4x4 TH350 Slow into gear - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**hotrodmtodd** · 01-09-2011, 02:40 PM

Lets try this in the main forum. Posted in the Blazer section and didnt get a single response. Have a TH350 in my 72 Blazer that has been sitting for 2 years. It worked great up until I parked it. It is sporadically slow going into both drive and reverse. It will work perfect one time, the next time, I have to rev it up a little to get it to engage. Doesnt matter about cold, hot or otherwise. It is just random. Replaced the fluid, filter and gasket, some aluminum and steel in the pan. Added some Seafoam trans tune to try and flush it out a little. Could this be a modulator issue, or is this thing trying to tell me its toast? If it is, I am going to do a 3 or 4 speed manual swap, most likely since I have both set ups. Just curious if you guys have any opinions on this tranny, or which of the manual swaps would be the least time consuming. Thanks guys.

fattyarbuckle · 01-09-2011, 03:26 PM

Don't think a modulator will cause that problem.

A valve in the valve body could be sticking or a lip seal no sealing. You might try re-building or taking the valve body off and cleaning all the components...be sure and have a manual when you do.

turp mcspray · 01-10-2011, 12:19 PM

I had one once that was slow to engage. If I snapped the throttle, it helped. I tried a new modulator, and it cured the problem. They are cheep enough, that I would try one, before opening up the trans.

**hotrodmtodd** · 01-10-2011, 08:03 PM

Yes, sounds like the same problem you had. Bought a modulator today at work. Will give that a try first. Will let you guys know what happens. Thanks for the responses.

swamp rat · 01-11-2011, 11:42 PM

Updates?

**hotrodmtodd** · 01-12-2011, 08:46 PM

Installed the new modulator and it is pretty much acting the exact same way. Any other ideas? I will consider trying anything at this point. I am going to have to make some tough decisions here soon. Let me know what you think.

SIDS65 · 01-12-2011, 10:33 PM

If I remember right the 1st gear and reverse clutches are in the same pack together and if it is slipping or not going into gear very quick it could be a bad set of clutches or the lip seal could be dried out and not sealing. A governor sticking wont let it shift and a broken accumulator spring will cause a hard engagement going into gear. Most generally if it isnt engaging when you put it in gear and you hit the throttle to get it to engage than something is allowing the fluid to bypass and not apply psi to the clutches. I havent been around building transmissions in years and probably forgot more than I knew about them but I would say you should look at a swap or a rebuild. Sitting 2 years allows all the fluid to drain down and the seals dry out. Good luck.

fattyarbuckle · 01-13-2011, 12:31 AM

Quote:

Originally Posted by hotrodmtodd

Installed the new modulator and it is pretty much acting the exact same way. .

really?

72-c20 · 01-13-2011, 10:04 AM

be sure to check all vac hoses. mine was acting funny and it was because of a bad hose...

01-09-2011, 02:40 PM	#1
hotrodmtodd 'Burban Legend Join Date: Apr 2005 Location: Mingo Junction OH Posts: 918	4x4 TH350 Slow into gear Lets try this in the main forum. Posted in the Blazer section and didnt get a single response. Have a TH350 in my 72 Blazer that has been sitting for 2 years. It worked great up until I parked it. It is sporadically slow going into both drive and reverse. It will work perfect one time, the next time, I have to rev it up a little to get it to engage. Doesnt matter about cold, hot or otherwise. It is just random. Replaced the fluid, filter and gasket, some aluminum and steel in the pan. Added some Seafoam trans tune to try and flush it out a little. Could this be a modulator issue, or is this thing trying to tell me its toast? If it is, I am going to do a 3 or 4 speed manual swap, most likely since I have both set ups. Just curious if you guys have any opinions on this tranny, or which of the manual swaps would be the least time consuming. Thanks guys. __________________ '67 Chevy Iron City Beer Truck (9ft step) '67 Chevy Panel Truck 467 '68 Short Fleet 305v6 '68 McLaren Ramp Truck '68/'68/'70/'71 Burbs 292/366/402/454 '69 C-30 dump '71 C-50 dump and church bus '71 4x4 454 '72 Blazer (w/pop-up camper) $15 x-hooks '66 Chevy II 194/Weber '68 El Camino" 305v6 '69 Skylark 455 Buick '70 Chevelle 427 '71 Cutlass W-31 '71 GTO 400 2x2 "The 51" Chopped '51 Chevy (409) my first car OK Toad, we'll take 'em all... John Milner

01-09-2011, 03:26 PM	#2
fattyarbuckle Registered User Join Date: Nov 2010 Location: St. Louis Mo. Posts: 282	Re: 4x4 TH350 Slow into gear Don't think a modulator will cause that problem. A valve in the valve body could be sticking or a lip seal no sealing. You might try re-building or taking the valve body off and cleaning all the components...be sure and have a manual when you do.

01-10-2011, 12:19 PM	#3
turp mcspray Registered User Join Date: May 2007 Location: Rapid City South Dakota Posts: 2,359	Re: 4x4 TH350 Slow into gear I had one once that was slow to engage. If I snapped the throttle, it helped. I tried a new modulator, and it cured the problem. They are cheep enough, that I would try one, before opening up the trans. __________________ Turp Mcspray New life for an old 2wd, farm blazer http://67-72chevytrucks.com/vboard/s...d.php?t=505987 My Blazer build http://67-72chevytrucks.com/vboard/s...d.php?t=342299

01-10-2011, 08:03 PM	#4
hotrodmtodd 'Burban Legend Join Date: Apr 2005 Location: Mingo Junction OH Posts: 918	Re: 4x4 TH350 Slow into gear Yes, sounds like the same problem you had. Bought a modulator today at work. Will give that a try first. Will let you guys know what happens. Thanks for the responses. __________________ '67 Chevy Iron City Beer Truck (9ft step) '67 Chevy Panel Truck 467 '68 Short Fleet 305v6 '68 McLaren Ramp Truck '68/'68/'70/'71 Burbs 292/366/402/454 '69 C-30 dump '71 C-50 dump and church bus '71 4x4 454 '72 Blazer (w/pop-up camper) $15 x-hooks '66 Chevy II 194/Weber '68 El Camino" 305v6 '69 Skylark 455 Buick '70 Chevelle 427 '71 Cutlass W-31 '71 GTO 400 2x2 "The 51" Chopped '51 Chevy (409) my first car OK Toad, we'll take 'em all... John Milner

01-11-2011, 11:42 PM	#5
swamp rat Registered User Join Date: Oct 2007 Location: Spanaway Posts: 8,451	Re: 4x4 TH350 Slow into gear Updates? __________________ Mike. Swamp Rat build thread : http://67-72chevytrucks.com/vboard/s...d.php?t=595019 72 3/4T 4X4 4" BDS Lift 33" BFG's

01-12-2011, 08:46 PM	#6
hotrodmtodd 'Burban Legend Join Date: Apr 2005 Location: Mingo Junction OH Posts: 918	Re: 4x4 TH350 Slow into gear Installed the new modulator and it is pretty much acting the exact same way. Any other ideas? I will consider trying anything at this point. I am going to have to make some tough decisions here soon. Let me know what you think. __________________ '67 Chevy Iron City Beer Truck (9ft step) '67 Chevy Panel Truck 467 '68 Short Fleet 305v6 '68 McLaren Ramp Truck '68/'68/'70/'71 Burbs 292/366/402/454 '69 C-30 dump '71 C-50 dump and church bus '71 4x4 454 '72 Blazer (w/pop-up camper) $15 x-hooks '66 Chevy II 194/Weber '68 El Camino" 305v6 '69 Skylark 455 Buick '70 Chevelle 427 '71 Cutlass W-31 '71 GTO 400 2x2 "The 51" Chopped '51 Chevy (409) my first car OK Toad, we'll take 'em all... John Milner

01-12-2011, 10:33 PM	#7
SIDS65 Registered User Join Date: Jan 2007 Location: Kincaid IL Posts: 26	Re: 4x4 TH350 Slow into gear If I remember right the 1st gear and reverse clutches are in the same pack together and if it is slipping or not going into gear very quick it could be a bad set of clutches or the lip seal could be dried out and not sealing. A governor sticking wont let it shift and a broken accumulator spring will cause a hard engagement going into gear. Most generally if it isnt engaging when you put it in gear and you hit the throttle to get it to engage than something is allowing the fluid to bypass and not apply psi to the clutches. I havent been around building transmissions in years and probably forgot more than I knew about them but I would say you should look at a swap or a rebuild. Sitting 2 years allows all the fluid to drain down and the seals dry out. Good luck.

01-13-2011, 10:04 AM	#9
72-c20 Packrat Join Date: May 2008 Location: Central Iowa Posts: 459	Re: 4x4 TH350 Slow into gear be sure to check all vac hoses. mine was acting funny and it was because of a bad hose... __________________ gone: --'07 Tahoe LTZ 4WD --'68 Firebird 400 Convertible gone: --'72 Chevy K20



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