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#1 |
Registered User
Join Date: Aug 2013
Location: San Diego, CA
Posts: 236
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$200+ to switch speedo in transmission swap
I had my T350 tranny swapped out to a 700R4. I have 4.10 gears and a 350 motor and my speedo is now showing about 90MPH when I'm cruising at about 70MPH. I ordered some new gear for the speedo but the tranny shop told me that they were the wrong gears and I had to get an in-line adapter. I called a local speedo shop and he told me it would be around $200ish to get the adapter nad fit it on the truck. This seems awefully expensive.
Anyone else deal with this issue?
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1973 Chevy K20 |
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#2 |
BAD BOW-Silverado XST
Join Date: May 2000
Location: Senior Member from Austin, TX
Posts: 6,431
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Re: $200+ to switch speedo in transmission swap
Go here: Scroll down to GM Ratio Adapter
http://www.transmissioncenter.org/70...List.htm#Gears |
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#3 |
Registered User
Join Date: Aug 2013
Location: San Diego, CA
Posts: 236
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Re: $200+ to switch speedo in transmission swap
That looks like it will work and the price is reasonable. Now I just need to call them to see which one I need.
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1973 Chevy K20 |
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#4 |
GM Addicted
Join Date: Jan 2009
Location: Visalia, Ca
Posts: 2,294
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Re: $200+ to switch speedo in transmission swap
You can swap the plastic gears for the speedo in the transmission it's what I did.
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![]() ![]() 73 GMC, 54 Caddy, 2010 Silverado, 68 C10 RIP DAd My 73 GMC Truck Build Pic 2010 Silverado 4/6 on 24s IG:MacsGarage |
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#5 |
Registered User
Join Date: Aug 2013
Location: San Diego, CA
Posts: 236
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Re: $200+ to switch speedo in transmission swap
I tried that and the shop that did my tranny said I ordered the wrong gears cause they are not on the tranny.
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1973 Chevy K20 |
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#6 |
Registered User
Join Date: Feb 2012
Location: Mud Lake, Idaho
Posts: 346
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Re: $200+ to switch speedo in transmission swap
I went on Bowtie Overdrive and they had a chart that you input your tire size, and axle ratio and it told you what gear you should have in the trans and what gear for the speedo drive out. Its easy to pull the tail housing and install or change the output shaft gear then match it with the right driven gear and your speedo should be pretty close.
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#7 |
Registered User
Join Date: Feb 2012
Location: St. Louis, MO
Posts: 80
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Re: $200+ to switch speedo in transmission swap
I've never done the swap, but a quick google/youtube search shows that 84chevyguyid is right. Here's a youtube video on how easy the gear swap is.
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Azulita - 84 Chevy Scottsdale Longbed 305/350 |
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#8 |
BAD BOW-Silverado XST
Join Date: May 2000
Location: Senior Member from Austin, TX
Posts: 6,431
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Re: $200+ to switch speedo in transmission swap
He has a 4X4. The speedo adaptor is in the engine bay. He can't swap gears down at the tailshaft.
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#9 |
Registered User
Join Date: Feb 2012
Location: St. Louis, MO
Posts: 80
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Re: $200+ to switch speedo in transmission swap
I totally ignored the 4x4 bit. Pay no attention to me.
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Azulita - 84 Chevy Scottsdale Longbed 305/350 |
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#10 |
Registered User
Join Date: Aug 2013
Location: San Diego, CA
Posts: 236
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Re: $200+ to switch speedo in transmission swap
Thats right....I forgot what he said exactly but thats is why the gears I ordered wont fit.
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1973 Chevy K20 |
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#11 |
Registered User
Join Date: Nov 2011
Location: 19
Posts: 607
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Re: $200+ to switch speedo in transmission swap
Or you could get one of these...
![]() Speedo gear ratio adapter http://www.gaugeguys.com/speedcorrect.htm
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1999 Chevy K2500 RCLB 350 4L80e 2004 Chevy 3500 C&C Dmax Allison |
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#12 | |
Registered User
![]() Join Date: Nov 2012
Location: Los Angeles, CA
Posts: 450
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Re: $200+ to switch speedo in transmission swap
Quote:
First - what transfer case to you have behind the 700r4? 203, 205, 208, 241? 700R4 is 27 spline output so I'm leaning towards 203, 208 or 241. The 700R4 to 205 requires fancy ($$$) adaptor. Anyway, not sure what yrs you are dealing with but that's where the change for speedo ratio is. It drives off the main shaft of the transfer case. You need to figure out what you got vs what you need. There is only a few color combos. Pull out the cable from the transfer case and look inside. It can only be one of four colors. Blue, gray, red or yellow. 15 to 19 teeth. Now look at the gear on the cable. Runs from 37 to 40 teeth then 41 to 45. All by color. Post up what color you have inside and on the cable and I can help figure what you need. You can use an adaptor for ease of install but couple of seals & $30 in gears vs $200 adaptor. You'll still need to look inside so you can get the right ratio. adaptor |
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#13 |
Registered User
Join Date: Apr 2012
Location: san diego ca
Posts: 618
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Re: $200+ to switch speedo in transmission swap
did you get the speed o working right ? mines 10 off i need to do it to.
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#14 |
Registered User
Join Date: Aug 2013
Location: San Diego, CA
Posts: 236
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Re: $200+ to switch speedo in transmission swap
I did buy the part and went to install it. It turns out there was already a speedo adapter in place and I just removed it and installed the stock cable. It now seems to run close to normal. I dont want to install the adapter that I bought because it is a reducer and will reduce it 27.5%.
I'm sort of upset at the shop cause they never mentioned that there was a speedo adapter already in place and unfortuantely I did not check before ordering the part.
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1973 Chevy K20 |
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#15 | |
Registered User
![]() Join Date: Oct 2010
Location: Town of Summit, WI
Posts: 322
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Re: $200+ to switch speedo in transmission swap
Quote:
the label on the transfer case says Model 208 C.
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2017 Silverado LTZ 6.2 1984 Scottsdale K10 - 468 700r 4x4 lwb 1978 GMC Sierra Grande K15 350 Soond to be 406 th350 4x4 swb 1968 GMC 20 305 V6 good ole wood hauler. ![]() Good Fences make good neighbors |
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#16 |
Registered User
![]() Join Date: Oct 2010
Location: Town of Summit, WI
Posts: 322
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Re: $200+ to switch speedo in transmission swap
Typeo in my privous post, my gears are 3.73
__________________
2017 Silverado LTZ 6.2 1984 Scottsdale K10 - 468 700r 4x4 lwb 1978 GMC Sierra Grande K15 350 Soond to be 406 th350 4x4 swb 1968 GMC 20 305 V6 good ole wood hauler. ![]() Good Fences make good neighbors |
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