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Begin OCR Text:
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D E_ _ _ _ __ _ O _
The overdriue unit is of the ePicyclic tyPe and is E_E_TRl_A L SySTE M
attached to the rear end of the ge3rboK. lts design _he overdr._ve ._s engaged by e_eçtro-hydrau_._ç
and ConStruCtion are ShoWn in Fig. 4-34 and Il l UStra- means on the gearboK çouer there ._s a çontaçt
tion 4-C. The working pri nciple of the ouerdrive is wh._çh çuts ._n when qth speed ._g engaged _hus the
aS folloWS . overdr__ve çan on_y be engaged when th' __s gpeed
is engaged. It is switched on by means of a switch
Dl RE_T D RlvE po S_Tlo N placed underneath the steeri ng wheel. This switch
closes the ci rcuit via the switch on the gearboK to
When trauel ling fo_afd S power iS tranSmitted a so_eno__d on the overdr__ve. _he so_eno__d armature
from the gearboK mainShaft through the uni-di reC- __g thus moved and th__s operates the çontro_ ua_ue
tional clutch to the ouptut shaft of the overdrive. to the pog__t__on For overdr__ve
At the same ti me the clutch sliding member (posi- _
tion l, Fig . 4-27). is pressed by four springs against
the tapered part of the output shaft. When rever- R _ S ST
sing or when the engine acts as a brake, the torque HYD A U Ll Y EM
is transmitted through the clutch sliding member. __he hydrau Iic system consists of the following main
parts . Pre-filter, plu nger pump, fi ne filter, hydraulic
cylinders and plungers, relief valve and a control
OVE R D RIV E PO SITl O N va_ve wh_çh _g operated by the so_eno_d.
In the overdrive position the clutch sliding member The relief valve has a special construction with a
is pressed against the brake ring (see l l , Fig. 4-27) hydraulic piston and four different springs. lt has
with the help of the pistons (27, Fig. 4-34) i n the three different functions . It must maintain a low
hydraulic cylinders. This also locks the sunwheel. pressure in the system with di rect drive, a high
Since the planet gear retai ners are li nked to the pressure with overdrive, and also provide smooth
mainshaft through the spli nes, the planet gears are chang ing when shifti ng from overdrive to direct
forced to rotate arou nd the sunwheel . The output drive and vice versa. Its function is described in
shaft wi l l thus rotate at a higher speed than the more detai l below.
mainshaft. The oil flow with direct drive is shown in fig. 4-31 .
3
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I /
_
l _ _ _ _ /
_ Non-rotating Da_s _ _ 4 _
_ parts roiaing at a hIg_er speed ihan ihe inpui shari yg,_p
_ paris rDtating ai t_c samc speed as the inpui sha_t Fig. __z8. Eiect_icai c_rcuit d_agra_
) . Lead from fusebo_
2 Switch for overdrive
Flg_ h27. Wor_lng p_i_ciple ol oVe_dr_Ve 3 wa_____g _a_p _o_ ove_d___ve
l 0ireCt drive pos_tion O Switch on gearbo_
l l Overdrive poSition C_ SoIEnoid on Dverdr_ve
4 _. 1 7
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