speedo gear in the tranny, 70

[John Fulton]

Re: 70 tranny speedo gears / adapters

Thanks Wayne. I am not sure the gear (which I lost) was red, I glanced at it and my thought was it was burgundy. Based on all the feedback I think it must have been brown, but maybe faded a little or with oil on it or something it appeared to me to be burgandy. I noticed you described the adaptor as 90 deg. with a grease nipple as well-leading me to order a brown gear, red for direct connect, and the green-one of those outta work. I tried everything I could to fish the gear out of the lower tranny. The internal worm gear in the tranny blocks the "fishing". I studied the exploded view of the m-20 and came to the conclusion you did that it could interfere with reverse. I think at this time I am going to leave it, so far it seems to be working just fine-what do you think the signal would be that it is time to pull the tranny and overhaul (it will be out anyway). I am wondering since the brown gear is nylon, if it got caught in the reverse gear it would be chewed up and disintegrate.

[John Fulton]

Re: 70 tranny speedo gears / adapters

Thanks Wayne. I am not sure the gear (which I lost) was red, I glanced at it and my thought was it was burgundy. Based on all the feedback I think it must have been brown, but maybe faded a little or with oil on it or something it appeared to me to be burgandy. I noticed you described the adaptor as 90 deg. with a grease nipple as well-leading me to order a brown gear, red for direct connect, and the green-one of those outta work. I tried everything I could to fish the gear out of the lower tranny. The internal worm gear in the tranny blocks the "fishing". I studied the exploded view of the m-20 and came to the conclusion you did that it could interfere with reverse. I think at this time I am going to leave it, so far it seems to be working just fine-what do you think the signal would be that it is time to pull the tranny and overhaul (it will be out anyway). I am wondering since the brown gear is nylon, if it got caught in the reverse gear it would be chewed up and disintegrate.

[Joe L.]

Re: 70 tranny speedo gears / adapters

John and Gary

I mis-spoke in my previous post regarding one point: the original speedometer DRIVE gear for your car IS GM #3924098. This gear is now known as GM #6261794. Both the 3924098 and the 6261794 are IDENTICAL; I have NOS examples of them both.

To summarize, briefly, then: your car was originally equipped with DRIVE gear GM #3924098; DRIVEN gear GM #3860341( a "brown" color coded gear of 18 tooth configuration and now known as GM #3987918) and speedometer adapter GM #6477965(now known as GM #1565208). You can keep this configuration by replacing any needed parts with those part numbers that I've mentioned.

Or, you can convert to the 1969 configuration. To do this, all you need to do is to replace the speedometer DRIVEN gear with GM #3860345( a "green" color-coded gear of 22 tooth configuration) and eliminate the speedometer adapter. The GM # 3860345 gear is completely compatible with your GM #3924098 DRIVE gear. First, though, make sure that your speedomter cable is long enough to allow direct connection to the tailshaft speedometer cable fitting. If it's not, you'll have to retain the 1970 configuration or change the cable and casing assembly(which is a great pain).

Incidentally, the other adapters mentioned, GM #6477964 is now known as GM #1565202 and is still available. GM #6477966 is now known as "discontinued".

[Joe L.]

Re: 70 tranny speedo gears / adapters

John and Gary

I mis-spoke in my previous post regarding one point: the original speedometer DRIVE gear for your car IS GM #3924098. This gear is now known as GM #6261794. Both the 3924098 and the 6261794 are IDENTICAL; I have NOS examples of them both.

To summarize, briefly, then: your car was originally equipped with DRIVE gear GM #3924098; DRIVEN gear GM #3860341( a "brown" color coded gear of 18 tooth configuration and now known as GM #3987918) and speedometer adapter GM #6477965(now known as GM #1565208). You can keep this configuration by replacing any needed parts with those part numbers that I've mentioned.

Or, you can convert to the 1969 configuration. To do this, all you need to do is to replace the speedometer DRIVEN gear with GM #3860345( a "green" color-coded gear of 22 tooth configuration) and eliminate the speedometer adapter. The GM # 3860345 gear is completely compatible with your GM #3924098 DRIVE gear. First, though, make sure that your speedomter cable is long enough to allow direct connection to the tailshaft speedometer cable fitting. If it's not, you'll have to retain the 1970 configuration or change the cable and casing assembly(which is a great pain).

Incidentally, the other adapters mentioned, GM #6477964 is now known as GM #1565202 and is still available. GM #6477966 is now known as "discontinued".

[Joe L.]

CORRECTION---AGAIN!

John-----

I am extremely sorry, but I still posted some incorrect information. You cannot use the 3860345 with your speedometer drive gear. You would have to change your drive gear to the GM #6261795(current version of the 3924097 drive gear). That's impractical, so your best bet would be to stay with the adapter even if you have to replace it. Sorry again for the misinformation---I try hard to give the straight story, but I messed up on this one. Unforgiveably, TWICE!!!

[Joe L.]

CORRECTION---AGAIN!

John-----

I am extremely sorry, but I still posted some incorrect information. You cannot use the 3860345 with your speedometer drive gear. You would have to change your drive gear to the GM #6261795(current version of the 3924097 drive gear). That's impractical, so your best bet would be to stay with the adapter even if you have to replace it. Sorry again for the misinformation---I try hard to give the straight story, but I messed up on this one. Unforgiveably, TWICE!!!

[John Fulton]

Re: CORRECTION---AGAIN!

No problems, I replaced the brown 18 tooth gear and reconnected the adaptor etc. and all is well and original. I just hope the one that fell into the case does not come back to haunt me.

[John Fulton]

Re: CORRECTION---AGAIN!

No problems, I replaced the brown 18 tooth gear and reconnected the adaptor etc. and all is well and original. I just hope the one that fell into the case does not come back to haunt me.

[Joe L.]

Re: CORRECTION---AGAIN!

John-----

I really doubt that the gear will be a problem. It is a relatively soft, nylon gear and it has no metal core of any sort. If it should get into the gears, I suspect that it would just be chewed to bits without harming anything. Certainly, it is FAR softer than any of the trans internal components.

[Joe L.]

Re: CORRECTION---AGAIN!

John-----

I really doubt that the gear will be a problem. It is a relatively soft, nylon gear and it has no metal core of any sort. If it should get into the gears, I suspect that it would just be chewed to bits without harming anything. Certainly, it is FAR softer than any of the trans internal components.