speedo gearing

[DOkkema]

I changed the rear end on my d-350 from a 4. 10 to a 3. 55 I have a 5 speed in the truck can anyone tell me how I can get the speedo corrected it reads slower is there a gear on the trans or something

Thanks Dave

 

[paccool]

You need to change the gear out that is located at the rear of the transmission on the drivers side. (at least with the auto transmission it is)Remove the housing and the gear is inside. Is easy to change. I did the same thing you did, changed from 4. 10 to 3. 54 ratio.



I went to a local speedometer shop with the old gear and told him how far off the speedometer was reading. He looked at the old gear, said you need one with XXX number of teeth instead. (I can't remember how many, sorry. This was about 3 years ago) He didn't even look it up, just walked to a cabinet and pulled one out, said this is the one!



Changed it and all is working fine. Reads dead nuts on.



I think he charged me $18 for the gear.



You should be able to go to a dealer and get one as well if there is one you trust.

 

[DOkkema]

Thanks for the quick help I will look at it tomorrow

Dave

 

[dpuckett]

Dave,

Is there a little gear reduction box coming out of the transmission that the speed sensor hooks up to? Mine have all had one, except for Mom's auto. The box is easier to get and redo than taking the trans housing off and replacing the gear. Not to belittle paccool's idea, just ofering an alternative that worked for me. If you dont havev the box, it may be better to do the gear box. Cost of the box is about $50 from Speedometer Service in Colo Spgs. $80-105 from dealer.



To determine what ratio you need, hook it up directly to the trans screw in thingie, run a known distance (the longer, the more accurate you'll be. Divide the actual distance by the odometer reading. i. e. Mine turned 17. 8 mi on the clock vs 10. 0 on the highway; ratio was . 5617. The guy can make any ratio you need.



Daniel

 

[paccool]

Daniel,



I didn't take the transmission housing off, just the little box that holds the gear. I think there was only one bolt holding it on. The gear is a snap to change out. The only thing here I don't know about is if the manual trannys are set up different.



Stan

 

[dpuckett]

paccool,



Ok, yeah, DUH. I was thinking about the gear on the transmission output shaft. THere has to be another gear driven off that one, (duh, again, Daniel). DOes yours screw directly into the gear housing,or is there a second box the reduces/ increases the rpm of the speed sensor shaft? Mom's auto just screws into the gear housing you referred to; my manuals and 4x4s have had a little box coming out at a 90* angle (2wd) or a straight offset (4x4 out of t-case) box. I'll post pics if I think about it when I get back home to clarify this mudhole I've started up.

Daniel