Interpretation ID: nht72-1.1

DATE: 12/11/72

FROM: AUTHOR UNAVAILABLE; E. T. Driver; NHTSA

TO: Chrysler United Kingdom Ltd.

TITLE: FMVSS INTERPRETATION

TEXT: This is in reply to your letter of November 7, 1972, about Federal Motor Vehicle Safety Standard No. 102 as applied to a four speed automatic gear box.

As described, gear transmission functions as follows:

"When the gear selector is in any forward position and the vehicle speed falls the automatic Mechanism will cause the drive ratio to eventually fall to the lowest gear and thereafter to disengage at about 6 mph leaving the vehicle in a state of 'free-wheel'."

Paragraph S3.1.2, Transmission Braking Effect, requires that:

"In vehicles having more than one forward transmission gear ratio, one forward drive position shall provide a greater degree of engine braking than the highest speed transmission ratio at vehicle speeds below 25 miles per hour."

Your transmission, as described, does not meet this requirement, since, in downshifting, the drive ratio would disengage at about 6 miles per hour leaving the vehicle in a state of "free-wheel" with no engine braking at all.

Sincerely,

CHRYSLER UNITED KINGDOM LTD

The Office of Standards Motor Vehicle Safety Performance Service, U.S. Department of Transportation, Federal Highway Administration, National Highway Safety Bureau,

NOVEMBER 7, 1972

Dear Sirs,

Interpretation of F.M.V.S.S. 102.

We are considering the use of a four speed Automatic Gear Box which has the following characteristic:

When the gear selector is in any forward position and the vehicle speed falls the automatic mechanism will cause the drive ratio to eventually fall to the lowest gear and thereafter to disengage at about 6 mph leaving the vehicle in a state of "free-wheel".

We notice F.M.V.S.S. requires an automatic gear box to be such that: "One forward drive position shall provide a greater degree of engine braking than the highest speed transmission ratio".

Whilst this clause would be met with the characteristic described at speeds above 6 mph it could not be considered to be met at speed below 6 mph.

I would be grateful if you would let me know whether or not you consider such a gear box would meet the requirements of F.M.V.S.S. 102.

P.J.P Horris. Manager, Vehicle Legislation.