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190XT Tach With groundspeed

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=209564
Printed Date: 02 Jan 2026 at 1:13am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com


Topic: 190XT Tach With groundspeed
Posted By: MadCow
Subject: 190XT Tach With groundspeed
Date Posted: 01 Jan 2026 at 7:14pm
I really like having all the lines on the tachometer with ground speed based on gear. The D21 and D19 tachometers spin the same direction as the 190, and have these marks. Any idea which would have the closest gear ratios?

I don't have a parts/service for either D series to compare transmission specs.

190xt

Gear main counter ratio
1st 36T    13T    0.36
2nd 31T    18T    0.58
3rd 27T    23T    0.85
4th 19T    35T    1.84
Differential 9 to 35 or 3.88
Final drive 13 to 93 or 7.15

I can't figure out the ppower director but I think:

Gear drive driven ratio
Low    27    30    1.11
High   19    26    1.37

'gear' total ratio
1     11.09     
2     13.68
3     17.86
4     22.04
5     26.17
6     32.30
7     56.66
8     69.93


Hmmm. Math isn't adding up. I'm missing something somewhere. But this can start a conversation.



Replies:
Posted By: rw
Date Posted: 01 Jan 2026 at 7:32pm
I use an old radar planter monitor that has  ground speed spray, also the light bar I use has MPH. Both are old technology now, not real expensive, tire size and slippage are moot. The old Tachs with mph are cool and get you close. I find the more modern tools more accurate for mph especially spraying. 


Posted By: Les Kerf
Date Posted: 01 Jan 2026 at 7:42pm
Originally posted by rw rw wrote:

I use an old radar planter monitor that has  ground speed spray... 
When I was in the Marines I used to repair the doppler Ground Speed and Drift Angle radar unit that was used on the F4 Phantoms, they weren't much good under 100 Knots or so Wink


Posted By: MadCow
Date Posted: 01 Jan 2026 at 8:07pm
It's not the novelty than precision, really, for me.

I think old simple mechanical tech is better than electronics, and I like the sleak look.

It might be futile, because I might get a spray controller and radar anyway... But dang I like the look of the full tachs, and the simplicity.



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