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1979 Chevy Blazer having weird drivetrain issues!


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My79blazer
New User

Dec 6, 2019, 9:41 PM

Post #1 of 8 (698 views)
1979 Chevy Blazer having weird drivetrain issues! Sign In

Little info first. Bought this 1979 Chevy K5 Blazer as a toy about year ago. It has a 350 with Dart Iron Eagle heads, quadrajet carb, 350turbo tranny with a NP 203 transfer case with the part-time conversion sitting on 36's and a 4" lift. It had some engine issues ( a lifter needed replaced general tune up needed) so I parked it to tinker on when I felt like it. Daily driver got repo-ed so I did the work to make it my daily driver about a month and a half ago.

So about 2 weeks ago I was leaving the store and when I shifted from reverse to drive there was a quick ( about a sec) but loud grind noise. I assumed it was my transfer case. I only lived about 6-7 blocks ( which it drove with absolutely no noise or problems) so as soon as I got home I checked my trans fluid which was fine.

There was a small puddle of what looked like engine oil next morning (which it does leak oil a bit from around the timing chain gasket) so I didn't think anything about it.
I continued driving it like normal (small trips of usually less than a few miles) and it would occasionally make that small grinding it always shifting from reverse to drive.

Here lies the true problem. I went to make a quick run to grab something to eat and got about a block from my house when it suddenly made a small grinding noise and acted like I stomped on the brakes. Besides completely freaking out my 15year old, I let it coast a bit gave it a little gas and it started forward like normal, for about 25-50 feet before doing it again. Thought it must be my transfer case that was leaking and out of fluid.
Best way to explain it is like I shifted the transfer case from Hi to Low.
So I put it in 4wd, locked the hubs and limped it home with no change. Pulled the plug on the transfer case to check the fluid level and it's still full.

The transmission doesn't have a history of shifting rough or late, have whinning noises or anything other than the usual "Chevy hard shift into gear" that every chevy I ever owned did.

Really scratching my head here on whats going on but hope someone here can point me in the right direction.


My79blazer
New User

Dec 7, 2019, 2:57 PM

Post #2 of 8 (654 views)
Re: 1979 Chevy Blazer having weird drivetrain issues! Sign In

°Update° did a transmission filter and fluid replacement as well as replaced the modulator today and checked all vacuum lines and did a visual inspection the flex plate without removing the transmission or anything and everything looked fine. Found a small vacuum leak and repaired it ( truck idles a lot smoother cold now) but when I test drove it I got 2 driveways away before grinding and slowing down again. Gonna check the governor and see about borrowing a pair of stands with a higher setting to check the differentials and unhook and reinstall the transfer case shift linkage tomorrow but I am not holding out much hope.

Just figures that I might need a tranny rebuild but the kids Christmas comes first so I might be borrowing rides until after the new year if I cant figure this out.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 7, 2019, 5:14 PM

Post #3 of 8 (633 views)
Re: 1979 Chevy Blazer having weird drivetrain issues! Sign In

You have quite the list of problems with this IDK if just trans work alone is going to get you a daily driver out of this thing? Site has a trans specialist hope he's by soon shed some light on just those things.
Not my game if the lift? I also don't know of Chevy hard shifting on any TH350 or any other for that matter the lift may have moused that up?
Did you find and know what made the oil puddle? Just curious that in a couple blocks of drive time you think is timing chain cover gasket more likely the front seal is doable with gasket set is short bucks just the time.


Trouble is it could mean there's lots more wrong than that but seems it did just sit for a long time IDK?


How about looking for another, simpler vehicle less issues than this definitely is going to cost still IDK if a daily driver for it is in the cards.
Back to the oil leak. Asking IDK for sure if you replaced a vacuum module to trans they could leak there out of a swollen vacuum hose that fell off is ATF takes loss of a bit to see it low for sure at first. Just a thought on just that isn't the grinding at all,


T



My79blazer
New User

Dec 7, 2019, 9:06 PM

Post #4 of 8 (624 views)
Re: 1979 Chevy Blazer having weird drivetrain issues! Sign In

Yeah, there are a lot of things i need to do but i am disabled so i have the time, only really need to drive less than 5 miles a day max on average so i can deal with some things until i can check them off my list as annoying as they are. Main thing is just being able to make trips to the store and take the kids to occasional doctor appointments.

The oil leak is annoying for sure but only having to put a quart in about every week and a half to two weeks is manageable until I have the time and money to do an overhaul on the gaskets. Getting it rolling down the road safe enough to have they boys in it is priority number one to me. Not sure how long it sat before i bought it but she sat for about 8 months with very minimal action after i bought it.

The thing that weirds me out the most is that it doesn't seem to kick itself "out of gear" like it usually does when a transfer case is going out. And the tranny showed no signs of late/hard shifts, whinning noise (other than the recent occasional quick grind sound)_ wasn't losing fluid, fluid looked great with no particulates so I don't think it's the problem either. I simply replaced the modulator because the vacuum system was a mess when i bought it and wanted to change it then, having shifting issues now just seemed like the right time.
The more I think on it the more it confuses me. So, I am slowly checking things off my list trying to start with the cheaper things that were already on my list or are probably a possibility but likely couldn't hurt to do anyway.

I like doing the work, gives me purpose since I got disabled, plus it's good experience for my sons to learn this stuff. Not many 13 year olds know how to replace lifters and rods in a few hours anymore. But I agree, I bought it as a tinker toy not a daily driver but it's what I got for now and I can buy a lot of parts for it to equal the same price as a monthly car payment or buying a cheap used car that could need a lot of work too. A buddy of mine has a 99 s10 in really good working order he is debating just signing over to me but someone is currently using it until they find a new car so this might not be a daily driver for long anyway.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 8, 2019, 4:00 AM

Post #5 of 8 (604 views)
Re: 1979 Chevy Blazer having weird drivetrain issues! Sign In

Top line you said it was a "Toy" for you and will be. Again, I just don't think even OMG just 5 miles a day it's ready for even that without lots of time and unknown costs.
Speak for myself too the "fixer upper(s)" need another vehicle to go chase down parts if even part way thru anything need something or it's disabled.


Hey, That '99 could be the right something if able to use every day now sounds off to a better start.


Side note is watch out for just 5 mile total drives ALL the time. Any vehicle that's just not fully warmed up they don't like that, engines, brakes, exhaust and almost all fuel may be the problem should be kept full but used up - a conflict there with that use. Me too on that - no mile use still use it up. Dang fuel stabilizers cost more than the fuel only helps get more time,


T



gsferraro
Enthusiast

Dec 8, 2019, 10:41 AM

Post #6 of 8 (580 views)
Re: 1979 Chevy Blazer having weird drivetrain issues! Sign In

Hello,
Question, Do you hear the grinding noise in 2wd and not 4wd? Gary


My79blazer
New User

Dec 8, 2019, 7:46 PM

Post #7 of 8 (566 views)
Re: 1979 Chevy Blazer having weird drivetrain issues! Sign In

Yes. It does it in both.


gsferraro
Enthusiast

Dec 10, 2019, 7:12 PM

Post #8 of 8 (526 views)
Re: 1979 Chevy Blazer having weird drivetrain issues! Sign In

Hows is the linkage for the T-case, move freely? Gary, sorry for late reply, shop is packed






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