Speedo only goes to 85, what happens if I pass 90?
#1
Member
Thread Starter
Speedo only goes to 85, what happens if I pass 90?
Driving home today, a Mopar charger wanted to play on the highway. I was willing to oblige, but I had to back off at 85 because around the 90mph mark, my speedometer needle will be touching the trip reset pin. It raised the question of what would happen if I were to go 95-100 mph. Would the needle break? Would it just float against the pin?
Obviously I need to upgrade to a higher mph speedometer, in case I ever meet Mr. Mopar again 😜. But I figured it probably would be a good idea to know what would happen with my current speedometer. Anybody have any insight? I'm genuinely curious, just not enough to risk breaking something, haha.
Obviously I need to upgrade to a higher mph speedometer, in case I ever meet Mr. Mopar again 😜. But I figured it probably would be a good idea to know what would happen with my current speedometer. Anybody have any insight? I'm genuinely curious, just not enough to risk breaking something, haha.
#2
Member
iTrader: (3)
Re: Speedo only goes to 85, what happens if I pass 90?
Driving home today, a Mopar charger wanted to play on the highway. I was willing to oblige, but I had to back off at 85 because around the 90mph mark, my speedometer needle will be touching the trip reset pin. It raised the question of what would happen if I were to go 95-100 mph. Would the needle break? Would it just float against the pin?
Obviously I need to upgrade to a higher mph speedometer, in case I ever meet Mr. Mopar again 😜. But I figured it probably would be a good idea to know what would happen with my current speedometer. Anybody have any insight? I'm genuinely curious, just not enough to risk breaking something, haha.
Obviously I need to upgrade to a higher mph speedometer, in case I ever meet Mr. Mopar again 😜. But I figured it probably would be a good idea to know what would happen with my current speedometer. Anybody have any insight? I'm genuinely curious, just not enough to risk breaking something, haha.
The following 2 users liked this post by Degweiser:
Lurbie (07-19-2019), NoEmissions84TA (07-19-2019)
#6
Supreme Member
iTrader: (2)
Re: Speedo only goes to 85, what happens if I pass 90?
… It would be bad… Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.
No, wait, I think it's OK. It just goes past 90. Dang, where are my notes...
No, wait, I think it's OK. It just goes past 90. Dang, where are my notes...
The following users liked this post:
Lurbie (07-19-2019)
Trending Topics
#8
Supreme Member
iTrader: (58)
Re: Speedo only goes to 85, what happens if I pass 90?
I'm just happy to see Fez is still getting work.
So seriously... Thirdgens with speed rated tires from the factory, don't have any limiting controls. When you get into the later EFI cars without Z rated tires you see they don't have the 140mph clusters, and if you hold the WHAAAAAAAAAAAA peddle long enough, when the needle gets to 115mph or so, you'll feel the brick wall and the car slowing down suddenly. After it drops down it'll let you push it back to 115, but at that point the ECM presumably cuts fuel and forces you to stop accelerating. Getting around it, is another topic, but if you want to know what happens when you put a 140 cluster into a 85mph car...
Sorta depends on the car. The old dual needle speedo in my 83 would roll past 85, and wrap around into the KM half of the scale. No trip odometer, no ecm control, with more then 14hp maybe it would have just kept spinning?
Btw, round these parts, late model Chargers are Po Lease. Saw one this weekend, think it was Junction City PD, was hard to tell because it was all black with black windows, all the gear behind the grill or inside behind glass and the PD/Call 911 markings were all done in flat black. Ergo, watch your cornhole.
So seriously... Thirdgens with speed rated tires from the factory, don't have any limiting controls. When you get into the later EFI cars without Z rated tires you see they don't have the 140mph clusters, and if you hold the WHAAAAAAAAAAAA peddle long enough, when the needle gets to 115mph or so, you'll feel the brick wall and the car slowing down suddenly. After it drops down it'll let you push it back to 115, but at that point the ECM presumably cuts fuel and forces you to stop accelerating. Getting around it, is another topic, but if you want to know what happens when you put a 140 cluster into a 85mph car...
Sorta depends on the car. The old dual needle speedo in my 83 would roll past 85, and wrap around into the KM half of the scale. No trip odometer, no ecm control, with more then 14hp maybe it would have just kept spinning?
Btw, round these parts, late model Chargers are Po Lease. Saw one this weekend, think it was Junction City PD, was hard to tell because it was all black with black windows, all the gear behind the grill or inside behind glass and the PD/Call 911 markings were all done in flat black. Ergo, watch your cornhole.
#9
Senior Member
iTrader: (8)
Join Date: Aug 2011
Location: Texas
Posts: 661
Likes: 0
Received 7 Likes
on
7 Posts
Car: 91 Firebird/88 Firebird/91 Formula
Engine: V6 3.1/V8 5.0/V8 5.0
Transmission: 4L60/700R4/4L60
Axle/Gears: 3.23/2.73/2.73
Re: Speedo only goes to 85, what happens if I pass 90?
Used to have an '84 Chrvy Chevette, standard with four gears, that had a speedometer that only went to 90. Drove it on the Autobahn for about a year and half and the speedometer would peg at 90 while the accelerator would go further. I would usually keep up with traffic.
#10
Member
Thread Starter
Re: Speedo only goes to 85, what happens if I pass 90?
Haha, my first thought when I saw him was that he was a cop... but the cops around here don't have custom mag wheels, blue-tipped chrome dual exhaust or a big ol' Mopar logo on the front fender. They're just not that sneaky, lol.
I've always backed off around 85 mph because years ago a friend had a Ford Probe he was restoring and building to race (don't ask me why, lol). He had his gauge cluster sitting out and another friend began screwing around with it, notably the pin that connected the speedo to the cable. He cranked it all the way over to the end, where there was a little stopper peg on the speedo, and the needle broke off. Given that my Trans Am can easily hit about 90 without me even having the pedal to the floor, I kind of figured the folks at GM would have made sure that didn't happen... but I didn't want to find out I was wrong the hard "oh crap, now that's broken!" way.
And the 80's movie references... love it. You guys are my kinda people, lol. Thanks for all the input, glad to at least put that question to bed!
I've always backed off around 85 mph because years ago a friend had a Ford Probe he was restoring and building to race (don't ask me why, lol). He had his gauge cluster sitting out and another friend began screwing around with it, notably the pin that connected the speedo to the cable. He cranked it all the way over to the end, where there was a little stopper peg on the speedo, and the needle broke off. Given that my Trans Am can easily hit about 90 without me even having the pedal to the floor, I kind of figured the folks at GM would have made sure that didn't happen... but I didn't want to find out I was wrong the hard "oh crap, now that's broken!" way.
And the 80's movie references... love it. You guys are my kinda people, lol. Thanks for all the input, glad to at least put that question to bed!
The following users liked this post:
Lurbie (07-19-2019)
#15
Member
Thread Starter
#16
Senior Member
Join Date: Jan 2019
Posts: 571
Received 482 Likes
on
233 Posts
Car: 1989 Firebird GTA
Engine: Motown Aluminum 427
Transmission: TH400/GVO
Axle/Gears: Dana 44 IRS 3.75:1
Re: Speedo only goes to 85, what happens if I pass 90?
added extra light for the midnight run.... actually 3 a.m. run.... too bright, zeroing in on the right intensity...
#17
Supreme Member
iTrader: (1)
Join Date: Feb 2017
Location: Meriden, CT 06450
Posts: 4,034
Received 514 Likes
on
430 Posts
Car: 84 TA orig. 305 LG4 "H" E4ME
Engine: 334 SBC - stroked 305 M4ME Q-Jet
Transmission: upgraded 700R4 3200 stall
Axle/Gears: 10bolt 4.10 Posi w Lakewood TA Bars
Re: Speedo only goes to 85, what happens if I pass 90?
We really do need that LIKE button. Great comment!
A cable driven mechanical speedometer has a magnetic coupling. So if you "pin" the needle, nothing bad happens.
It's not like overwinding a clock or wristwatch until it goes "pop" and never works again.
A cable driven mechanical speedometer has a magnetic coupling. So if you "pin" the needle, nothing bad happens.
It's not like overwinding a clock or wristwatch until it goes "pop" and never works again.
Last edited by NoEmissions84TA; 04-20-2019 at 07:02 PM.
#19
Junior Member
Join Date: Jan 2017
Location: Auckland
Posts: 25
Likes: 0
Received 2 Likes
on
2 Posts
Car: 1984 Trans Am
Engine: LG4 305 4bbl
Transmission: 700R4
Axle/Gears: 3.23 LSD
Re: Speedo only goes to 85, what happens if I pass 90?
I'm forever tempted by Hawks' 160MPH speedo.......but they're bloody expensive and I'm unsure about taking the cluster out anyway.........
#23
Senior Member
Join Date: Jan 2019
Posts: 571
Received 482 Likes
on
233 Posts
Car: 1989 Firebird GTA
Engine: Motown Aluminum 427
Transmission: TH400/GVO
Axle/Gears: Dana 44 IRS 3.75:1
Re: Speedo only goes to 85, what happens if I pass 90?
[QUOTE=John in RI;6298231]How did you calibrate that Speedo Head to be accurate to the custom face-plate ?
Long story, but the key piece is from Dakota.
Long story, but the key piece is from Dakota.
The following 2 users liked this post by 427seven:
Bow_Tied (07-19-2019), kenferrell (07-22-2019)
#25
Member
iTrader: (1)
Join Date: Jan 2017
Location: Dekalb, Il
Posts: 191
Likes: 0
Received 2 Likes
on
2 Posts
Engine: 3.1 V6
Transmission: 700R4
Axle/Gears: No idea
Re: Speedo only goes to 85, what happens if I pass 90?
Nothing. You just won't know how fast you're going. If I'm wot I'll be on the bottom of 4th gear when I hit 85. I bought a gauge off eBay with a speedo for 160 just to know how fast I am going. I took it to 120 the other day.
Thread
Thread Starter
Forum
Replies
Last Post