Thought I had a turbo 400... (375?) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SRH916 · 03-19-2008, 07:56 AM

So I was under the truck, just about 5 minutes ago

and on the "tail something" of the transmission i read 375 th* (some other letter) So now I think I have a 375. What was the whole thing about them again? a turbo 400 in a housing?

Bishops Trucks · 03-19-2008, 08:19 AM

There is no such thing as a "375 TH". Does your trans have a cable kickdown ("350 TH") from the carb to the trans or does it have an electric kickdown switch ("400 TH") from the carb to the trans.(2 wires go to a switch mounted in the trans). I have no clue what the "375" means.

SRH916 · 03-19-2008, 08:31 AM

so apparently the thm-375 is a "light duty" thm-400. it just has a 350 driveshaft yoke. hmm
wonder what gears are in it, anyone know?

lawson86 · 03-19-2008, 09:08 AM

THM375B - This trans is identical to the THM350, but is considered a heavier duty transmission. Gear ratios on these units were 2.52 1st gear, 1.52 2nd gear, 1.00 3rd gear.

THM375 - This transmission is a derivative of the THM400 sharing the external appearance of the 400. It'll be marked 375-THM on the bottom of the tailshaft housing. It's a light duty version of the THM400, has ABSOLUTELY NO RELATION to the THM375B, and was found in 1972 to 1976 full-size cars. The Turbo 375 was modified to accept the Turbo 350 driveshaft yoke.
Gear ratios on these units were 2.48 1st gear, 1.48 2nd gear, 1.00 3rd gear.

Bishops Trucks · 03-19-2008, 09:49 AM

I stand corrected!

Malo83 · 03-19-2008, 11:01 AM

Learn something new everyday

lawson86 · 03-19-2008, 11:25 AM

My tranny guy gave me this lesson few years ago when I took what I thought was a THM400 to rebuild that was my day to learn

Curly86 · 03-19-2008, 02:21 PM

I just learned something new I didn't know the made a 375 either

streetstar · 03-23-2008, 09:19 AM

The 375 was the "long tail 400" amongst my bench racing circles of yesteryear.

I've actually never seen one in person, but then again i've never seen a reasonable woman either, although i know they exist somewhere

MylilBowTie · 03-23-2008, 07:28 PM

Do you have a pic of the id tag on the passenger side of the trans?

SRH916 · 03-24-2008, 03:54 AM

ill try to get one soon, but i forsure saw the THM 375 on the driveshaft yoke

03-19-2008, 07:56 AM	#1
SRH916 1975 C-10 Silverado LWB Join Date: Nov 2007 Location: Sacramento, CA Posts: 326	Thought I had a turbo 400... (375?) So I was under the truck, just about 5 minutes ago and on the "tail something" of the transmission i read 375 th* (some other letter) So now I think I have a 375. What was the whole thing about them again? a turbo 400 in a housing? __________________ 1975 LWB C-10 Silverado - Stock - "BIG 10" - 4 Bolt 350 "Brand new" 1200mi - THM-375 "Brand new w/trans cooler" 5000mi 1995 Ford Lightning - Bone Stock - 351W - Vortech??

03-19-2008, 08:19 AM	#2
Bishops Trucks KEEP ON TRUCKIN' Join Date: Jun 2005 Location: Sterling, Va. Posts: 5,731	Re: Thought I had a turbo 400... (375?) There is no such thing as a "375 TH". Does your trans have a cable kickdown ("350 TH") from the carb to the trans or does it have an electric kickdown switch ("400 TH") from the carb to the trans.(2 wires go to a switch mounted in the trans). I have no clue what the "375" means. __________________ JIM '97 GMC Sierra K1500 '95 Chevy Silverado C1500 '71 Cheyenne Z71 / LT1 & 4-Speed SWB K/10 Father/Son Project http://www.youtube.com/watch?v=4l689JKXPnA http://67-72chevytrucks.com/vboard/payments.php "LIVIN' FREE FOREVER"

03-19-2008, 08:31 AM	#3
SRH916 1975 C-10 Silverado LWB Join Date: Nov 2007 Location: Sacramento, CA Posts: 326	Re: Thought I had a turbo 400... (375?) so apparently the thm-375 is a "light duty" thm-400. it just has a 350 driveshaft yoke. hmm wonder what gears are in it, anyone know? __________________ 1975 LWB C-10 Silverado - Stock - "BIG 10" - 4 Bolt 350 "Brand new" 1200mi - THM-375 "Brand new w/trans cooler" 5000mi 1995 Ford Lightning - Bone Stock - 351W - Vortech??

03-19-2008, 09:08 AM	#4
lawson86 Registered User Join Date: Nov 2007 Location: Inman,SC Posts: 93	Re: Thought I had a turbo 400... (375?) THM375B - This trans is identical to the THM350, but is considered a heavier duty transmission. Gear ratios on these units were 2.52 1st gear, 1.52 2nd gear, 1.00 3rd gear. THM375 - This transmission is a derivative of the THM400 sharing the external appearance of the 400. It'll be marked 375-THM on the bottom of the tailshaft housing. It's a light duty version of the THM400, has ABSOLUTELY NO RELATION to the THM375B, and was found in 1972 to 1976 full-size cars. The Turbo 375 was modified to accept the Turbo 350 driveshaft yoke. Gear ratios on these units were 2.48 1st gear, 1.48 2nd gear, 1.00 3rd gear. Last edited by lawson86; 03-19-2008 at 10:17 AM.

03-19-2008, 09:49 AM	#5
Bishops Trucks KEEP ON TRUCKIN' Join Date: Jun 2005 Location: Sterling, Va. Posts: 5,731	Re: Thought I had a turbo 400... (375?) I stand corrected! __________________ JIM '97 GMC Sierra K1500 '95 Chevy Silverado C1500 '71 Cheyenne Z71 / LT1 & 4-Speed SWB K/10 Father/Son Project http://www.youtube.com/watch?v=4l689JKXPnA http://67-72chevytrucks.com/vboard/payments.php "LIVIN' FREE FOREVER"

03-19-2008, 11:01 AM	#6
Malo83 Cruzzzn' Vet Join Date: Jan 2005 Location: Porterville,Ca. Posts: 1,918	Re: Thought I had a turbo 400... (375?) Learn something new everyday

03-19-2008, 11:25 AM	#7
lawson86 Registered User Join Date: Nov 2007 Location: Inman,SC Posts: 93	Re: Thought I had a turbo 400... (375?) My tranny guy gave me this lesson few years ago when I took what I thought was a THM400 to rebuild that was my day to learn

03-19-2008, 02:21 PM	#8
Curly86 You want it there when??? Join Date: Oct 2006 Location: Lewisburg Ky Posts: 393	Re: Thought I had a turbo 400... (375?) I just learned something new I didn't know the made a 375 either __________________ 1986 Silverado Flatbed 400 SB with 350 turbo 1997 Ford Explorer with 302 mydrive to work ride 1978 Gmc Midas RV 21ft with 46,000 actual miles 2003 Chevy Avalanche 5.3 327 and Tweety Bird Yellow Big Sandy Survivor 09 Trucks in the Blue Grass Survivor 09 TNCTC Streetcruzin

03-23-2008, 09:19 AM	#9
streetstar Registered User Join Date: May 2007 Location: Moore, Oklahoma Posts: 2,396	Re: Thought I had a turbo 400... (375?) The 375 was the "long tail 400" amongst my bench racing circles of yesteryear. I've actually never seen one in person, but then again i've never seen a reasonable woman either, although i know they exist somewhere __________________ Are you retired too? Nonsense! I'm in my prime

03-23-2008, 07:28 PM	#10
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	Re: Thought I had a turbo 400... (375?) Do you have a pic of the id tag on the passenger side of the trans? __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

03-24-2008, 03:54 AM	#11
SRH916 1975 C-10 Silverado LWB Join Date: Nov 2007 Location: Sacramento, CA Posts: 326	Re: Thought I had a turbo 400... (375?) ill try to get one soon, but i forsure saw the THM 375 on the driveshaft yoke __________________ 1975 LWB C-10 Silverado - Stock - "BIG 10" - 4 Bolt 350 "Brand new" 1200mi - THM-375 "Brand new w/trans cooler" 5000mi 1995 Ford Lightning - Bone Stock - 351W - Vortech??



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