the money & buy another 68.

[Troy]

I'd like to get one on the road first! I still have two in the garage... and 2 70 Challengers and my 70 Mach 1. The purpose of selling stuff off is to concentrate on the "keepers" and get rid of the money pits that I don't really need/want.

Troy

[Kern Dog]

You deserve a pat on the back for being honest. Many egotistical guys would have never reported what you discovered. Thank you.

[firefighter3931]

It's allways the simple stuff that we overlook...been there too Troy ! 


Ron

[Troy]

I'd have looked sooner but I didn't want the trans shop to say I'd been in there messing with stuff - although there's nothing I could have changed that should have affected their work except the kickdown linkage. It's a reminder that one change can affect more than just the area you changed.

Troy