Going off of local PD speed checking radar, my speeds looked pretty good after putting on the 33" tires. I was almost dead-on at 45 mph. However, this method is not the most accurate. We all know that radar doesn't work.. especially if you have ever had a speeding ticket.

On our recent off-roading trip, I checked my speed against the others in the convoy, driving trucks with factory tires, and it was suprisingly off by 10-15 mph. While the difference is hardly noticed at low speeds, highway speeds appear to be well below actual speed. I checked the speedo gear chart, seen below, and figured I needed a 32 tooth gear. It only takes one day for the Parts/Service section of your dealer to order this baby, it is $18.

Gears Tire Diameter
33" 32" 31" 30" 29" 28"
3:07 SG26 SG27 SG27 SG28 SG28 SG29
3:55 SG31 SG31 SG32 SG33 SG33 SG34
3:73 SG32 SG32 SG33 SG34 SG34 SG35
4:10 SG34 SG35 SG36 SG37 SG38 SG39
4:56 SG36 SG37 SG37 SG38 N/A N/A

Example: SG34 = speedo gear with 34 teeth

In order to figure out if your t-case requires the short (2.2") or the long (4.3") shaft gear we need to look at the connection. If you have the newer electronic type of connection at the t-case where the speedo gear is you will have the short shaft (1993-2000). If you have a cable type connection at the t-case where your speedo gear is you will have the long shaft (1987-1993). You may want to remove and measure it just to make sure.

Short shaft part numbers (1993-2000)
- 52067629 - 29 tooth
- 52067630 - 30 tooth
- 52067631 - 31 tooth
- 52067632 - 32 tooth
- 52067633 - 33 tooth
- 52067634 - 34 tooth
- 52067635 - 35 tooth
- 52067636 - 36 tooth
- 52067637 - 37 tooth
- 52067639 - 39 tooth
- 52067640 - 40 tooth
- 52067641 - 41 tooth
Long shaft part numbers (1991-1993)
- 2538929 - 29 tooth
- 2538930 - 30 tooth
- 2538933 - 33 tooth
- 2538934 - 34 tooth
- 2538935 - 35 tooth
- 2538936 - 36 tooth
- 2538939 - 39 tooth
- 2538940 - 40 tooth
- 2538941 - 41 tooth
- 2538942 - 42 tooth
Long shaft part numbers (1987-1990)
- 53001492 - 29 tooth
- 53001488 - 41 tooth
- J3212729 - 29 tooth
- J3212730 - 30 tooth
- J3212731 - 31 tooth
- J3212733 - 33 tooth
- J3212734 - 34 tooth
- J3212735 - 35 tooth
- J3212739 - 39 tooth
- J3212740 - 40 tooth

Procedure:

  1. Mark the electrical connector going into the top, rear of the transfer case. This is for ease of reinstallation
  2. Remove the machine screw and retaining clip from the connector. Save this, it needs to be reused.
  3. Slide the connector and old speedo gear out of the transfer case.
  4. Pull the old speedo gear off of the speedogear adaptor.
  5. Make sure that the index marker is aligned for your new gear, newer models will have this etched on the speedogear adaptor.
  6. Push the new speedo gear onto the adaptor.
  7. Insert the adaptor into the transfer case, lining up the mark made previously.
  8. Replace the retaining clip and machine screw.
  9. Go test your speed against a friend in a car.