Topic: 4Banger Jeep Speed (Ha! :)

[Mozman68]

29,30,33,34,35,37 is all I have, seems the 39 and 41 are pretty popular with the lower gearsets.  The long shaft/short shaft are interchangeable, just swap the gear onto whichever length shaft you need.  I would highly recommend Tacoma Speedometer at the above link.

I would also recommend this Universal Speedometer Signal Interface from Dakota Digital, pretty cheap ($80) and can adjust your speedo for any tire size or gear ratio, and for any drivetrain/ECM combination for that matter.  I run one, works great as I run two different sizes of tires between my road and offroad tires, adjusting the speedo is just a few pushes of the button below the dash.  I also HAD to run one since I installed a super-short SYE and it no longer uses a speedo gear.  http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=287/home_id=59/mode=prod/prd126.htm

I still haven't installed this...do you mind doing a quick write up of how you wired it in so I'm not starting from scratch?? 

[vprsrul]

I put in the 38 tooth today and it worked fine right off the bat.  There's a little metal bump at 6 o'clock on the VSS port opening on the transfer case.  You just apparently need to line up your teeth-range numbering on the VSS -- mine was 31(2?)/38 -- directly over that little metal bump and you're all set.  I also put in a new gasket, then reset battery.  Feels like its driving better already. 

does correcting your speedo actually optimize engine performance? 

[jfrabat]

does correcting your speedo actually optimize engine performance? 

Yes, the ECU uses the speed data in its calculations...

[Jeffy]

I still haven't installed this...do you mind doing a quick write up of how you wired it in so I'm not starting from scratch?? 

It's not that hard.  I talked a friend through it over the phone once. 

[dwtaylorpdx]

I had a guy want me to talk him through a timing chain on the phone,
he normally could not change his own sparkplugs....

I told him to go to Autozone rent a puller and call me
when he had the dampener off the engine...............
He called me like 3 weeks later.....
 
Dave

[vprsrul]

Yes, the ECU uses the speed data in its calculations...

awesome,  since I run 33's and stock gearing without a corrected speedo I wonder if it would be worth while till I put some gears in it down the road.

[dwtaylorpdx]

Most people that do recal the speedo notice a decent little bump in mileage,
as well as a smoother running engine under load. Not earth shattering but a nice tweek.

Off to add it to the mod list... :)

Dave

[jfrabat]

awesome,  since I run 33's and stock gearing without a corrected speedo I wonder if it would be worth while till I put some gears in it down the road.

I would recommend to do it, because it is cheap and quick...

[vprsrul]

I would recommend to do it, because it is cheap and quick...

Anywhere in particular you recommend getting it from?  I will definatly do it as the jeep gets driven quite frequently,  seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...

[chrisfranklin]

I put in the 38 tooth today and it worked fine right off the bat.  There's a little metal bump at 6 o'clock on the VSS port opening on the transfer case.  You just apparently need to line up your teeth-range numbering on the VSS -- mine was 31(2?)/38 -- directly over that little metal bump and you're all set.  I also put in a new gasket, then reset battery.  Feels like its driving better already. 

And I also checked the speedo vs. gps  at lower speeds and a variety of highway speeds -- 55-80 -- yesterday and it looked like the speedo and gps were fairly dead on. 

[jfrabat]

Anywhere in particular you recommend getting it from?  I will definatly do it as the jeep gets driven quite frequently,  seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...

Try dakota...  They can even custom make if you need them to (I didnt go this way when I had 31's and 4.88; I know I was going to 33's soon and was not willing to spend the dough, but they offered to make it).

[chardrc]

Anywhere in particular you recommend getting it from?  I will definatly do it as the jeep gets driven quite frequently,  seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...

the tbi computer doesn't read the speed (pre91)... so it wont change performance just the speedometer reading..

[sharpxmen]

Anywhere in particular you recommend getting it from?  I will definatly do it as the jeep gets driven quite frequently,  seems the 89 model speedo gear is tough to find, every part place I go to has it for cj's and 91 and up...

i was told here that the gears are the same just the shaft is different (shorter for 91+) and that you can put the new gear on the old shaft

[vprsrul]

the tbi computer doesn't read the speed (pre91)... so it wont change performance just the speedometer reading..

Guess I am going to leave it alone if thats the case... I will just use my gps for a speedometer.. Thanks for the info!

i was told here that the gears are the same just the shaft is different (shorter for 91+) and that you can put the new gear on the old shaft

good to know thankyou!

[C.Redbeardd]

the tbi computer doesn't read the speed (pre91)... so it wont change performance just the speedometer reading..

Yes, when I replaced my transfer case I dont think the speedo cable got hooked up correctly because my speedo isnt working... Anyway, that explains why I havent noticed any change in performance. Thanks.