Rear End/Speedometer Gear Question August 09, 2010, 12:57:42 PM I'm sure this question has been asked, but a search didn't show me what I was looking for.When I swapped in my 87 thunderbird engine and AOD tranny from the car, I left the stock rear end. It is a one leg, 3.08 rear end, which came mated to the 1988 thunderbird 3.8lv6.I have a vss signal error message when I run codes, and I'm guessing I have the wrong speedometer gear, so either vss thinks the car is going faster or slower. Having a 3.08 rear as opposed to the 2.73 limited slip rear the v8 came with, I would assume the speedometer would read higher than my actual speed, correct? What gear would I need to put in the tranny to make it accurate for the 3.08 rear? Is it hard to change a speedo gear? Are they expensive? Quote Selected
Rear End/Speedometer Gear Question Reply #1 – August 09, 2010, 01:15:53 PM Scroll down past the ring and pinion sets and there should be a chart that will be helpful for you. :DChart Quote Selected
Rear End/Speedometer Gear Question Reply #2 – August 09, 2010, 01:36:58 PM this might also help if you have done gear and tire size changehttp://www.accuautoparts.com/calculatorfin.jsp Quote Selected
Rear End/Speedometer Gear Question Reply #3 – August 09, 2010, 01:58:58 PM if needed i have a set of 2 speedo gears im not using i could sell ya on the cheap. bought em for my 84 that had the v8 with the 3.08 rear end. Quote Selected
Rear End/Speedometer Gear Question Reply #4 – August 09, 2010, 02:40:40 PM Quote from: ThunderbirdSport302;331277Scroll down past the ring and pinion sets and there should be a chart that will be helpful for you. :DChartI have the automatic...? Quote Selected
Rear End/Speedometer Gear Question Reply #5 – August 09, 2010, 05:58:07 PM the far right part of the chart is for autos...... with you having the 87 AOD,depends on what drive gear you have in your auto trans, a 7 tooth or 8 toothbut from what it looks like to me.....if you have the 7t drive gear you need the 18T Gray C7SZ-B <-- that is an obsole numberchances are this would be more of your set up8t drive gear and you would need the 20T Orange C8SZ-B Quote Selected
Rear End/Speedometer Gear Question Reply #6 – August 09, 2010, 06:41:41 PM If it's a T-bird/Cougar AOD then you have the 8 tooth drive gear. Quote Selected
Rear End/Speedometer Gear Question Reply #7 – August 10, 2010, 08:57:31 PM I answered in the misc tech as well but for everyone, THE SPEED SENSOR COULD CARE LESS WHICH REAR END OR WHAT GEAR IS IN THE TRANSMISSION....NOW since you have a '87, there is no wiring connection to the EEC from the speed sensor... Of course this assumes you've swapped a '87 harness... Quote Selected
Rear End/Speedometer Gear Question Reply #8 – August 11, 2010, 07:55:24 PM I was wondering why the hell a different gear ratio would throw a code? I always learn something new though. LOL Quote Selected
Topic: Rear End/Speedometer Gear Question (Read 1335 times)
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