73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: devanray on February 24, 2011, 06:02:32 pm
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I have just purchased a '77 C-10 and am trying to get this safely on the road. My laundry list grows daily but I'll start off with my biggest concern.
She will shift from 1st to 2nd and then 3rd very fast and after that the RPMs just roar with little power. I have tracked this down to being tranny connection issue. Now, I've been told that I need a detent cable that will connect to the throttle bracket on my QuadJet, and others say that it an electrical switch that sits by the gas pedal some say adjust or get a new modulator. What should I do first??
When I figure out how to get pics on-line I will do that.
All right, any takers?
Any direction or help would be so appreciated. BTW, none of this is original, I saved this girl from a backyard (bailing wire and duct tape mechanic) he really didn't know what he was doing, sad to say, neither do I. But I plan on doing it right!
Thanks all!
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Vile I am sure or someone else will ask you more questions, but for now do a search in this section for " detent " and it will pull up 3 pages of previous post and you might get your answere, or at least know what kind of questions everyone is going to ask you. Good luck and Welcome to the site from California.
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Thanks!
I've been reading those posts and think I'm getting a bit closer to narrowing things down, but still am not sure if it's a cable to the carb or the wire to the transmission switch by the pedal that is supposed to be on this rig.
I'll figure it out either through these previous posts or this one, this site is fantastic for information and just plain nice folk.
Thanks again
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TH400 correct? There is no Detent cable. So your 1-2 shift is fine, 2-3 shift is early then slip correct?
You have checked the fluid with the engine running at operating temp right? What's the level and condition?
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Yea but it could be something to do with the pedal switch that makes it down shift right?
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It's not the detent solenoid if that's what you're getting at.
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The fluid is clean/spread evenly on a paper towel as it should, running ant normal temp in park, no high temp indications on the dipstick and the pan only had minor debris, very standard in my experience.
When the TH400 hits 3rd it seems to stay there, not slipping really, just hits it and the rmps go up, no tach so I can't give specifics. Also, when I shift (on the tree) it stays in N when I have it in D, the lever goes into the "indent" as it should but doesn't shift until I bring it into L2, than if I bring it back to D it stays in D (3rdgear), not sure if this means anything or not. Also, the linkage is loose, I'll check the shifting tomorrow, bought a Chilton manual so It should help a bit with making sure the shift linkage is doing as it is supposed to.
No detent cable, sweet, one thing off the list, It must be the pedal switch. I'll read up on the tranny switch and see what is needed, it hooks up to a solenoid right? And there is no modulator?
Thanks for your help, I've made it farther in the past few hours than I have in the past few days.
It's not the detent solenoid if that's what you're getting at.
This solenoid attaches to the transmission pedal switch right?
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The TH400 has a modulator, no selinoid that I am aware of.
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The 400 has a detent solenoid which is electronically controlled. It has a vacuum modulator and a governor valve. These all control shift points however if it's slipping in 3rd it's probably time for an overhaul.
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Okay, got some pics and labeled them as best as I could with Vile's information.
The governor valve I have seen taken out of the tranny but can't figure out from where. What does it look like in the tranny? I'l read more on this unit to figure out what it connects to and such.
The 400 has a detent solenoid which is electronically controlled. It has a vacuum modulator and a governor valve. These all control shift points however if it's slipping in 3rd it's probably time for an overhaul.
The solenoid is electronically controlled by the transmission control switch, right? I would hate to think that the tranny is just shot, I'm willing to get everything hooked up as it should first and then see what happens. Should I not be driving this rig around until I get that control switch hooked up?
Am I learning anything or am I just walking backwards, eyes closed and chewing bubblegum? javascript:void(0);
Thanks again all!
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Your pix are correct, unfortunately the detent solenoid is for forced downshifts and would not be the problem. The modulator delays an upshift or forces a downshift based on engine load. The governor is road speed, the faster you go the higher the pressure. When governor pressure is higher than modulator pressure it forces an upshift. This is all control which doesn't sound like your problem if it's slipping in third.
Do you have access to a transmission oil pressure gauge?
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:'( No, but I will see about renting/getting one. I'll get the results up for you as soon as I can.
Edit: I do actually have a oil pressure gauge but like most things on this truck, it isn't hooked up. I'm looking into the connections now.
How much should I expect a rebuild to cost? I know it varies depending on the parts needing to be replaced, but what should I expect, if I have to go this route and would it really be worth it?
Thanks, I'll get the pressure reading as soon as I can.
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Update:
So, getting the oil pressure may take some time, but today I had worked on the linkage and put in some new rubber tubing from the modulator steel tubbing to the intake (riser on carb). It seems to behave better than before, perhaps it is my imagination. The gear selector is still off and I will continue to work on that, still can't find a gas pedal transmission switch (not the cause but I want to see if it works and have everything hooked up properly before I spend big $$ on the tranny). Still seems to be at a high RPM in drive but the shifting seems to be spaced out farther as I would expect it to be.
I'll put new plugs in on Monday and tune her up a bit, just to make sure that it is 'all good under the hood'.
Would getting an RPM gauge assist with the diagnoses? Could you also describe to me what you mean by "slipping in third", just want to make sure we are on the same page. Also, is there some sort of 'koodos' button or someway to acknowledge your assistance with this Vile? Either way, thank you for your time and everyone else who has or will chime in. I'm doing my best to get around to other posts and see if I can help, but as of yet, my knowledge level isn't as high as most. If you have a question about a slant six in a '70 Duster, I'm your man!
Thanks again
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OK so now it sounds like you are just saying your RPM's are high in 3rd gear.... Let's hit the reset button here so we can get on the same page. Fix and adjust your sloppy linkage. AS far as the prindl gauge that's easy, just move the clip on the steering column jacket so it lines up correctly. The detent switch is here http://www.americanclassic.com/Google_Base_HTML_Pages/EL870NOS-1974.htm
If you manually shift 1st to 2nd, 2nd to 3rd do you have all forward gears with no slipping?
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if you mean by 'slip' that it actually falls out of gear, back into second or high rpm and zero power, than no, it doesn't slip. Just high rpms but still stays in third with decent power.
Man, there it is, thanks for the link!! :-*
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What's your final drive ratio? It's only a 3 speed so if you have 3.73's you're going to be well over 3k cruising.
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Drive ratio, had to look that one up. I found this and figured out what it all meant,
"To find out gear ratio without removing the cover: Jack up one rear wheel, mark the drum to backing plate with soap stone or equivilent, mark the pinion flange and housing. Turn the jacked up tire/wheel, 2 full revolutions using the marks to line up, while doing this, count the number of revolutions that the driveline makes and this will give you the ratio."
so when I follow these instructions and arrive at the ratio (i'm going to get a tach set up as well), I'll let you know the details, probably won't happen until Tuesday though.
3k is a pretty high rpm for me, so maybe all is okay, just not used to it. She should have more power though, once I get the girl tuned and the kickdown/tranny switch in, I'll see what she can do.
Thanks again and talk with you on tuesday.
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Okay, I've calculated that the ratio is approx 3.5, that is with the 'spinning of the drive line with the wheels up' technique (not sure if it worked really), the tach reads 2K at 40mph (around). So the RPMs don't seem to high but still for a 350 it should have more power than I am getting, and she is very noisy (could be that the hack who owned it before me welded the fan to the shaft so it spins insanely fast! This guy, I tell ya) going to replace with duel electric soon.
I've ordered the kickdown (tranny switch) for full throttle acceleration and I will be tuning (new plugs, fuel/air, idle) the engine tomorrow or Thursday, I'll also get the shifter aligned correctly.
Now... when I had put the tach in (super easy!) I had taken the HEI (?) dist cap off to plug in the tach. After which the engine had some serious issues starting, I would nearly have to flood the engine to get her to start, then it would "booh, booh, booh" (low rumble, low idle) and than kick in, once it fired up no prob. Did I do something when I took the cap off? Plug wires are in the same spot and secure, no damage to the rotor thingy, is it just a weird coincidence or can you fudge things up by taking the cap off?
If you have a sec, look at the pic and tell me what you think. Are two chokes hooked up to the carb and just the electric isn't plugged in? Where should it plug into if at all?
If I could, I'd send ya some steaks from the Kansas City Steak Company, talk about good eats, don't eat meat anymore myself, miss this stuff :(
By the way, my truck passed inspection today so now I can get it registered and be legal!!! (side note: we are the same age, how do you know so much?)
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Devon, Your item in the Red circle is the elec. choke assy. It should have a One wire 12v hookup...a odd looking (big, considering it's only One wire) plastic plug. Right now your choke is closed, if it was hooked up & working properly, the front plate on top would open up pretty much straight up & down once the engine was warm...you need to get that working correctly.
The item in the Green circle is the vacuum pull-off. To see that it is functioning correctly, take the hose off of the carb...push the flat arm part inward toward the round part & hold your thumb over the hose, now let go of the flat arm...if it stays in until you remove your thumb it is good. If it springs back out while your holding your thumb over the hose...either the hose is bad or the pull-off is. It makes the secondary air flap not open too fast (that's where the linkage is going). The pull-off should suck in slightly on start up also.
One thing I see in your pic. that concerns me is the big vacuum port that is open on the far Right of your pic. Do you normally have a hose or plug on it? Good Luck, Lorne
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I am pretty certain that is fuel vent, it used to run to the coal canister. Im 99% sure.
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I think it did go to the canister as well, I felt no vacuum on it before so didn't think anything of it, I now have it capped. Thanks for pointing that out, Haulin It, I'll test the choke and the vacuum pull-off tomorrow and post results.
The automatic choke now has keyed 12volt from the old electric oil pressure harness which is also feeding keyed power to my new electric rad fan.
The fan mas made the hood noise while driving drop dramatically and the horsepower has increased by an amazing amount, I smoked the tires by accident when I took her for a test spin to the grocery store. Now I don't know if the extra horsepower is from the choke having juice or getting rid of that welded fan. I recommend this 'upgrade' to everyone, easy install, all for less than $90 bucks, more horsepower, more MPG and more room under the hood, I love it! She comes on @ 185 degrees and you can even hook up a switch to turn it on manually, I didn't get the adjustable because I would have set it at 185 degrees anyways.
Now, however, I am noticing an oil leak by the dip stick, reading other posts I think that there is too much pressure, I will test the PCV valve tomorrow. Another thing is going back to its shifting issues, it seems to shift a little better, more accurate, but it jerks a bit from 1st to 2nd. One problem fixed brings new ones to light (or just sheds more light on old ones).
Still haven't tuned her yet but that shouldn't have anything to do with the jerky shifting.
So, are 2K RPM @ 40MPH (third gear) and 700 RPM at idle good numbers?
Thanks again everyone, I can't believe how much I've learned over just the past few days from everyone here (and how much I've saved in mechanic bills!). I always want to repay so I try to give my 2 cents in other posts and by tomorrow night you should see that I have payed my dues ("member") to this site, but just know its my way of saying thank you to all of you, especially Vile, who takes his time to help as many people as he can, from problem to resolution and who has helped me so much thus far.
Whooo, I think I've had to much wine.... :P
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Issue has been resolved, subject line no longer relates to issues -- PLEASE DELETE POST
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We don't delete posts, just start another one.