Speedo gear tooth count

[mysteryman]

Hi guys... . I am short some info on the tooth count of the worm gear on the mainshaft of a getrag 5spd... ... I need this to do the math figuring what pinion tooth count I need to make the speedo read correctly..... or better yet what is the correct # of teeth pinion to use with 235 x 85 x 16" tires when running a getrag 360 5 spd... ...



I referred to the chart in the manual but it was wrong due to the fact they did not recognize the 5spd in the diesel . . The automatics use a different diameter worm gear than the getrag and the gas trucks do not use the ration adaptor... .



In short... I'm lazy today and just want the answer to the question without having to do all the math ... . LOL thx guys

 

[KSommer]

what gears in the rearend?

kent

 

[mysteryman]

oh yea... ... forgot to mention that 3. 55 gears ... thx for asking

what gears in the rearend?

kent

 

[KSommer]

i still don't know fer sure, but i bet you have a competent driveline shop around or mabey a good guy behind the parts couter at the dealer who could get the right gear for ya.

kent

 

[mysteryman]

speedometer drive gear update

I figured it out..... had to remove the worm gear from the trans to get a count... I won't bore you with all the math. The bottom line is this.



On a 2wd with getrag 5spd with the factory installed right hand adaptor.



3. 55 gears and 235x85x16 tires you use a 28 or 29 tooth pinion



4. 10 gears and 235x85x16 tires you use a 30 or 31 tooth pinion



The reason I list 2 #'s for each is because different brand tires have different outside diameters for the same size tire... This should not be the case because the tire size is actual mathematic dimension... It just seems that there is a lot of company's out there that don't use the same ruler as we engineers do. .



Another factor that affects the OD is air pressure and GVW

Hi guys... . I am short some info on the tooth count of the worm gear on the mainshaft of a getrag 5spd... ... I need this to do the math figuring what pinion tooth count I need to make the speedo read correctly..... or better yet what is the correct # of teeth pinion to use with 235 x 85 x 16" tires when running a getrag 360 5 spd... ...



I referred to the chart in the manual but it was wrong due to the fact they did not recognize the 5spd in the diesel . . The automatics use a different diameter worm gear than the getrag and the gas trucks do not use the ration adaptor... .



In short... I'm lazy today and just want the answer to the question without having to do all the math ... . LOL thx guys