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1976 Chevrolet pickup with Th350


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TravisH
User

Jul 10, 2019, 10:58 AM

Post #1 of 22 (451 views)
  post locked   1976 Chevrolet pickup with Th350  

On my Chevy truck equipped with TH350 transmission I have started to notice a clicking noise only when the truck is moving. I finally isolated the noise where the speedometer cable connects to the transmission disconnected the cable with the truck in neutral it still makes the sound. I also notice the speedometer calibration gear box moves side to side depending on direction I would rotate the driveshaft when it moved is when I would hear the click and it is loose I mean you can make it wobble with little effort as well even with hold down clamp tightened. Not sure if it’s supposed to be like as described or not.

Thankyou


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 10, 2019, 3:51 PM

Post #2 of 22 (435 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Site trans specialist should be by I do recall those add on things for this trans if and seemed only if you rebuild one that didn't match the rear end's gear ratio had a few choices used those not OE that I knew of??
Trans was so, so popular goes back many more model years just FYI the extension housings were different for different vehicles. Other was vacuum to a diaphragm would have constant vacuum when available (passenger's side??) could leak oil to intakes and put out a fog. Olds versions didn't use trans for speedo cable wasted a day putting one in another and OOOPS not speedo spot to hook up!
Noise? Best I know it just a shaft there nothing moving if driveshaft isn't. Best I can do overhauled like one ATF would lean if shaft was out. Let the guy check in why the noise so far I don't think it can mechanically but maybe fluid rushing somehow could make that thing move??
Do note if it works properly, fluid level and color of it should just be posted anyway I'll just add if it's full of bubbles on stick too,


T


TravisH
User

Jul 10, 2019, 4:45 PM

Post #3 of 22 (423 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

I had to look up on the internet to find the proper name for this part being speedometer calibration gear box. Sounds like this particular part is not factory then. Everything seems to work as it should the transmission Sh!ts good as it should it has new ATF it just started doing this clicking when driving and only in drive tried it in reverse but didn’t hear it in that gear. The speedometer also seem to be working properly. Thankyou Tom for your help I’ll keep tinkering with it till it’s figured out.

This just came to mind after re reading you response to my question.
Couldn’t the gears be changed I’ve seen speedometer gear assortments for sale wouldn’t that accomplish the same thing this ad on part does?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 10, 2019, 5:41 PM

Post #4 of 22 (417 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

THE site specialist's username is "gsferraro" will be by when he can. Too late, didn't want him to have to read thru this part but could expound on it. Only reason I knew of this thing was a family owned (from new) '74 Suburban, 350- 4V, TH350 very similar to the truck/trucks. So dang many miles on the thing trans just got old a couple times.


No, I didn't redo it had a guy who did that wholesale in a day that's all he did. Came back one of the times speedometer was reading wrong. I think while I waited left it was right saw that thing on the side dangling and speedo cable connected to a lower end of it. Bear with me it was freaking ages ago.


I was already used to some other vehicle makes you adjusted bands in automatics periodically this one you couldn't meant it wore out beyond a new hair-do if you will used a good "core" used to rebuild instead.


The only point is there was a way to "calibrate" it totally a gear thing no electrical anything on it. If that thing wobbled IDK was a time I'd probably things like hang under a vehicle while moving to watch stuff?


IDK if one was adjustable or just picked one to match? Hey - this still exists for you noted these rusted out as fast as anything ever made so the wild high miles on the one I knew best didn't get too old do recall a center bearing would allow driveshaft to whip and rattle but isn't moving if still as you said this was when observed.


Let it be till Gary is his name comes by with ideas for you. It couldn't be a specialty for me worked alone then heavy stuff was a problem just any help some stuff just can't do 100% alone,


T


TravisH
User

Jul 10, 2019, 7:06 PM

Post #5 of 22 (413 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

I gotcha now Tom I wasn’t understanding you, when you mentioned gsferraro thought you were talking about a YouTube site on the subject we’ve been discussing.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jul 11, 2019, 12:31 AM

Post #6 of 22 (400 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Travis: Sorry for any confusion on my part and or typos the mess up the intended response. gsferraro is the user name of the specialist in about all things transmission. The site is and has been all volunteer only is NOT bound to any other branded medial like YouTube but it is used by users to show how things of all sorts work or what they look like and noises.
There's no proof anything you see is actually correct for any of it for your specific issue This site has no motive to sell anything to you or pushed by any other concern that I know of.
Back to the issue. My fault should have just let you post alone till he came by. TMK probably doesn't have as much time as some others comes by when he can and follows up on what the issue is.
This thread is blown in a way being so long now (my fault - sorry) for not stopping that just don't want days to go by without a response at all. It's probably best now to start over with your first post and one of us can just lock this one there is info in it. Said I knew of such things and TMK those were NOT adjustable calibration rather match speed of output shaft of a transmission to ratio of a differential still matters if you've altered tire size in the era around 1976 almost all speedometers were close but not certified as perfectly accurate. Close is useful, way off is not so that was a way.
It's not accuracy rather motion and noise of this thing so why for just that is unknown to me personally. It's probably quite old and I think just moving gears inside to convert output shaft gear to what dash speed and odometer were set for best I know.
They didn't make noise but anything with moving parts could. That's what you/we need to know what could cause it and what to do about it IMO if noisy the next thing is it will probably quit working.


That will be the end all important part to know what you can do about that now not things used in '76 may not be serviceable now and IDK if a selection of new things that do that is easily available?
Let this sit one more day, remind me if nothing and perhaps start it over just top post again and leave it alone? Tom



TravisH
User

Jul 11, 2019, 6:27 AM

Post #7 of 22 (391 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Tom, no need for apologies I now understand what you were trying to say.


gsferraro
Enthusiast

Jul 16, 2019, 4:25 PM

Post #8 of 22 (363 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Hello,
Was out of town, does the noise change as engine speed increases. Is that housing leaking? Gary


TravisH
User

Jul 16, 2019, 8:45 PM

Post #9 of 22 (350 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Howdy, thankyou for getting back with me. No the housing isn’t leaking And the clicking does seem to increase with speed. I have had it up on jack stands trying to isolate the sound and noticed every half turn of the drive shaft it would make that clicking sound and it is alway the same two position of the drive shaft and never changes when rotating the driveshaft. I hope I’m making sense describing what is going on here.


gsferraro
Enthusiast

Jul 17, 2019, 4:20 PM

Post #10 of 22 (334 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Ok, do you actually hear this while driving?. The governor is right back there as well, as the shaft turns the weights on the governor open and close


TravisH
User

Jul 17, 2019, 5:44 PM

Post #11 of 22 (328 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Yes I do hear the clicking when driving that’s how I first noticed it. Sorry for any confusion when I drive the truck past where the sound can bounce back I hear it even better.


gsferraro
Enthusiast

Jul 18, 2019, 5:00 PM

Post #12 of 22 (303 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Hello,
I honestly not long ago I had a car with a similar problem, the complaint was similar to yours. The fix was changing out the park pawl and spring. Do you hear this more above like 30 mph?


Double J
Veteran / Moderator
Double J profile image

Jul 18, 2019, 8:08 PM

Post #13 of 22 (288 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Didn't see it mentioned so I thought I'd throw this out there

Did you check to see if maybe you just have a worn Universal Joint(s)?


TravisH
User

Jul 18, 2019, 8:52 PM

Post #14 of 22 (282 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

I can’t say if going 35mph or faster that I hear it more when I hear it the best is when I drive down rural road where I live driving say 20mph just hear that clicking. As we had talked earlier I can replicate the clicking sound just at slower rate with transmission in neutral up on jack stands rotating a wheel or the driveshaft it sure sounds like it’s coming from the transmission. I’ve heard of parking pawls going bad and could be the culprit everything wears are these parts regularly available for TH350 if this turns out to be this case. Appreciate the help sounds like it’s going the be a process of limitation any more ideas let me know.

Travis


TravisH
User

Jul 18, 2019, 8:59 PM

Post #15 of 22 (279 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Thankyou for your thoughts once I’m able to get back to working on it I’ll be able to narrow down the problem.


TravisH
User

Jul 20, 2019, 1:03 PM

Post #16 of 22 (256 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Well, I think I’ve narrowed down the clicking sound and believe you were right about the governor. Got back under the pick-up today with a stethoscope moving it around where I thought the noise was coming from manually rotating the transmission finally isolating by put it at the governor cover and that’s when I heard the clicking clearly.
My next question about replacing the governor I’ve been looking on the internet and they are listed are all th350 governors the same or do trucks use heavier duty governor than cars or are they the same?

Thankyou:
Travis


gsferraro
Enthusiast

Jul 20, 2019, 5:46 PM

Post #17 of 22 (243 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Hello,
The govenors are the same but it's the spring tension that makes the difference. If you get another one, may do the same thing, just weights are moving as the governor rotates. Gary


TravisH
User

Jul 20, 2019, 9:08 PM

Post #18 of 22 (233 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

 So this clicking in the governor is due to a broken or missing spring. I’ve seen governor calibration kits with different springs and tensions. There’s also rebuild kits plus reconditioned ones as well which direction would be the best path to take.

Thankyou;
Travis


gsferraro
Enthusiast

Jul 21, 2019, 6:15 AM

Post #19 of 22 (224 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

The weights will move to a certain position before the springs return them, many different spring tensions, have you driven the car to see how it works?


TravisH
User

Jul 21, 2019, 7:13 AM

Post #20 of 22 (212 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

I haven’t driven the vehicle since I figured out the clicking was coming from the transmission. I was just asking your opinion on the best route replacing it or rebuilding it myself and what type of governor would a stock transmission would have because I see these listed lock-up or non-lockup this for my own personal information. Thankyou for your help Gary.


TravisH
User

Aug 5, 2019, 1:11 PM

Post #21 of 22 (165 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Hi Garry:

I wanted to let you know that I got my problem with my TH350 you were helping me with is fixed. Installed a remand governor in it and test drove it and no clacking sound when the truck was moving. Appreciate all of your advice you gave me pointing out were to look and what to possibly look for.

Thanks;
Travis


gsferraro
Enthusiast

Aug 5, 2019, 6:19 PM

Post #22 of 22 (150 views)
  post locked   Re: 1976 Chevrolet pickup with Th350  

Thanks for the feed back, glad it's fixed. Gary






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