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Username Post: 1990 Chevy G20 - Rough shifting into OD        (Topic#352397)
Ncalexopoulos 
Poster
Posts: 4
Ncalexopoulos
Loc: Florida
Reg: 08-08-18
08-08-18 01:36 PM - Post#2742363    

I can’t find anything anywhere about this. I have a 1990 5.7l G20 Van with about 157k miles, complete with a vice grip door handle. She actually runs pretty great for how old she is and how big of a hoot the previous owner was. Anyways, enough with the boring talk... When she shifts out of neutral or park, it’s a pretty hard shift... enough where the brakes barely hold it back from moving an inch in the direction of the gear. It pains me knowing that it’s just slamming into gear. Also, and this is the weird part, in the mornings when she’s cold, she won’t shift into OD (goes into drive fine). I either have to wait for a good 10-15 seconds or rev it a tiny tiny bit and she cluster-pops into gear. Throughout the day it’s fine. Also, when traveling about 50 she keeps shifting in and out of the actual overdrive gear and killing gas. I believe I have the THM350, after much research... and obviously she’s an automatic. The guy I bought it from doesn’t know much and just brushed it off as “oh, the transmission will probably need a rebuild soon” and I won’t accept that. What kinds of things should I check? Could it just be the linkage? Or is it a solenoid possibly? I’ve never adjusted anything like that before and the Haynes manual is not very visual, at all. Also, the other day... and it’s only happened this one time, when my girlfriend shifted it into drive it stalled... she tried it again and it stalled... so I had her get out and I tried it and it worked fine but almost died. It hasn’t been back to that since *knocks on wood* could you guys help me out? If not, and if you can... do any of you guys have a parts compatibility list? Like for the ac pump and what not? I’m very tight on money, and thank you

Blue Willie
1990 Chevy G20 5.7l Conversion Van
Yes, I live in it with my girlfriend
  • Quote:
Never pull out



 
454cid 
Valued Contributor
Posts: 2921

Age: 45
Loc: West Michigan
Reg: 02-18-12
08-08-18 03:36 PM - Post#2742373    
    In response to Ncalexopoulos

  • Ncalexopoulos Said:
..I believe I have the THM350.



The TH350 doesn't have over drive. It's probably a 700R4


99 K3500 RCLB


 
Ncalexopoulos 
Poster
Posts: 4
Ncalexopoulos
Loc: Florida
Reg: 08-08-18
08-09-18 10:52 AM - Post#2742484    
    In response to 454cid

Ah, ok, thank you for that! The guy I bought it from didn’t even know

Blue Willie
1990 Chevy G20 5.7l Conversion Van
Yes, I live in it with my girlfriend
  • Quote:
Never pull out



 
raycow 
Honored Member
Posts: 27675
raycow
Loc: San Francisco, CA
Reg: 11-26-02
08-10-18 10:56 AM - Post#2742608    
    In response to Ncalexopoulos

The fastest way to tell would be to look at the shift quadrant. A TH700 will have an "O" or "OD" position in addition to "D". A TH350 will just have the "D".

Ray

Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.


 
Ncalexopoulos 
Poster
Posts: 4
Ncalexopoulos
Loc: Florida
Reg: 08-08-18
08-11-18 12:37 PM - Post#2742732    
    In response to raycow

Yup, do you maybe know why it slams into gear? Is it possibly a solenoid or just an adjustment?

Blue Willie
1990 Chevy G20 5.7l Conversion Van
Yes, I live in it with my girlfriend
  • Quote:
Never pull out



 
stumppuller 
"7th Year" Gold Supporting Member
Posts: 824
stumppuller
Loc: Canada
Reg: 11-01-04
08-11-18 09:21 PM - Post#2742784    
    In response to Ncalexopoulos

Assuming you have the 700-R4, it may simply be the transmission's TV cable is adjusted too tight.

Before you adjust it, just be aware that it is not a kickdown cable. Yes, it does affect the kickdown timing, but more importantly it sets the transmission's internal line pressure. Set it to low and the 700-R4 will die very quickly.

There is lot of discussion in the archives about adjusting it. Personally, I adjust it by how the truck feels/shifts.

- Hammer/very late shifts it's too tight.

- Soft/early shifts with late or no forced kickdown, too loose (and very bad).

- I set it for a good crisp shift at low to part throttle.


With reference to the attached picture,

Red = linkage at TBI
Purple = Depress center metal tab to adjust
Green = Toward TBI for softer shift. Away from TBI for firmer shift.



Attachment: TV_Cable_components.jpg (36.95 KB) 1 View(s)




-91 Sierra C2500, now K2500
-81 Chev K20


 
Ncalexopoulos 
Poster
Posts: 4
Ncalexopoulos
Loc: Florida
Reg: 08-08-18
08-14-18 07:59 AM - Post#2743032    
    In response to stumppuller

Dude, you’re the man, thank you! I knew it was probably something simple to fix. I’ll come back on and let y’all know how that goes today or tomorrow

Blue Willie
1990 Chevy G20 5.7l Conversion Van
Yes, I live in it with my girlfriend
  • Quote:
Never pull out



 
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