Tach Seems high. Or am I? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Piper71c10 · 12-11-2003, 05:38 AM

when Driving down the road with 33" tires and 3.73 gears, I'm reading about 4.5k on the Tach.
:edit: I guess I am high. I meant to say that I'm doing 60mph on the speedo.

If I stab it, it goes over 5k.

anybody care to guess if this is right or wrong?

I've got a sunpro on the shelf I could hook up, but I'm lazy and ya'll know so much.

Piper!

Longhorn Man · 12-11-2003, 08:13 AM

Seems a bit high.

shuttermutt · 12-11-2003, 10:29 AM

Yeah, something's wrong. With that setup you should be cruising along at about 2,500 RPM tops. Automatic tranny? Are you sure you're making the 3rd gear shift?

Nova_Cobra64 · 12-11-2003, 10:40 AM

My friends car has that problem......TH350, 24" tires and a 2.70 rear end......turns about 3600 RPM to do 65 and has a top end around 110 MPH. I figure he should be doing about 2200 RPM at 65, and should be capable of doing 150 MPH with the 2.70 gears. He thinks the tach may be out, but it doesn't sound like it. Why else would be be hitting the light side of seven grand in under 3 seconds off the line, yet only running high 14's, low 15's (in a v8 vega).

Paul72 · 12-11-2003, 11:58 AM

Sorry, guys, the engineer in me just had to come out. This is like one of those word problems in math class!

From what I figure, you should be turning about 2280 RPM - assuming a 1:1 3rd gear. Sometimes a 33" tire is a little smaller than 33" (My 31's are actually a hair over 30"), but even at 32" it should still be about 2350 RPM.

Sounds like you're off by a factor of 2. Have you got the switch on the tach set to 8 cyl?

BtnkBndt · 12-11-2003, 12:32 PM

Trans slipping??

junkyardjohn · 12-11-2003, 12:38 PM

HI PIPER .... SOUNDS LIKE YOUR TACH IS FUBAR. I RUN ABOUT 2400 RPMs AT 60 MPH IN MY BLAZER WITH 32s. HOWS WASHINGTON?? SETTLED IN OK??? DROP ME A LINE WHEN YOU GET TIME. JOHN

Oborny71 · 12-11-2003, 01:01 PM

like paul72 said, ifs an aftermarket tach, make sure its set to 8cyl. mode, not 6 or 4. this will make it read higher

Burnsman · 12-11-2003, 01:17 PM

In regards to the v8 vega, if he is using the stock torque converter (they were dinky), the torque converter doesn't lock up until it reaches a fairly high rpm. The torque converter could be toast too.

Piper71c10 · 12-11-2003, 03:37 PM

It's a stock tach, tho I can't tell if it's for the 8cyl or 6cyl. It's not stamped anywhere on it.

The Trans is making the shift. I know that's fine. I guess I'll hook up that other tach today and see what happens. Any reccomendations on fixing my factory tach?

Thanks guys!

Alex Hayley · 12-11-2003, 03:45 PM

There should be a hole in the back of the tach with an adjustment screw in it. Using an additional tach, you can set the stock tach by turning the screw until the two tachs match.

68 Suburban · 12-11-2003, 05:47 PM

Piper71c10,
Love the travel trailer!!! What year and model?

Here are pictures of one I had before I sold it to get my Avion Travel Trailer.

http://members.cox.net/topherc/tt/1.htm

Piper71c10 · 12-11-2003, 05:54 PM

68 burb -- It's a 1950 Sportsman "Aloja" by Modernistic industries. 12' model.

A bigger pic : http://67-72chevytrucks.com/vboard/s...threadid=72079

Caught the edge of one side with the Uhaul on the drive up here and kindof crunched it. Looks like I'm expanding my bodyworking skills this summer.

Piper

68 Suburban · 12-11-2003, 05:58 PM

That is a Sweet Trailer! This is what I got rid of my Lakewood for. I still miss that little lakewood

More Pics Here:
http://members.cox.net/topherc/avion/1.htm

Sorry to highjack your thread, but I love these old trailers

Piper71c10 · 12-11-2003, 06:06 PM

Burb- No worries. I really dig these trailers too. I think they are coming back in a major way as well. It seems like I see them on TV more and more everyday.

Dug that Black and white tile in the lakewood. Did you do that yourself?

Piper

68 Suburban · 12-11-2003, 06:11 PM

Quote:

Originally posted by Piper71c10
Burb- No worries. I really dig these trailers too. I think they are coming back in a major way as well. It seems like I see them on TV more and more everyday.

Dug that Black and white tile in the lakewood. Did you do that yourself?

Piper

Yeah, that lakewood turned out real cool. Nice and homey. I bought it for $500 here in Phx. A friend did the curtains for me. I wanted a nautical theme. The materials cost less than $100 for the curtains. I bought the tile at Lowes and did the checkerboard pattern. I think that was less than $50. I took the range top and had it powder coated black for $15, so it would match the Ice box. Everything else was in decent shape.

You are right about these trailer. I keep getting offered more and more for my Avion. They are only going to go up in value, so if you don't need the money or the space, hold on to it.

68 Suburban · 12-11-2003, 06:14 PM

I don't know if you have been to this site, but it is pretty good.

http://www.vintage-vacations.com/trailerlinks.htm

kiley · 12-12-2003, 03:30 AM

My 72 cst blazer has a factory tach. I always felt like it was running a little high. When I switched to hei i bought a new tach and strapped it to the column. The old tach was running about 500-600 higher than it should at 60 mph.

Piper71c10 · 12-25-2003, 08:06 PM

So, I pulled the dash to adjust the factory tach, and match it with another I've got laying around.

The factory tach is dead on at idle. Even revving it in park, it's still accurate. Only when I'm doing 60 on the highway is it off. Anyone help on this one?

I S'pose you are going to tell me I need a new factory tach. ...

Piper
Merry Christmas everyone!

Piper71c10 · 12-26-2003, 04:52 PM

ttt, anyone?

Steven Sellers · 12-26-2003, 05:17 PM

Without having one I cannot take it a part and see if they had an adjustment or what kind of mechanism its running in there. If it is essentially mechanical inside then there may just be a part you can change out, Im sure other year models probally used the same internals.
Does anyone have a junk one they can take apart and take a pic of the innards?
Some tachs are like gauges where they run a sector and gear as their movement and sometimes a tooth goes bad on these.
If I had a factory tach that works like you do I probally wouldnt take it a part and I have worked on thousands of tachs and such, without a lot of replacements I just wouldnt want to take a chance and I would live with it

Steve

Longhorn Man · 12-28-2003, 03:40 AM

The way I look at this, is the stock tachs were never too acurate when they were new...let alone 30+ years later.
If you want a tach to look neat and to have another option...get a stock one.
If you rip the truck through the gears, get a good aftermarket one.
Even an Auto Zone one would be more acurate.

magoo72 · 12-28-2003, 03:49 AM

thats why i went to a 3.08 gear,on the interstate i be turning bout 4 grand!with my 3.73's
but.........i may be high too,yanno to many ''burn outs"

Piper71c10 · 12-28-2003, 06:44 PM

Ya know, It's a little circuit board on the back of the Tach. I guess i'll dump the whole cluster on ebay.

Who knows. I don't really need the tach, but it's nice to have.

Thanks for the replies.

Piper!

12-11-2003, 05:38 AM	#1
Piper71c10 Unending Project Join Date: Aug 2003 Location: Sequim, WA Posts: 337	Tach Seems high. Or am I? when Driving down the road with 33" tires and 3.73 gears, I'm reading about 4.5k on the Tach. :edit: I guess I am high. I meant to say that I'm doing 60mph on the speedo. If I stab it, it goes over 5k. anybody care to guess if this is right or wrong? I've got a sunpro on the shelf I could hook up, but I'm lazy and ya'll know so much. Piper!

12-11-2003, 10:29 AM	#3
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	Yeah, something's wrong. With that setup you should be cruising along at about 2,500 RPM tops. Automatic tranny? Are you sure you're making the 3rd gear shift? __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

12-11-2003, 10:40 AM	#4
Nova_Cobra64 Registered User Join Date: Aug 2002 Location: Melville, SK Posts: 1,145	My friends car has that problem......TH350, 24" tires and a 2.70 rear end......turns about 3600 RPM to do 65 and has a top end around 110 MPH. I figure he should be doing about 2200 RPM at 65, and should be capable of doing 150 MPH with the 2.70 gears. He thinks the tach may be out, but it doesn't sound like it. Why else would be be hitting the light side of seven grand in under 3 seconds off the line, yet only running high 14's, low 15's (in a v8 vega). __________________ 2004 Silverado - Beater 1969 GMC - In progress http://67-72chevytrucks.com/vboard/s...d.php?t=441683 2011 Aveo - Work commuter 2013 Crestliner Fish Hawk 1650 - The reason no work gets done on the project truck.

12-11-2003, 11:58 AM	#5
Paul72 Registered User Join Date: Sep 2003 Location: Waterloo, IA Posts: 1,147	Sorry, guys, the engineer in me just had to come out. This is like one of those word problems in math class! From what I figure, you should be turning about 2280 RPM - assuming a 1:1 3rd gear. Sometimes a 33" tire is a little smaller than 33" (My 31's are actually a hair over 30"), but even at 32" it should still be about 2350 RPM. Sounds like you're off by a factor of 2. Have you got the switch on the tach set to 8 cyl? __________________ '72 Chevy K20 - 383/4sp/205 - SOLD after 41 years in the family Next project - K/5 Tahoe (71 Blazer on 99 Tahoe chassis) Build thread: http://67-72chevytrucks.com/vboard/s...d.php?t=789958

12-11-2003, 12:32 PM	#6
BtnkBndt Pennyless Fool Join Date: Oct 2003 Location: Forney,Tx Posts: 439	Trans slipping?? __________________ "Who owns this car with the peace sign, the mag wheels, and four on the floor?" 67 Short Step 283/TH400/4.11

12-11-2003, 08:13 AM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Seems a bit high.

12-11-2003, 12:38 PM	#7
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,427	HI PIPER .... SOUNDS LIKE YOUR TACH IS FUBAR. I RUN ABOUT 2400 RPMs AT 60 MPH IN MY BLAZER WITH 32s. HOWS WASHINGTON?? SETTLED IN OK??? DROP ME A LINE WHEN YOU GET TIME. JOHN __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST

12-11-2003, 01:01 PM	#8
Oborny71 Registered User Join Date: Apr 2001 Location: Lincoln, Nebraska Posts: 587	like paul72 said, ifs an aftermarket tach, make sure its set to 8cyl. mode, not 6 or 4. this will make it read higher __________________ 67 Chevy SWB - goal of a 1,000 hp weekend cruiser

12-11-2003, 01:17 PM	#9
Burnsman Chevy Freak Join Date: Sep 2002 Location: Meadville, Pa. Posts: 2,804	tach In regards to the v8 vega, if he is using the stock torque converter (they were dinky), the torque converter doesn't lock up until it reaches a fairly high rpm. The torque converter could be toast too. __________________ 69 GMC SWB, 350 70 Chevy LWB, 350 55 chevy gasser, 461 73 Camaro, 496 67 RS Camaro, 406 64 Chevelle, 588 71 Nova, 565 67 Camaro, 461

12-11-2003, 03:37 PM	#10
Piper71c10 Unending Project Join Date: Aug 2003 Location: Sequim, WA Posts: 337	It's a stock tach, tho I can't tell if it's for the 8cyl or 6cyl. It's not stamped anywhere on it. The Trans is making the shift. I know that's fine. I guess I'll hook up that other tach today and see what happens. Any reccomendations on fixing my factory tach? Thanks guys!

12-11-2003, 03:45 PM	#11
Alex Hayley Registered User Join Date: Jul 2000 Location: NC Posts: 987	There should be a hole in the back of the tach with an adjustment screw in it. Using an additional tach, you can set the stock tach by turning the screw until the two tachs match.

12-11-2003, 05:47 PM	#12
68 Suburban Registered User Join Date: Oct 2000 Location: From Chicago, Live in Phoenix, AZ Posts: 6,802	Piper71c10, Love the travel trailer!!! What year and model? Here are pictures of one I had before I sold it to get my Avion Travel Trailer. http://members.cox.net/topherc/tt/1.htm Last edited by 68 Suburban; 12-11-2003 at 05:52 PM.

12-11-2003, 05:54 PM	#13
Piper71c10 Unending Project Join Date: Aug 2003 Location: Sequim, WA Posts: 337	68 burb -- It's a 1950 Sportsman "Aloja" by Modernistic industries. 12' model. A bigger pic : http://67-72chevytrucks.com/vboard/s...threadid=72079 Caught the edge of one side with the Uhaul on the drive up here and kindof crunched it. Looks like I'm expanding my bodyworking skills this summer. Piper

12-11-2003, 05:58 PM	#14
68 Suburban Registered User Join Date: Oct 2000 Location: From Chicago, Live in Phoenix, AZ Posts: 6,802	That is a Sweet Trailer! This is what I got rid of my Lakewood for. I still miss that little lakewood More Pics Here: http://members.cox.net/topherc/avion/1.htm Sorry to highjack your thread, but I love these old trailers

12-11-2003, 06:06 PM	#15
Piper71c10 Unending Project Join Date: Aug 2003 Location: Sequim, WA Posts: 337	Burb- No worries. I really dig these trailers too. I think they are coming back in a major way as well. It seems like I see them on TV more and more everyday. Dug that Black and white tile in the lakewood. Did you do that yourself? Piper



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12-11-2003, 06:14 PM	#17
68 Suburban Registered User Join Date: Oct 2000 Location: From Chicago, Live in Phoenix, AZ Posts: 6,802	I don't know if you have been to this site, but it is pretty good. http://www.vintage-vacations.com/trailerlinks.htm

12-12-2003, 03:30 AM	#18
kiley Registered User Join Date: May 2003 Location: Keizer, OR Posts: 103	stock tach My 72 cst blazer has a factory tach. I always felt like it was running a little high. When I switched to hei i bought a new tach and strapped it to the column. The old tach was running about 500-600 higher than it should at 60 mph.

12-25-2003, 08:06 PM	#19
Piper71c10 Unending Project Join Date: Aug 2003 Location: Sequim, WA Posts: 337	So, I pulled the dash to adjust the factory tach, and match it with another I've got laying around. The factory tach is dead on at idle. Even revving it in park, it's still accurate. Only when I'm doing 60 on the highway is it off. Anyone help on this one? I S'pose you are going to tell me I need a new factory tach. ... Piper Merry Christmas everyone!

12-26-2003, 04:52 PM	#20
Piper71c10 Unending Project Join Date: Aug 2003 Location: Sequim, WA Posts: 337	ttt, anyone?

12-26-2003, 05:17 PM	#21
Steven Sellers Registered User Join Date: Jan 2002 Location: North Carolina Posts: 692	Without having one I cannot take it a part and see if they had an adjustment or what kind of mechanism its running in there. If it is essentially mechanical inside then there may just be a part you can change out, Im sure other year models probally used the same internals. Does anyone have a junk one they can take apart and take a pic of the innards? Some tachs are like gauges where they run a sector and gear as their movement and sometimes a tooth goes bad on these. If I had a factory tach that works like you do I probally wouldnt take it a part and I have worked on thousands of tachs and such, without a lot of replacements I just wouldnt want to take a chance and I would live with it Steve __________________ 2008 Buick Enclave(wifes new non wrecked) 1996 Jeep Cherokee 2002 2500HD 6.0L (traded) 1998 Jeep Grand Cherokee(wifes/wrecked) 1977 DJ5 postal jeep(mmm lots of fun) 1988 Toyota 2wd p/u(DD, blewup 199,000) 1991 Toyota 2ed p/u (sry just cant break these things) 1997 XR70 Honda 1991 Z50(FOR SALE) 1972 Z50 Honda 1970 SWB 350/knucklebuster "The adventure begins and I am confident that there will be no end".

12-28-2003, 03:40 AM	#22
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	The way I look at this, is the stock tachs were never too acurate when they were new...let alone 30+ years later. If you want a tach to look neat and to have another option...get a stock one. If you rip the truck through the gears, get a good aftermarket one. Even an Auto Zone one would be more acurate.

12-28-2003, 03:49 AM	#23
magoo72 Registered User Join Date: Jan 2003 Location: minden la Posts: 114	thats why i went to a 3.08 gear,on the interstate i be turning bout 4 grand!with my 3.73's but.........i may be high too,yanno to many ''burn outs"

12-28-2003, 06:44 PM	#24
Piper71c10 Unending Project Join Date: Aug 2003 Location: Sequim, WA Posts: 337	Ya know, It's a little circuit board on the back of the Tach. I guess i'll dump the whole cluster on ebay. Who knows. I don't really need the tach, but it's nice to have. Thanks for the replies. Piper!

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