The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 05-04-2018, 02:17 PM   #1
Thatguywithaneye
Registered User
 
Thatguywithaneye's Avatar
 
Join Date: Oct 2017
Location: Kamloops BC, Canada
Posts: 20
What transmission do I have? 72 Sierra Grande

Trying to find a replacement tranny, but Iím having a hard time figuring out which one to search for. 72 GMC Sierra Grande with the 350 engine. Itís an automatic and it leaks like crazy! Probably 4 litres of atf fluid on the driveway. The option # on my sticker says M49-Turbo Hydra-Matic, but I know that could mean itís the TH350 or TH400. Where do I need to look to figure this out?

Thanks,
The new guy
Thatguywithaneye is offline   Reply With Quote
Old 05-04-2018, 02:46 PM   #2
sick472
Registered User
 
sick472's Avatar
 
Join Date: Jul 2015
Location: Sedalia Mo.
Posts: 652
Re: What transmission do I have? 72 Sierra Grande

The TH350 has a square or rectangular pan with a bit of one corner missing while the 400 has a funky shaped one. I can't really explain it's shape so look it up. Part of it kinda looks like the lower half of Texas. I believe the vacuum modulator on the 350 is on the right front while the 400 has it on the right rear. The 350 has a kickdown, cable, the 400 does not, it has an electrical swicth.
__________________
He who is without oil shall throw the first rod. Compressions 8.7:1
sick472 is offline   Reply With Quote
Old 05-04-2018, 03:37 PM   #3
Coley
Registered User
 
Coley's Avatar
 
Join Date: Oct 2011
Location: Victoria, B.C
Posts: 3,794
Re: What transmission do I have? 72 Sierra Grande

As Sick471 mentioned the TH350 has a 45 degree scallop out of the rear corner and it is largely square in shape otherwise.
The TH400 is clearly longer than it is wide and the TH400 has a 'bump' out on one side defeating the rectangular shape in the rear area....basically the TH400 looks a bit like a race car circuit with only a couple of square corners I think.

Coley
__________________
....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL
1966 Chevy 1/2 ton (Florida- Red/white)
1972 Chevy 1/2 ton (California- Blue/white)
2005 Chevy Silverado HD2500/Duramax
2000 Dodge Ram 1500
Coley is offline   Reply With Quote
Old 05-04-2018, 03:45 PM   #4
Thatguywithaneye
Registered User
 
Thatguywithaneye's Avatar
 
Join Date: Oct 2017
Location: Kamloops BC, Canada
Posts: 20
Re: What transmission do I have? 72 Sierra Grande

Quote:
Originally Posted by sick472 View Post
The TH350 has a square or rectangular pan with a bit of one corner missing while the 400 has a funky shaped one. I can't really explain it's shape so look it up. Part of it kinda looks like the lower half of Texas. I believe the vacuum modulator on the 350 is on the right front while the 400 has it on the right rear. The 350 has a kickdown, cable, the 400 does not, it has an electrical swicth.
Thanks! Iíve determined that itís the TH350. Square with the corner cut off is exactly what it looks like.

On another note have you ever seen an extreme leak from one of these?
Attached Images
 
Thatguywithaneye is offline   Reply With Quote
Old 05-04-2018, 04:50 PM   #5
Rich69shortfleet
Registered User
 
Join Date: May 2016
Location: Waverly, NE
Posts: 333
Re: What transmission do I have? 72 Sierra Grande

They ALL seem to leak from one place or another, but that one looks pretty slimy. If it is just generally tired and leaky why not have it rebuilt instead of buying a new one? Unless you want to upgrade to a more modern overdrive transmission or something. One thing to note, the truck TH350s are different than the car TH350s, the truck versions have one or two more clutch packs than the car versions.
Rich69shortfleet is offline   Reply With Quote
Old 05-07-2018, 12:04 AM   #6
Thatguywithaneye
Registered User
 
Thatguywithaneye's Avatar
 
Join Date: Oct 2017
Location: Kamloops BC, Canada
Posts: 20
Re: What transmission do I have? 72 Sierra Grande

Quote:
Originally Posted by Rich69shortfleet View Post
They ALL seem to leak from one place or another, but that one looks pretty slimy. If it is just generally tired and leaky why not have it rebuilt instead of buying a new one? Unless you want to upgrade to a more modern overdrive transmission or something. One thing to note, the truck TH350s are different than the car TH350s, the truck versions have one or two more clutch packs than the car versions.
The transmission was rebuilt twice by the previous owner (my grandpa) back in the 90's, but it never fixed it. He has tried everything from new seals and gaskets to a full blown rebuild and it fixes it for a few months and then the leak progressively gets worse. I have a feeling that the metal is warped where the engine meets, but that doesn't seem to be the only location. I will take it in to a transmission specialist and see what they say, but I don't want to fix it again. I found a brand new factory tranny for $1400.

Thank you for the information on the differences between the car and truck though, I will definitely use that.
Thatguywithaneye is offline   Reply With Quote
Old 05-07-2018, 11:30 AM   #7
demian5
Registered User
 
demian5's Avatar
 
Join Date: Aug 2016
Location: Lake Forest, CA
Posts: 2,175
Re: What transmission do I have? 72 Sierra Grande

Looks like the dipstick o-ring side leaking. Also the pans can get bent up and leak. I had to use 2 gaskets and "the right stuff" to seal up one once.
__________________
"Work hard, use your vacation days."
1970 C15 GMC Long Bed
1986 C20 Scottsdale
1983 K2500 Sierra Classic Suburban 6.2
Instagram: C10sofOC
demian5 is offline   Reply With Quote
Old 05-07-2018, 03:14 PM   #8
MARKDTN
Registered User
 
Join Date: Jan 2011
Location: Chattanooga, TN
Posts: 1,781
Re: What transmission do I have? 72 Sierra Grande

A good shop should be able to fix that. The TH350 is a pretty simple transmission.
__________________
'83 K20-TPI
'79 C10-ex-diesel(SOLD)
'01 Tahoe
'07 Tahoe-DD
MARKDTN is offline   Reply With Quote
Old 05-07-2018, 04:51 PM   #9
BCOWANWHEELS
Senior Member
 
Join Date: Nov 2006
Location: KINGSPORT,TN.
Posts: 3,006
Re: What transmission do I have? 72 Sierra Grande

yep, pull it and take to trans shop
__________________
I BELIEVE IN JOHN 3:16
BCOWANWHEELS is offline   Reply With Quote
Reply

Bookmarks

Tags
350, automatic, m49, sierra grande, transmission

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 04:08 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Copyright 1997-2020 67-72chevytrucks.com