Hey guys I recently got my car regeared to 4:88 and had front and rear lockers installed on 37" tires. First drive on the highway im able to take the vehicle to about 60MPH on the highway @ around 3500 rpm. Does this seem normal? 60 mph at 3500 RPM?!?
2F,4:88,37'
- Thread starter SteadyT3ddy
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Take an actual measurement of your tires and post it up.
No, that does not sound right. Should be around 2650. In fact, if you were really going 60 mph @ 3500 rpm with 4.88 gears, your tire size would be 28". I suspect that you were going faster than 60 mph due to speedo error from the larger size. So with 37s, at 3500 rpm, you should be going 79 mph. That seems weird too since I would think you would know you were going way past 60. Time for a GPS or phone app. And here's a calculator (one of millions):
Tire Size, RPM, Speed, and Differential Ratio Calculator
Tire Size, RPM, Speed, and Differential Ratio Calculator
- Thread starter
- #4
I've confirmed Via gps/Iphone app. Both show mph at 35xx rpm.
Tire size is 37x12.5r16.5 Wranger MTR
Note: I had the work done at a very reputable gear shop, I personally have had nothing but problems with this shop
Tire size is 37x12.5r16.5 Wranger MTR
Note: I had the work done at a very reputable gear shop, I personally have had nothing but problems with this shop
The chart below is at 65 mph.
3500 rpm at 60mph with 37" tires & 4:88 gears is not possible.
3500 rpm at 60mph with 37" tires & 4:88 gears is not possible.
- Thread starter
- #6
Not possible in what way.. Can you explain please?
^^
The chart above shows RPMs at 65 mph for different tire sizes and gear combinations. These values are written in stone and can not be changed due to physics.
If your cruiser truly is traveling at 60 mph with 37" tires. The gears installed were not 4:88s. Either that, or the tach is way off and the engine isn't spinning at 3500 rpm.
Is it really 3500 RPM? Tach?
The chart above shows RPMs at 65 mph for different tire sizes and gear combinations. These values are written in stone and can not be changed due to physics.
If your cruiser truly is traveling at 60 mph with 37" tires. The gears installed were not 4:88s. Either that, or the tach is way off and the engine isn't spinning at 3500 rpm.
Is it really 3500 RPM? Tach?
- Thread starter
- #9
No. I just got off the phone with the shop and the owners and he insisted that what ever is stated on the invoice is whats been done, and the problem is with my car.
- Thread starter
- #10
The tach shows 3500.. After driving it for 2 min on the highway I feel like the motor is about to blow!
So we know it's really running at 3500 RPM at 60.
Did you check your transfer lever as 90Fj suggested?
Is it possible that it's in 4Lo?
Did you check your transfer lever as 90Fj suggested?
Is it possible that it's in 4Lo?
cwwfj60
Supporting Vendor
whatever your problem is you should back off if your motor feels like it is about to blow, are you running factory ignition or hei gm distributor? perhaps there is a tach problem? either way like everyone said it doesn't make sense.
if it was in 4lo I think you wouldn't be able to pass 45mph or so but thats a guess. Definitely worth checking.
and please stop calling it a car....
if it was in 4lo I think you wouldn't be able to pass 45mph or so but thats a guess. Definitely worth checking.
and please stop calling it a car....
- Thread starter
- #13
Vehicle in 2hi.
Ignition is all stock.
Ignition is all stock.
cwwfj60
Supporting Vendor
I was going to recommend the same thing but I believe running 529s would require opening up the housing and is rare for anything on a street truck, and that ring gear is significantly bigger. I just couldn't imagine somebody screwing that up, but it would make sure you got the 488s
- Thread starter
- #16
I think thats my only option. What is the tire/DS process? Turn tire untill makes 360 Rotation while counting the rotations on the drive shaft? then divide?
cwwfj60
Supporting Vendor
yes a 488 would 4.88 rotations of the driveshaft/pinion flange to one on the tire/ring gear. make a mark with white out or a paint pen on the top of the pinion flange or a reference spot you can see easily, I'd make a mark on the pinion dust shield (behind the flange) and a mark on the 3rd housing. then make a mark at the top of the tire and count as you do 1 complete rotation of the tire. You will either get close but less than 5 (4.88) revolutions on the driveshaft or just past 5 (5.29). or perhaps something else......
Of course this seems bizarre to me, hopefully you got what you paid for....
Of course this seems bizarre to me, hopefully you got what you paid for....
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Are you in 3rd gear or 4th gear?
Also I would definite check if you are in low range.
Also I would definite check if you are in low range.
- Thread starter
- #20
I just cant wait to get off work and rush home to check it out. I will be honest i have a little vibration when letting which i think is a bad throw out bearing, other then that car drives fine.
