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12-09-2010, 09:56 AM
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#1 |
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Registered User
Join Date: Dec 2010
Location: Columbia, MO
Posts: 256
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Transmission Code / SPID
Morning Guys--
Will the transmission code on the SPID tell me whether I've got a TH350 or TH400? I need to take a photo and post that up I suppose. Also, I've not been around old transmissions since the days of my '68 Cutlass (2-speed Jetaway) and '74 Camaro (3-spd manual) many moons ago. Would you advise to at least change the fluid/filter or should I leave things alone? I've got some engine oil records but nothing on when the transmission may have been serviced. Shifts very smoothly. Thanks, Mark
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1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport |
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12-09-2010, 10:22 AM
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#2 |
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Registered User
Join Date: Apr 2009
Location: Normal, IL
Posts: 138
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Re: Transmission Code / SPID
Here's what you need to identify your tranny...I had to figure out what I had, too.
http://www.maliburacing.com/auto_tranny_id.htm |
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12-09-2010, 10:26 AM
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#3 |
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Special Order
  
Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,851
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Re: Transmission Code / SPID
No,both will have the M49 code.Weird,but how it was done.Makes no sense.It's like using the same option code for a 350 and a 400.
It wouldn't hurt to change out the fluid and filter,but probably fine as is.Is the color still nice and red?Heat will make it dark and could be a sign the trans has been slipping
__________________
"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ Last edited by special-K; 12-09-2010 at 10:27 AM. |
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12-09-2010, 10:31 PM
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#4 |
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Registered User
Join Date: Dec 2010
Location: Columbia, MO
Posts: 256
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Re: Transmission Code / SPID
It's a 350. Thanks for that link.
__________________
1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport |
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12-10-2010, 12:13 PM
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#5 |
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Registered User
Join Date: Dec 2010
Location: Columbia, MO
Posts: 256
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Re: Transmission Code / SPID
Should have asked this in my initial post. Where can I find the rear-end ratio?
Thanks, Mark
__________________
1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport |
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12-10-2010, 06:26 PM
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#6 |
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its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,690
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Re: Transmission Code / SPID
Some trucks got the car option number (M38) for the TH350, but generally they were all M49 in trucks.
The rear gear, if not listed on the SPID would be the standard ratio for the series/eng/trans. Assuming we are talking about the 72 GMC in your signiture, we now know it has a TH350... what motor does it have? |
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12-10-2010, 06:54 PM
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#7 |
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Old Skool Club
 
Join Date: Jun 2001
Location: Benton, AR "The Heart of Arkansas"
Posts: 10,880
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Re: Transmission Code / SPID
Had a pair of '69's. One had a TH350, and it also had M38 on the SPID. Mine has a TH400 and says M49 on the SPID.
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Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was. |
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12-10-2010, 07:39 PM
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#8 |
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Senior Member
Join Date: Aug 2003
Location: Lubbock, Texas
Posts: 2,443
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Re: Transmission Code / SPID
Most spid use M49 for both,but the firewall will use M38 for the 350 and M49 for 400
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72 Cheyenne Super 80 Silverado Blazer 2wd |
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12-10-2010, 08:14 PM
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#9 |
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Registered User
Join Date: Sep 2001
Location: Fort Wayne, Indiana, USA
Posts: 1,888
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Re: Transmission Code / SPID
Nice catch Jason! I hadn't noticed that.
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12-11-2010, 12:35 AM
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#10 | |
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Registered User
Join Date: Dec 2010
Location: Columbia, MO
Posts: 256
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Re: Transmission Code / SPID
Quote:
__________________
1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport |
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12-11-2010, 05:24 PM
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#11 |
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Registered User
Join Date: Dec 2010
Location: Columbia, MO
Posts: 256
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Re: Transmission Code / SPID
Metal tab on the bottom left of the diff has a 4.10 stamped on it. I'm assuming this is my ratio? It does scream on the highway at 60 mph so I would not be surprised.
__________________
1972 GMC 2500 Custom, 96K miles, Purchased New By My Grandparents 2016 Toyota Tundra TRD Off-Road SR5 1993/2003/2005 Toyota Land Cruisers 2004 Corvette Z06 / 2000 Covette Coupe 2006 Ducati Multistrada 2014 BMW X3 XDrive35i M Sport |
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12-11-2010, 07:50 PM
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#12 |
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its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,690
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Re: Transmission Code / SPID
you got it, a 350/auto in a 3/4 ton would get a 4.10 ratio standard.
It's MUCH better than the 4.57 |
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