700r4 Speedometer with 20's - The 1947 - Present Chevrolet & GMC Truck Message Board Network

5150 · 03-07-2006, 11:06 PM

Hey guys,

How can I get my speedometer on my new 700r4 to read correct with my 20's. I have a mechanical speedometer, so I'm not sure if I'm just going to be stuck without a speedometer or not.

cdowns · 03-07-2006, 11:11 PM

talk to a tranny shop they can either give you the right gear or you can also get an add on gear box to step up or down to correct it

5150 · 03-07-2006, 11:15 PM

I talked to the tranny shop and he didn't seem to know how. I figured somebody on here would have had this problem and fixed it.

**pjmoreland** · 03-07-2006, 11:22 PM

Does your transmission have an electric speedometer output right now? If so, you'll need to replace the speedometer output with a gear style. You'll need the drive gear that mounts to the transmission output shaft, the driven gear that the speedometer cable connects to, and the housing that holds the driven gear (three sizes available depending on the driven gear size).

http://www.73-87.com/7387garage/drivetrain/spdgears.htm

http://www.73-87.com/7387garage/drivetrain/speedo.htm

http://www.tciauto.com/tech_info/speedo_gears.htm

**pjmoreland** · 03-07-2006, 11:35 PM

What size are your rear tires? What rear end gears do you have?

5150 · 03-08-2006, 03:01 PM

I have the mechanical speedometer

Also my rear tires are 275/45/20 with 4.11 gears

Musclerodz · 03-08-2006, 03:45 PM

Factory or aftermarket guage? I know Autometer sells different ratio drives for their mech speedos.

Mike

**pjmoreland** · 03-08-2006, 04:00 PM

The TCI website indicates that your tire diameter is 29.74". TCI also indicates that with a 15-tooth driving gear, you'd need a 41.765 driven gear, so A 15-tooth (gray) driving gear and a 42-tooth (green) driven gear is the closest you'll get. You'll also need the driven gear housing for 40-45 tooth gears if you don't already have that one.

Here are the GM part numbers:

15-tooth (gray) driving gear = 8642620 (TCI 880018)
42-tooth (green) driven gear = 1362049 (TCI 880030)
40-45 Housing = 25512339 (TCI 880023)

If your housing has 40 41 42 43 on the side of it, then it should work fine.

5150 · 03-08-2006, 04:30 PM

I'm going to go pic up the tranny on tomorrow. I'll probably understand a little more when I see it. Tranny's aren't my thing. I the kind of guy that needs to be looking at it or have pics.

It looks like it's going to be around $40 for the three gears.

Tx Firefighter · 03-08-2006, 08:35 PM

Quote:

Originally Posted by yellow69

It looks like it's going to be around $40 for the three gears.

It's just two gears.

As long as you have the proper housing for your gears, price is cheap. The housing is a little over 20 bucks if I remember correctly. Yours will be labeled as to which gears it's for.

5150 · 04-07-2006, 12:44 PM

Okay, here's what I pulled out of the tranny.

Which one needs to be replaced?

Also this spring came out also, I can't figure out where it came from or if it was accidentally in there. GO FIGURE!!

cwilli84 · 04-07-2006, 01:10 PM

I believe he stated that both the gears need replacing in order to get the correct reading fro your gauge. Spring ??????

5150 · 04-08-2006, 11:59 AM

Just wanting to make sure these are the right ones:

http://www.powerandperformancenews.c...Category_Code=

http://www.powerandperformancenews.c...Category_Code=

03-07-2006, 11:06 PM	#1
5150 C10 Club Tennessee Join Date: Mar 2003 Location: White House, TN 37188 Posts: 8,281	700r4 Speedometer with 20's Hey guys, How can I get my speedometer on my new 700r4 to read correct with my 20's. I have a mechanical speedometer, so I'm not sure if I'm just going to be stuck without a speedometer or not. __________________ Bryan www.gmtruckshow.com Project "Andes"-Halen's First Truck Project: Patina Burb for he is God’s servant for your good. But if you do wrong, be afraid, for he does not bear the sword in vain. For he is the servant of God, an avenger who carries out God’s wrath on the wrongdoer. Romans 13:4

03-07-2006, 11:11 PM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: 700r4 Speedometer with 20's talk to a tranny shop they can either give you the right gear or you can also get an add on gear box to step up or down to correct it __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

03-07-2006, 11:15 PM	#3
5150 C10 Club Tennessee Join Date: Mar 2003 Location: White House, TN 37188 Posts: 8,281	Re: 700r4 Speedometer with 20's I talked to the tranny shop and he didn't seem to know how. I figured somebody on here would have had this problem and fixed it. __________________ Bryan www.gmtruckshow.com Project "Andes"-Halen's First Truck Project: Patina Burb for he is God’s servant for your good. But if you do wrong, be afraid, for he does not bear the sword in vain. For he is the servant of God, an avenger who carries out God’s wrath on the wrongdoer. Romans 13:4

03-07-2006, 11:22 PM	#4
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,240	Re: 700r4 Speedometer with 20's Does your transmission have an electric speedometer output right now? If so, you'll need to replace the speedometer output with a gear style. You'll need the drive gear that mounts to the transmission output shaft, the driven gear that the speedometer cable connects to, and the housing that holds the driven gear (three sizes available depending on the driven gear size). http://www.73-87.com/7387garage/drivetrain/spdgears.htm http://www.73-87.com/7387garage/drivetrain/speedo.htm http://www.tciauto.com/tech_info/speedo_gears.htm Last edited by pjmoreland; 03-07-2006 at 11:24 PM.

03-07-2006, 11:35 PM	#5
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,240	Re: 700r4 Speedometer with 20's What size are your rear tires? What rear end gears do you have?

03-08-2006, 03:01 PM	#6
5150 C10 Club Tennessee Join Date: Mar 2003 Location: White House, TN 37188 Posts: 8,281	Re: 700r4 Speedometer with 20's I have the mechanical speedometer Also my rear tires are 275/45/20 with 4.11 gears __________________ Bryan www.gmtruckshow.com Project "Andes"-Halen's First Truck Project: Patina Burb for he is God’s servant for your good. But if you do wrong, be afraid, for he does not bear the sword in vain. For he is the servant of God, an avenger who carries out God’s wrath on the wrongdoer. Romans 13:4

03-08-2006, 03:45 PM	#7
Musclerodz Senior Member Join Date: Aug 2005 Location: OKC, OK Posts: 2,364	Re: 700r4 Speedometer with 20's Factory or aftermarket guage? I know Autometer sells different ratio drives for their mech speedos. Mike __________________ Mike Redpath

03-08-2006, 04:00 PM	#8
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 6,240	Re: 700r4 Speedometer with 20's The TCI website indicates that your tire diameter is 29.74". TCI also indicates that with a 15-tooth driving gear, you'd need a 41.765 driven gear, so A 15-tooth (gray) driving gear and a 42-tooth (green) driven gear is the closest you'll get. You'll also need the driven gear housing for 40-45 tooth gears if you don't already have that one. Here are the GM part numbers: 15-tooth (gray) driving gear = 8642620 (TCI 880018) 42-tooth (green) driven gear = 1362049 (TCI 880030) 40-45 Housing = 25512339 (TCI 880023) If your housing has 40 41 42 43 on the side of it, then it should work fine. Last edited by pjmoreland; 03-08-2006 at 04:02 PM.

03-08-2006, 04:30 PM	#9
5150 C10 Club Tennessee Join Date: Mar 2003 Location: White House, TN 37188 Posts: 8,281	Re: 700r4 Speedometer with 20's I'm going to go pic up the tranny on tomorrow. I'll probably understand a little more when I see it. Tranny's aren't my thing. I the kind of guy that needs to be looking at it or have pics. It looks like it's going to be around $40 for the three gears. __________________ Bryan www.gmtruckshow.com Project "Andes"-Halen's First Truck Project: Patina Burb for he is God’s servant for your good. But if you do wrong, be afraid, for he does not bear the sword in vain. For he is the servant of God, an avenger who carries out God’s wrath on the wrongdoer. Romans 13:4 Last edited by 5150; 03-08-2006 at 04:32 PM.

04-07-2006, 12:44 PM	#11
5150 C10 Club Tennessee Join Date: Mar 2003 Location: White House, TN 37188 Posts: 8,281	Re: 700r4 Speedometer with 20's Okay, here's what I pulled out of the tranny. Which one needs to be replaced? Also this spring came out also, I can't figure out where it came from or if it was accidentally in there. GO FIGURE!! Attached Images __________________ Bryan www.gmtruckshow.com Project "Andes"-Halen's First Truck Project: Patina Burb for he is God’s servant for your good. But if you do wrong, be afraid, for he does not bear the sword in vain. For he is the servant of God, an avenger who carries out God’s wrath on the wrongdoer. Romans 13:4

04-07-2006, 01:10 PM	#12
cwilli84 1FINE69 Join Date: Aug 2003 Location: Detroit, Michigan Posts: 239	Re: 700r4 Speedometer with 20's I believe he stated that both the gears need replacing in order to get the correct reading fro your gauge. Spring ?????? __________________ Had a 69 swb fleetside 350zz3 w 400turbo trans oak lined bed with rhino coated sides red exterior. SOLD

04-08-2006, 11:59 AM	#13
5150 C10 Club Tennessee Join Date: Mar 2003 Location: White House, TN 37188 Posts: 8,281	Re: 700r4 Speedometer with 20's Just wanting to make sure these are the right ones: http://www.powerandperformancenews.c...Category_Code= http://www.powerandperformancenews.c...Category_Code= __________________ Bryan www.gmtruckshow.com Project "Andes"-Halen's First Truck Project: Patina Burb for he is God’s servant for your good. But if you do wrong, be afraid, for he does not bear the sword in vain. For he is the servant of God, an avenger who carries out God’s wrath on the wrongdoer. Romans 13:4

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