Speedometer correction - Saginaw 4 speed

[Mbeef61]

I was out today doing some math to find my transmission gear ratios. I have a 71 stepside 350 with saginaw 4 speed. 3.73 gears 295/50/r15 (26.6") rears. I am trying to correct the speedometer and am not sure how to go about it. I have tried to search but cannot make sense of it.

Turns out it is a "2-line" saginaw 4 speed with gear ratios as follows:

1 - 3.11
2 - 2.20
3 - 1.47
4 - 1

My speedo compared to GPS is 1.3 too fast.

For example:
Speedo says 13, GPS 10
Speedo 39, GPS 30
Speedo 65, GPS 50
Speedo 95, GPS 70

How do I go about correcting this?

[Steeveedee]

You can buy an adapter.

One example, but just a web pick, not a recommendation for them in particular.

https://transmissioncenter.net/produ...dometer-gears/

[Mbeef61]

thanks, looks like I need to determine which I have in there now and get one with less teeth.

How do you remove the speedo gear?

[Steeveedee]

You can just bolt the adapter onto the transmission where the speedo cable goes, then attach the speedo cable to the adapter. But if you want to try a different driven gear, there is a 1/4"-20 (I think) bolt with a tab that keys into the part that is on the trans now and holds the driven gear. Take a look, you will see it. You can only go up or down so much on the driven gear, as it is matched to the drive gear on the output shaft. It's a big enough pain to change all that that the factory has adapters they just pop on to get them close enough.

[Mbeef61]

Like this? I don’t know if this one works for saginaws but is this what you are talking about? I think the slow down 26.7% would get me close

https://transmissioncenter.net/shop/...ratio-adapter/

[Steeveedee]

Yeah, but it's a shame that they cost so much. The company can steer you to the one with the right size threads.

[Keith Seymore]

Ditto on the addition of an adapter.

That 3.11 low gear Saginaw is a nice trans btw.


K

[Mbeef61]

Originally Posted by Keith Seymore

Ditto on the addition of an adapter.

That 3.11 low gear Saginaw is a nice trans btw.


K

Yeah I’m playing with the idea now. It seems you need to remove the shifter etc to get to the speedo gear. It’s like $10-15. The adapter is about $60 more but saves a lot of work. Seems almost worth it haha.

I don’t mind the transmission. It’s no Muncie but it serves its purpose. I like the ratios. Quick off the line. I avoid super hard shifts cuz I know it’s not the strongest thing in the world

[Steeveedee]

I had a 4-speed Saginaw in my '69 Camaro. A hard start or two and something went wrong with it. I had it out and apart a couple of times but couldn't figure it out. That was in '72, and I wasn't all that much of a transmission guy. It would clatter while in gear on hard acceleration, but was OK in 4th. I drove it like that all the way to Illinois from California for my US Navy "A" school, and bought a Muncie 4-speed and put that in while I was at school there.

[Mbeef61]

Originally Posted by Steeveedee

I had a 4-speed Saginaw in my '69 Camaro. A hard start or two and something went wrong with it. I had it out and apart a couple of times but couldn't figure it out. That was in '72, and I wasn't all that much of a transmission guy. It would clatter while in gear on hard acceleration, but was OK in 4th. I drove it like that all the way to Illinois from California for my US Navy "A" school, and bought a Muncie 4-speed and put that in while I was at school there.

Still have the camaro?? Yeah i have heard they don’t like banging gears. Especially reverse they say.

[Steeveedee]

No, sadly, I parted ways with that Camaro in '75. 327 and a 4-speed RS with a tach and gauges. If we only knew, right?