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 01-06-2007, 06:28 PM   #1
C10 - C90 Bill
Registered User
 
C10 - C90 Bill's Avatar
 
Join Date: Nov 2001
Location: Moneta, VA USA
Posts: 1,093
Looking For Info on 3-Speed Trans Ratios

I was under my '72 C-10 today and wrote down the numbers off my 3-Speed trans. The number located on the main case is 3925847. The trans seems to be original to the truck as the date code reads Feb 20, 1972 (B202).

I'm trying to find out what gear ratios the trans has, especially 1st gear.

Any info would be appreciated.
C10 - C90 Bill is offline   Reply With Quote
Old 01-06-2007, 06:57 PM   #2
kyull67
Keepin' it Inline.
 
kyull67's Avatar
 
Join Date: Nov 2006
Location: Springfield/Kansas City
Posts: 1,824
Re: Looking For Info on 3-Speed Trans Ratios

oops.

Last edited by kyull67; 01-07-2007 at 12:23 PM.
kyull67 is offline   Reply With Quote
Old 01-06-2007, 07:03 PM   #3
WorkinLonghorn
Registered User
 
WorkinLonghorn's Avatar
 
Join Date: Dec 2006
Location: So.Calif.
Posts: 2,212
Re: Looking For Info on 3-Speed Trans Ratios

The standard 3-speed is; 1st= 2.85-1
2nd=1.68-1
Rev=2.95-1
The HD option 3 spd = 1st=3.03-1
2nd=1.75-1
Rev=3.02-1
I don't know which you have but the HD came standard with 350 and BB motors I believe.-cougar
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, 350 ci., NP435CR Trans., 3.73 Dana-60 open. Fancy new horn button. 105,000 miles
WorkinLonghorn is offline   Reply With Quote
Old 01-06-2007, 08:44 PM   #4
Brad
Out of the carpool lane.
 
Brad's Avatar
 
Join Date: Jan 2000
Location: Clark Co, WA
Posts: 5,692
Re: Looking For Info on 3-Speed Trans Ratios

Code H is 3 spd HD Muncie, code K is 3 spd McKinnon, M is 3spd Muncie, and S is Saginaw. There were 2 Saginaws: CS models got the synchromesh with ratios 2.94, 1.68, 1.00, 3.14 rev. CE models got the fully synchronized with ratios 2.85, 1.68, 1.00, 2.95 rev.
__________________

1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red
1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!)
2000 Honda VFR in the faster yellow!
2008 Husqvarna TE-610
2004 Kawasaki Ninja 250

1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...

Brad is offline   Reply With Quote
Old 01-06-2007, 11:02 PM   #5
C10 - C90 Bill
Registered User
 
C10 - C90 Bill's Avatar
 
Join Date: Nov 2001
Location: Moneta, VA USA
Posts: 1,093
Re: Looking For Info on 3-Speed Trans Ratios

Appreciate all the replies.

Just to make it clear, it is a manual trans.

I believe it is not the Heavy Duty type. The truck is a Custom C-10 with a 307 engine and has a synchro first gear.

Why I am asking is, it is a strange set-up. I have what I believe are 3:73 rear gears. When I first got it, I could not go over 60 MPH without it feeling like it was revving too much. I put on 265/75/15 tires on the back and gained about another 5 MPH which made a big difference. But first gear felt too high, even before the tire change. After the tire change, of course, it got a little worse. If I were to guess, it feels like I got a 2.00 or 2:05 first.

Did GM make one with high first gear ratio, like it seems I have?
C10 - C90 Bill is offline   Reply With Quote
Old 01-06-2007, 11:06 PM   #6
Brad
Out of the carpool lane.
 
Brad's Avatar
 
Join Date: Jan 2000
Location: Clark Co, WA
Posts: 5,692
Re: Looking For Info on 3-Speed Trans Ratios

You probably have a 2.85 1st since it's a V8. I'm not sure I understand what you're asking.
__________________

1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red
1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!)
2000 Honda VFR in the faster yellow!
2008 Husqvarna TE-610
2004 Kawasaki Ninja 250

1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...

Brad is offline   Reply With Quote
Old 01-06-2007, 11:12 PM   #7
C10 - C90 Bill
Registered User
 
C10 - C90 Bill's Avatar
 
Join Date: Nov 2001
Location: Moneta, VA USA
Posts: 1,093
Re: Looking For Info on 3-Speed Trans Ratios

Brad, It sounds like I'm supposed to have a 2.85 first, but it don't seem like it. First gear feels too high. It's almost like I'm starting off in 2nd gear.
C10 - C90 Bill is offline   Reply With Quote
Old 01-06-2007, 11:21 PM   #8
Brad
Out of the carpool lane.
 
Brad's Avatar
 
Join Date: Jan 2000
Location: Clark Co, WA
Posts: 5,692
Re: Looking For Info on 3-Speed Trans Ratios

Are you sure you have an original rearend? Could it be that it's been swapped out for a Camaro rearend giving you say, a 2.73 rear gear ratio? To check what ratio you have jack up the rearend and make a mark on the tire and on the driveshaft. Spin the tire 1 revolution and count how many turns it spins the driveshaft. If it's 3 & 3/4 turns its a 3.73, just over 4 turns and it's a 4.10
__________________

1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red
1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!)
2000 Honda VFR in the faster yellow!
2008 Husqvarna TE-610
2004 Kawasaki Ninja 250

1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...

Brad is offline   Reply With Quote
Old 01-06-2007, 11:32 PM   #9
C10 - C90 Bill
Registered User
 
C10 - C90 Bill's Avatar
 
Join Date: Nov 2001
Location: Moneta, VA USA
Posts: 1,093
Re: Looking For Info on 3-Speed Trans Ratios

I've never proved what ratio I have, but I feel pretty certain about it being a 3.73. Check back to my second post, if you would, and you can read about my over-revving on the highway problem.

If GM didn't offer a trans with a much higher first than a 2.85, then it's almost like someone along the line replaced first gear with a much different ratio. Which, I guess is possible. I'll probably just try another trans one day.
C10 - C90 Bill is offline   Reply With Quote
Old 01-07-2007, 12:32 AM   #10
WorkinLonghorn
Registered User
 
WorkinLonghorn's Avatar
 
Join Date: Dec 2006
Location: So.Calif.
Posts: 2,212
Re: Looking For Info on 3-Speed Trans Ratios

Are you used to driving some other vehicle with a four speed? A T-10 truck 4spd has a 3.44 1st.My truck has a N.P.435CR which has a 4.56 1st.And of course the granny low on a 465 is even lower (6.55).But even 2nd in a 465 is still much lower than your 2.85 at 3.58.
If you have the standard 2.85 1st and 3.73 rear and 31" tires,you should be able to hit 43 MPH at 5000 RPM in 1st.-cougar
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, 350 ci., NP435CR Trans., 3.73 Dana-60 open. Fancy new horn button. 105,000 miles
WorkinLonghorn is offline   Reply With Quote
Old 01-07-2007, 11:48 AM   #11
C10 - C90 Bill
Registered User
 
C10 - C90 Bill's Avatar
 
Join Date: Nov 2001
Location: Moneta, VA USA
Posts: 1,093
Re: Looking For Info on 3-Speed Trans Ratios

Cougar, You just about read my mind. I was about to say that myself. I am pretty much used to granny gear 4-Speed and 5-Speed trucks and 10-Speed Road Ranger transmissions.

But,

The half ton pick up I drove daily just before this one was a '66 C-10 which I believe also has a 3.73 rear. Starting off in that truck seemed more normal to me. When I jumped over to the '72 C-10, I could tell a difference. What I need to do next is find out if the '66 trans has a lower first. As you probably know, they are the old style Muncie non-synchro first trannys. Typical of those not holding up real good, I went thru 3 of those trans in the 9 years I had that truck on the road. The last one I put in, was out of a '61 Bel-Air car with a 235 6 cylinder. All 3 trans I used all seem to have the same ratios.

What I need to do next is to find out what those old 3-Speeds had for a first gear ratio and that could possibly answer my question.
C10 - C90 Bill is offline   Reply With Quote
Old 01-07-2007, 12:26 PM   #12
WorkinLonghorn
Registered User
 
WorkinLonghorn's Avatar
 
Join Date: Dec 2006
Location: So.Calif.
Posts: 2,212
Re: Looking For Info on 3-Speed Trans Ratios

Well,unfortunately I only have data for 1969 from the original GM "Truck Data Book" from that year and they only list the two 3-speeds I listed in my first post;regular (2.85-1) and HD (3.03-1).There was also an overdrive unit available on the C-10 with 4.11 rear only,but it has the same 2.85 1st gear.
These two 3-spds were fully sync'd.-cougar
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, 350 ci., NP435CR Trans., 3.73 Dana-60 open. Fancy new horn button. 105,000 miles
WorkinLonghorn is offline   Reply With Quote
Old 01-07-2007, 08:30 PM   #13
C10 - C90 Bill
Registered User
 
C10 - C90 Bill's Avatar
 
Join Date: Nov 2001
Location: Moneta, VA USA
Posts: 1,093
Re: Looking For Info on 3-Speed Trans Ratios

Well it looks like I found my answer. A pretty knowledgable poster on another forum stated that the first gear ratio I have in my old '66 C-10 is a 2.94. Compared to the 2.85 in my '72 C-10 is only a .09 difference, but probably enough for me to notice. Couple that with what Cougar stated about me not being used to higher first gears and it makes pretty much sense.

What I need to do in time is to find one of those HD 3-Speed trannys with the 3.03 first gear.

Appreciate y'all's help!
C10 - C90 Bill is offline   Reply With Quote
Old 01-07-2007, 09:47 PM   #14
Brad
Out of the carpool lane.
 
Brad's Avatar
 
Join Date: Jan 2000
Location: Clark Co, WA
Posts: 5,692
Re: Looking For Info on 3-Speed Trans Ratios

__________________

1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red
1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!)
2000 Honda VFR in the faster yellow!
2008 Husqvarna TE-610
2004 Kawasaki Ninja 250

1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...

Brad is offline   Reply With Quote
Old 01-07-2007, 10:03 PM   #15
WorkinLonghorn
Registered User
 
WorkinLonghorn's Avatar
 
Join Date: Dec 2006
Location: So.Calif.
Posts: 2,212
Re: Looking For Info on 3-Speed Trans Ratios

Actually Bill,there is also a 3-speed listed for the El Caminos that had the 350 or 396 engines (in 1969 anyway) that had a 2.42 1st gear,1.58 2nd,and 2.41 Rev.
Is it possible somebody had one put in a pick-up?-cougar
Just noticed that it was a floor shift though.
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, 350 ci., NP435CR Trans., 3.73 Dana-60 open. Fancy new horn button. 105,000 miles
WorkinLonghorn is offline   Reply With Quote
Old 01-07-2007, 10:10 PM   #16
WorkinLonghorn
Registered User
 
WorkinLonghorn's Avatar
 
Join Date: Dec 2006
Location: So.Calif.
Posts: 2,212
Re: Looking For Info on 3-Speed Trans Ratios

Quote:
What I need to do in time is to find one of those HD 3-Speed trannys with the 3.03 first gear.
There should be lots around.Here's what the 1969 GM "Truck Data Book" says: "A special heavy-duty transmission is included when either the 350 V8 or 396 V8 engines are ordered..." "This unit is also standard on all 4-wheel drive (KA 10-20) engine applications."-cougar
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, 350 ci., NP435CR Trans., 3.73 Dana-60 open. Fancy new horn button. 105,000 miles

Last edited by WorkinLonghorn; 01-07-2007 at 10:11 PM.
WorkinLonghorn is offline   Reply With Quote
Old 01-08-2007, 06:33 AM   #17
C10 - C90 Bill
Registered User
 
C10 - C90 Bill's Avatar
 
Join Date: Nov 2001
Location: Moneta, VA USA
Posts: 1,093
Re: Looking For Info on 3-Speed Trans Ratios

Cougar, It sure seems like I got a 2.42. I'd like to prove it one way or another and I'm wondering if the numbers I posted in my first post would tell us anything.

Also wondering how to tell an HD 3-Speed compared to a Standard one.

I can find plenty of info on 4-Speeds, but the 3-Speed info is a little harder to find out there.
C10 - C90 Bill is offline   Reply With Quote
Old 01-08-2007, 08:15 AM   #18
WorkinLonghorn
Registered User
 
WorkinLonghorn's Avatar
 
Join Date: Dec 2006
Location: So.Calif.
Posts: 2,212
Re: Looking For Info on 3-Speed Trans Ratios

Quote:
I'm wondering if the numbers I posted in my first post would tell us anything.
I'll look it up for you the next time I go by the "Auto Books" store in Burbank. There's a book there called "Chevy ID Numbers" Or "Chevy by the Numbers".
Personally I am not familliar with the differences in appearance or in how to ID transmissions etc. I'm somewhat familiar with auto-trans stuff because I used to manage a couple AAMCOs way back when.-cougar
__________________
'69 GMC C2500 Custom Camper, 8 1/2' bed, 350 ci., NP435CR Trans., 3.73 Dana-60 open. Fancy new horn button. 105,000 miles
WorkinLonghorn is offline   Reply With Quote
Old 01-08-2007, 09:51 AM   #19
Brad
Out of the carpool lane.
 
Brad's Avatar
 
Join Date: Jan 2000
Location: Clark Co, WA
Posts: 5,692
Re: Looking For Info on 3-Speed Trans Ratios

It would be much easier to identify if you posted a picture of your transmission. We could tell you exactly what you have. And unless someone put in a Muncie car transmission, there's no way you have a 2.42 1st gear.
__________________

1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red
1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!)
2000 Honda VFR in the faster yellow!
2008 Husqvarna TE-610
2004 Kawasaki Ninja 250

1967 C-10 SWB 'Six Appeal'-Gone but not forgotten...

Brad is offline   Reply With Quote
Reply

Bookmarks

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 -5. The time now is 08:33 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Copyright 1997-2013 67-72chevytrucks.com