What transmission fluid to top off.

[Mjcre]

I’m installing a new speedo cable and speedo gear—hopefully that will fix my bouncing speedo and 15-20 mph difference with my rear gear change.

I’ve never done anything with the 727 transmission since I have owned my RR. I am wondering what transmission fluid I need to use to top off the fluid from what I will lose when changing the speedo gear? I have no idea what fluid was used prior to me owning the vehicle. Will mixing hurt?

It looks like from some other posts that I will lose some fluid but not sure how much. Is there a way to change out the speedo gear with no lost fluid or minimal loss? If not possible, how much fluid should I expect to lose?

Thanks in advance for evryone’s help.

 

[oldbee]

Sitting level on the ground? Maybe half a coffee cup on the ground at most, don't worry about it. I've always used TypeF but there'll be other opinions I'm sure.

 

[PRND21]

If you don’t know what is in it and how long it’s been in there, why not change the fluid while you’re under there?

 

[Billccm]

If you don’t know what is in it and how long it’s been in there, why not change the fluid while you’re under there?

Good time to drain and swap the filter. My transmission guy recommends atf+4 for any mopar, old or newer.