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#1 |
Registered User
Join Date: Jan 2012
Location: Gulf Breeze florida
Posts: 26
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700R4 To TH350, speedometer off... also tick/knock sound
So I had a turbo 350 swap done on my truck. I love it. Although I miss the one gear, no more worries of the TV cable. Anyhow, when I noticed that I have to drive the truck at 55mph to get it to go 45 mph. I'm under the impression I can just swap the speedo gear in the trans, however I have no idea what gear to go to.
No idea what the stock rear end in my truck is. Truck: 1986 GMC 1500 single cab LWB 5.7L 4 Bolt Main V8 Any advice or help would be greatly appreciated. Also recently noticed a ticking or knocking from under the truck. Truck has always been maintained well. Seems to have happened just after the trans swap. I dont think its the bottom end of the motor... Sounds more like the torque converter or flywheel. To be honest IM curious is anyone else has had this happen. I know the sound is typically a bad bearing in the bottom end. However like I said really sounds to be more on the tranny side. |
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#2 | |
Registered User
Join Date: Sep 2012
Location: Broken Arrow, ok
Posts: 181
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Re: 700R4 To TH350, speedometer off... also tick/knock sound
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#3 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,602
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Re: 700R4 To TH350, speedometer off... also tick/knock sound
Lots of info in here.
http://www.transmissioncenter.net/sp...____va.htm#350 |
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#4 | |
Registered User
Join Date: Sep 2012
Location: Broken Arrow, ok
Posts: 181
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Re: 700R4 To TH350, speedometer off... also tick/knock sound
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#5 |
Registered User
Join Date: May 2012
Location: Colo Springs, CO
Posts: 870
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Re: 700R4 To TH350, speedometer off... also tick/knock sound
I'm not familiar with the 350 but if the speedo connections are the same:
I'd first start with lubing your speedo cable. There is a lube out there but you will need to pull out your instrument cluster and speedo gauge to get access to lubing it. Once the speedo is removed, the cable will pull out of the sleeve. When you feed it back in, lube it as you go. Check your speedo cable for any kinks or large bends. It is possible that the drive or driven gears within the t-case got damages or are worn. One of the gears is pretty easy to change out but the other one requires pulling the tailshaft off of the Tcase. Basically, in my 89' I had the speedo jumping around. I tried a new cable, tried lubing it, tried swapping one of the gears (the easier on) with no success. Even my cruise control couldn't hold steady because of the jumping around. I finally went "all in" and converted my cable speedo to a electronic one. Took a LOT of work but really turned out great! Rock solid speedo, cruise rock solid and 6 digit odometer.
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- Jeff 89' K5 Blazer, 2.5" lift, 35" tires ![]() 04' GMC Yukon XL, 3/4 ton, 8.1L |
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#6 |
Registered User
Join Date: Jul 2011
Location: SW Ontario
Posts: 1,204
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Re: 700R4 To TH350, speedometer off... also tick/knock sound
Actually you do need to change the gears for the swap unless you get a drive and driven gear from a same axle ratio vehicle. The 700r4 uses a large diameter driven gear, the th350 uses the small diameter driven gear, if you use the th350 speedo adaptor from a junkyard source [and the drive gear from the 700r4], your speedo will more than likely read fast. Mine was exactly 2x actual speed. I had to watch out that I didn't destroy my speedo on the shakedown run.
Do you know how many teeth your driven and drive gear have? Then we can work out what combination to get you close. Actual speed verified with a GPS or roadside radar unit? Or other confirmed CORRECT speedo when following somebody with specific instructions to drive at exactly 60mph? =-) Alex. |
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#7 |
Registered User
Join Date: Dec 2011
Location: Arlington WA
Posts: 1,728
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Re: 700R4 To TH350, speedometer off... also tick/knock sound
if oyu left the engine in while swapping transmissions the distibutor may have hit the fire wall. that can cause the cap to sit crooked and knock. a cracked flex plat can make noise too
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GMC C15 355 SM465 3.73 80 C10 cruiser build thread 79 short stepside crew cab. big and ugly. build thread |
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#8 | |
Registered User
Join Date: Nov 2011
Location: 19
Posts: 607
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Re: 700R4 To TH350, speedometer off... also tick/knock sound
Quote:
I put a 700r4 in place of a th350 and the th350 had a 10 tooth drive gear and a 19 tooth driven gear, the rear end has a 2:56 ratio and a 305 motor. Not sure how to figure out which gears to use for the 700r4, it was out of 89 pickup so it had a electric speedo. Thanks
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1999 Chevy K2500 RCLB 350 4L80e 2004 Chevy 3500 C&C Dmax Allison |
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#9 | |
Registered User
Join Date: Jul 2012
Location: Des Moines IA
Posts: 1,250
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Re: 700R4 To TH350, speedometer off... also tick/knock sound
Quote:
EDIT: Saved and uploaded their calculation for future just in case they every change their site.
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- 1981 Sierra 454, NV4500 swap - 2006 Z06, 25k miles - 1973 Nova - Project CarNova Virus on Youtube Last edited by bnoon; 11-23-2012 at 10:59 AM. |
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