How to identify auto tranny type? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

berghandler · 03-07-2018, 02:27 PM

I'm trying to make sure what type of automatic transmission that's on my grandsons 1972
C/20 Delux. It has a 350 engine but not sure if it's a t350 or t400. It needs to be replaced and I want to make sure we get it right when looking for another. Can any one out there give me some sure indicators on what to look for to tell if it's a t350 or t400 on the truck now. It is the original tranny.
Thanks

demian5 · 03-07-2018, 02:34 PM

Here you go.

700r-4 also applies to the 4L60 and 4L60-E

**HO455** · 03-07-2018, 02:37 PM

Those are transmission oil pan shapes. Compare them to yours to decide which one you have.

**LockDoc** · 03-07-2018, 02:37 PM

-
Here is another one.

LockDoc

harpo231 · 03-07-2018, 02:38 PM

http://67-72chevytrucks.com/vboard/a...1&d=1520447840

Hope this helps ...

geezer#99 · 03-07-2018, 03:19 PM

When you look for a replacement, make sure you get one with the correct tail shaft housing length.

**Steeveedee** · 03-07-2018, 04:05 PM

Quote:

Originally Posted by geezer#99

When you look for a replacement, make sure you get one with the correct tail shaft housing length.

Yup. It'd be a bummer to get one with the wrong length tail shaft.

OP- see if you can post a picture. It can save a lot of pain. What are the symptoms that you deem make replacement necessary?

berghandler · 03-08-2018, 11:53 AM

It slips bad in first gear when starting out, unless you baby it when you take off.

MARKDTN · 03-08-2018, 01:13 PM

I would have yours built instead of getting another. You know it fits, you know a little about it. It has to come out anyway, just build it. But you might service it and it may go a bit longer. Could be the filter is clogged. I would at least pull the pan and take a look.

Another tell-apart is a TH350 has the vacuum modulator at the rear of the trans while a TH400 has the modulator on the right side towards the front.

cleszkie · 03-08-2018, 02:31 PM

Quote:

Originally Posted by berghandler

it is the original tranny.
Thanks

Check the SPID.

68Gold/white · 03-08-2018, 02:36 PM

Another...late transmissions do not have vacuum modulators, oldies do...

Powerglide, modulator is behind pan on drivers side

TH350, modulator is behind pan on pass side.

TH400 modulator is forward of pan on pass aide, usually visible from under hood...

**3757chevy** · 03-09-2018, 01:51 AM

th350 has detent cable on drivers side of carb. th400 has electric kickdown switch on throttle pedal inside cab

03-07-2018, 02:27 PM	#1
berghandler Registered User Join Date: Feb 2004 Location: FOnd du Lac, WI. Posts: 32	How to identify auto tranny type? I'm trying to make sure what type of automatic transmission that's on my grandsons 1972 C/20 Delux. It has a 350 engine but not sure if it's a t350 or t400. It needs to be replaced and I want to make sure we get it right when looking for another. Can any one out there give me some sure indicators on what to look for to tell if it's a t350 or t400 on the truck now. It is the original tranny. Thanks

03-07-2018, 02:34 PM	#2
demian5 Registered User Join Date: Aug 2016 Location: Lake Forest, CA Posts: 2,177	Re: How to identify auto tranny type? Here you go. 700r-4 also applies to the 4L60 and 4L60-E Attached Images __________________ "Work hard, use your vacation days." 1970 C15 GMC Long Bed 1986 C20 Scottsdale 1983 K2500 Sierra Classic Suburban 6.2 Instagram: C10sofOC

03-07-2018, 02:37 PM	#3
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 10,804	Re: How to identify auto tranny type? Those are transmission oil pan shapes. Compare them to yours to decide which one you have. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

03-07-2018, 02:37 PM	#4
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,331	Re: How to identify auto tranny type? - Here is another one. LockDoc Attached Images __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 -

03-07-2018, 02:38 PM	#5
harpo231 Registered User Join Date: Nov 2014 Location: Lincoln City DE Posts: 1,292	Re: How to identify auto tranny type? http://67-72chevytrucks.com/vboard/a...1&d=1520447840 Hope this helps ... Attached Images __________________ Stan 67 swb BLU MULE posted via flip-fone

03-07-2018, 03:19 PM	#6
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,514	Re: How to identify auto tranny type? When you look for a replacement, make sure you get one with the correct tail shaft housing length.

03-08-2018, 11:53 AM	#8
berghandler Registered User Join Date: Feb 2004 Location: FOnd du Lac, WI. Posts: 32	Re: How to identify auto tranny type? It slips bad in first gear when starting out, unless you baby it when you take off.

03-08-2018, 01:13 PM	#9
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,131	Re: How to identify auto tranny type? I would have yours built instead of getting another. You know it fits, you know a little about it. It has to come out anyway, just build it. But you might service it and it may go a bit longer. Could be the filter is clogged. I would at least pull the pan and take a look. Another tell-apart is a TH350 has the vacuum modulator at the rear of the trans while a TH400 has the modulator on the right side towards the front. __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project

03-08-2018, 02:36 PM	#11
68Gold/white Registered User Join Date: Sep 2011 Location: Ark City, Kansas Posts: 3,280	Re: How to identify auto tranny type? Another...late transmissions do not have vacuum modulators, oldies do... Powerglide, modulator is behind pan on drivers side TH350, modulator is behind pan on pass side. TH400 modulator is forward of pan on pass aide, usually visible from under hood...

03-09-2018, 01:51 AM	#12
3757chevy Senior Member Join Date: Mar 2016 Location: Near Canon City ,Colorado Posts: 3,852	Re: How to identify auto tranny type? th350 has detent cable on drivers side of carb. th400 has electric kickdown switch on throttle pedal inside cab __________________ '35 1/2 ton Pickup (bought 2020) '68 C10 Suburban (bought 2021) '72 K5 Blazer (bought 2013) '67 Stepside (bought 1997-sold 2021) '96 Bronco Eddie Bauer (inherited 2010) My 1st day here-'67 C10(sold)and '72 K5 Blazer http://67-72chevytrucks.com/vboard/s...d.php?t=702056 "Another Blue Chevy"(1935) http://67-72chevytrucks.com/vboard/s...d.php?t=799203 '68 Burb...https://67-72chevytrucks.com/vboard/...d.php?t=822994 MIKE



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