88 Chevy Cheyenne 700R4 to TH350 Speedometer/Tachometer


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88 Chevy Cheyenne 700R4 to TH350 Speedometer/Tachometer Help

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Auto Repair Home>> Automotive Repair>> Automotive Wiring and Electrical

BMcKinley
New User

Sep 1, 2014, 7:14 PM

Post #1 of 3 (1943 views)

88 Chevy Cheyenne 700R4 to TH350 Speedometer/Tachometer Help	Sign In

I have an 88 chevy cheyenne. it has a 350 5.7 and the guys i bought it from replaced the 700r4 transmission to a turbo 350. it does not have a vss port on the th350 so the original speedometer and odometer do not work. im thinking about getting an aftermarket speedometer and just run the mechanical signal to it but i also want to install a tachometer. whats the best way to go about this whole process of getting a working speedometer, odometer, and tachometer while still keeping the turbo 350 tranny?

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 1, 2014, 11:17 PM

Post #2 of 3 (1926 views)

Re: 88 Chevy Cheyenne 700R4 to TH350 Speedometer/Tachometer Help	Sign In

! Why did you do that? 700R is/was a great trans and behaves exactly as a the TH350 if you want just shift to "3" or non "OD" on dash suggested for towing and conditions where you don't want torque converter to lock for so called 4th or overdrive.

Without the VSS you lose some features and possibly engine management functions. Not sure what to do but you should find out what you can or is impractical to do to have accurate speedometer and odometer. Tach another trick to tap wire to get the pulse for it.

700R was TMK around before using a VSS but your dash and that wiring about has to be all different.

Easiest and best is to put the OE trans back or swap out for one not knowing what you need this thing for it's still about 20 years too new to cobble up trans and a 350/5.7 to get all you want and accurate. I think if speedometer is cable you can get a mechanism to set it to the rear end ratio so it reads proper speed and miles. That or may need to change output shaft + housing?
If you really want this downgraded trans for some reason you may need to consult a transmission shop for options to keep it as I think it was an optional trans or base trans over the 700R for the year or was a few model years older but not certain for every application,

T

Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Sep 2, 2014, 4:30 AM

Post #3 of 3 (1920 views)

Re: 88 Chevy Cheyenne 700R4 to TH350 Speedometer/Tachometer Help	Sign In

I agree, save your money for a 700R4. You'll be much happier.

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