tcwc

Too a tour on old Interstate 80 tonight and I noticed something strange. I was blowing by everyone (stayed in the passing lane for over 20 miles). Now unless everyone else had a light right foot (not usually the case on I80), I'm thining my speedo might be off. I just bought this 86 awhile back, and really don't know if there a rearend gear change or not. The speedo is stock (85MPH). I held it at 65 was was passing everyone.

Without opening up the rearend, is there a method of determing speed of a 5.0 with a T5? Maybe a chart of a certain RPM in a certain gear = MPH???? At the time I didn't think to look at my tach (I was in 5th), but if there is such a chart somewhere I'll have to check it out.

Any ideas?

Thanks for any help.

88blackCONvert

get a friend to cruise the I80 with you at 65 and see what (if any) the difference is between yours and his speeds. easiest way to see if your speedo is right or not

tcwc

Thanks. Yep, thought of that one. Just thought there might be a chart or something like I described that I could reference.

Thanks for the thought.

88blackCONvert

Actually i think there is a chart out there somewhere, but i can't remember where i found it. I stumbled across it when i was looking for my speedo gear when i swapped out my rear gears. Just figured it'd be easier to get a buddy to map your speeds. Keep looking, i know someone knows the formula for it.

r.barn

You can jack up the rear end, put it nuetral, mark the tire and the drive shaft.

Hand turn the tire and count how many times goes around compared to drive shaft.

Thats you gear ratio with out opening rear end

tcwc

Cool info, thanks! Now that you mentioned that, I think I remember reading about that method in the past (20 or something years ago!!). Thanks for the tip!

ikeybmg

usually, unless they were swapped for higher gears, the speedo wouls show faster than actual speeds. if its going faster than it says, that would mean they swapped for higher gears, which i find very strange. maybe your speedo gears are wearing out. or cable bout to break, does the speedo bounce any?

tcwc

yes, it does bounce ... but only at low speed (<20mph). Above 20, it's solid. This whole deal MIGHT just be me (and wishful thinking that the stang has lower gears in the rear).

Another side note on this whole situation. It DOES seem like I run out of 1st gear very quick. As i've said in the past, I've owned an '82, '83, '84, '85, '87, and now and '86. All the years (until this 86, were at least 15 years ago). I don't remember them running out of 1st so fast. This is another reason that got me thinking about someone in the past maybe threw in some lower gears.

You maybe right about the speedo cable. I'm going to take 88blackConvert and r.barn's suggestions (when I get time) and see.

The whole deal might be that I was the only dumb basta*d without a radar detector and just got lucky (although I didn't see any cops)

Thanks for the heads up...

ikeybmg

yea, the lower the gears, the faster the speedo would show.