How many teeth
Thread Starter
Pro
Joined: Apr 2001
Posts: 591
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From: Morinville Alberta
How many teeth
I just swaped my rear end to a 4.11 from a 3.08 and what a difference
but apparently I am allways doing 60 mph around town so I have a question what drive gear should I put into this tranny to be accurate.
I have as I said a 4.11 rear end ratio with a TH350 tranny and the tire size is 235 60 15's could any one out there take the guess work out of this for me
Thanks. :seeya
but apparently I am allways doing 60 mph around town so I have a question what drive gear should I put into this tranny to be accurate.
I have as I said a 4.11 rear end ratio with a TH350 tranny and the tire size is 235 60 15's could any one out there take the guess work out of this for me
Thanks. :seeya
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: How many teeth (Aaron76)
http://www.prestage.com/carmath/ check this link out. they have some calculators there that may help you
FYi the th350 has 1 to 1 ratio in 3rd gear.
[Modified by Jvette73, 1:25 AM 8/19/2002]
FYi the th350 has 1 to 1 ratio in 3rd gear.
[Modified by Jvette73, 1:25 AM 8/19/2002]
Melting Slicks
Joined: Aug 2000
Posts: 2,310
Likes: 1
Re: How many teeth (Aaron76)
Jvette73, nice site; it's been bookmarked :yesnod:
Aaron76, I started to put in a formula from the June Corvette Fever where they answered a similar question in their Tech Line section. It looks like they provided an answer with two variables though. In addition to the number of teeth needed in the driven gear, they talk about the number of teeth in the drive gear. If you have trouble with the equation on Jvette73's Web site and want me to, I'll post their reply. It would also be interesting to see if you come out needing 33% more teeth in the gear.
Please keep us informed.
Aaron76, I started to put in a formula from the June Corvette Fever where they answered a similar question in their Tech Line section. It looks like they provided an answer with two variables though. In addition to the number of teeth needed in the driven gear, they talk about the number of teeth in the drive gear. If you have trouble with the equation on Jvette73's Web site and want me to, I'll post their reply. It would also be interesting to see if you come out needing 33% more teeth in the gear.
Please keep us informed.
Thread Starter
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Joined: Apr 2001
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From: Morinville Alberta
Re: How many teeth (jerryp58)
Hey bud
If you could post that reply that would be great.
One more thing, You talk about the "Drive gear" Is that the one you can pull out and is plastic or is there another gear that meshes with this one inside the tranny and if so how do you change that one
Thanks.
If you could post that reply that would be great.
One more thing, You talk about the "Drive gear" Is that the one you can pull out and is plastic or is there another gear that meshes with this one inside the tranny and if so how do you change that one
Thanks.
Burning Brakes
Joined: Dec 2000
Posts: 795
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From: Madison MS
Re: How many teeth (Aaron76)
The drive gear is the one on the tailshaft of the transmission. You shouldn't have to replace it. Go to the Chevy dealership and tell them what trans you have as well as the rear-end gear ratio. They can give you the correct gear. This doesn't account for any change in tire height you have however.
dl
dl
Melting Slicks
Joined: Aug 2000
Posts: 2,310
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Re: How many teeth (Aaron76)
OK, here's their (Dave Emanuel's Tech Line from Corvette Fever June 2002) reply to someone who changed rear gears from 2.51:1 to 3.55:1 ...
"You can change the speedometer gearing by making a trip to your friendly nearby Chevrolet dealer. Keep in mind that tire diameter has an effect on overall gearing, so I can't tell you which gears you'lll need. However, if you have your calculator handy, you can get pretty close by working the following formulas.
If you don't have the tire-revs-per-mile data from the tire manufacturer, you can compute it as follows: tire revolution per mile equals 20168, divided by diameter in inches.
Once you have that number, the following formula will get you the tooth count needed: (number of drive teeth times axle ratio times tire revs per mile) divided by 1001 equals number of driven teeth.
With a 3.55 gear, you're probably going to need a 15 tooth drive gear and if you work the equations, you'll probably need a driven gear with 41, 42, 43, 44, or 45 teeth, depending on the tire size. The dealer should have a chart with tooth count and part number cross-referenced. In addition to the two gears, you may also need a sleeve and retainer (depending on the ones currently installed)."
Whew! I hope I typed all of that correctly.
The drive gear in is in the tranny in the tailshaft section. It can be metal or plastic. I don't think you'll be able to tell whether it's metal or plastic or how many teeth it has without removing the tailshaft. I replaced mine when I did my shift kit. You need to remove the driveshaft. The plastic ones are held by a clip. I think the metal ones are pressed on. They can be persuaded off with a wrench and hammer, but I had the plastic one fortunately, so I don't know how hard it is to get the metal ones off. Hopefully, you won't have to change the drive gear. The driven gear is pretty easy to get to on the TH350. You'll probably spill a little trans fluid changing the driven gear. You'd probably lose a lot if you pulled the tailshaft (I had already removed the pan an valve body so I very little came out of mine).
Anyway, I hope some of this helps and I hope your dealership can be a little more accurate than mine. They seemed to have a tough time figuring out exactly what (drive gear and driven gear) was supposed to be in my trans :crazy: But, there's a possibility my trans isn't the original; I've never been able to find numbers on it. I'd definitely try the driven gear route. The drive gear isn't a horrible job, but it's not a piece of cake either.
Jerry
[Modified by jerryp58, 5:17 PM 8/19/2002]
"You can change the speedometer gearing by making a trip to your friendly nearby Chevrolet dealer. Keep in mind that tire diameter has an effect on overall gearing, so I can't tell you which gears you'lll need. However, if you have your calculator handy, you can get pretty close by working the following formulas.
If you don't have the tire-revs-per-mile data from the tire manufacturer, you can compute it as follows: tire revolution per mile equals 20168, divided by diameter in inches.
Once you have that number, the following formula will get you the tooth count needed: (number of drive teeth times axle ratio times tire revs per mile) divided by 1001 equals number of driven teeth.
With a 3.55 gear, you're probably going to need a 15 tooth drive gear and if you work the equations, you'll probably need a driven gear with 41, 42, 43, 44, or 45 teeth, depending on the tire size. The dealer should have a chart with tooth count and part number cross-referenced. In addition to the two gears, you may also need a sleeve and retainer (depending on the ones currently installed)."
Whew! I hope I typed all of that correctly.
The drive gear in is in the tranny in the tailshaft section. It can be metal or plastic. I don't think you'll be able to tell whether it's metal or plastic or how many teeth it has without removing the tailshaft. I replaced mine when I did my shift kit. You need to remove the driveshaft. The plastic ones are held by a clip. I think the metal ones are pressed on. They can be persuaded off with a wrench and hammer, but I had the plastic one fortunately, so I don't know how hard it is to get the metal ones off. Hopefully, you won't have to change the drive gear. The driven gear is pretty easy to get to on the TH350. You'll probably spill a little trans fluid changing the driven gear. You'd probably lose a lot if you pulled the tailshaft (I had already removed the pan an valve body so I very little came out of mine).
Anyway, I hope some of this helps and I hope your dealership can be a little more accurate than mine. They seemed to have a tough time figuring out exactly what (drive gear and driven gear) was supposed to be in my trans :crazy: But, there's a possibility my trans isn't the original; I've never been able to find numbers on it. I'd definitely try the driven gear route. The drive gear isn't a horrible job, but it's not a piece of cake either.
Jerry
[Modified by jerryp58, 5:17 PM 8/19/2002]
