HD785-7 POWER TRAIN 1-2 : Torque Converter

Compatible Unit Serial Number : 7001 and up 

STRUCTURE, FUNCTION
AND MAINTENANCE STANDART

for

POWER TRAIN (Part 1.2)

Torque Converter

A: Main oil pressure pickup port

B: Torque converter oil inlet port

C: Torque converter inlet oil pressure pickup port

D: Torque converter oil outlet port

E: To transmission control valve

F: To lockup clutch

G: Torque converter outlet oil pressure pickup port

H: To transmission lubrication circuit

J: Main flow rate selector valve inlet pressure pickup port

1. PTO gear (Number of teeth: 108)

2. PTO gear (Number of teeth: 91)

3. Brake cooling pump mounting port

4. Steering, hoist and hoist control pump mounting port

5. Torque converter, transmission charge, brake cooling, transmission lubrication and brake control pump mounting port

6. Torque converter valve

7. Torque converter outlet oil temperature sensor

Specifications

Type: 3-element, 1-stage, 2-phase with modulation and lockup clutch

Lockup clutch: Wet type multiple disc clutch hydraulic pressure control (with modulation valve)

Stall torque ratio: 1.99

1. Coupling

2. Input shaft (Number of teeth: 96)

3. Case

4. Drive case

5. Boss

6. Turbine

7. Outer race

8. Pump

9. Retainer

10. Stator shaft

11. Stator bushing

12. Free wheel

13. Stator

14. Lockup clutch disc

15. Lockup clutch piston

16. Lockup clutch housing

17. Retainer

No	Check Item		Criteria (unit: mm)						Remedy
1	Outside diameter of coupling oil seal contact surface		Standard size		Tolerance		Repair limit		Replace
			125		.0.1 -0.1		124.8
2	Inside diameter of input shaft seal ring contact surface		115		+0.035 +0.035		115.5
3	Clearance between clutch housing and piston (outside)		Standard size	Tolerance			Standart clearance	Clearance limit
				Shaft		Hole
			420	-0.5 -0.7		+0.097 +0.097	0.500 - 0.797	0.88
4	Clearance between clutch housing and piston (inside)		245	-0.100 -0.172		+0.072 +0.072	0.110 - 0.242	0.27
5	Inside diameter of retainer seal ring contact surface		190		+0.046 +0.046		190.5
6	Inside diameter of stator shaft seal ring contact surface		90		+0.035 +0.035		90.1
7	Wear of stator shaft seal ring	Width	5.95		-0.1 -0.1		5.45
		Thickness	6.5		±0.1		6.2
8	Inside diameter of free wheel transmission surface of outer race		140.53		±0.013		140.56
9	Outside diameter of stator shaft free wheel transmission surface		121.53		±0.008		121.50
10	Inner diameter sliding portion of bushing (*1)		121.65		+0.013 -0.005		121.73
11	Thickness of sliding portion of bushing (*1)		7		.0.1 -0.1		6.5
12	Thickness of clutch disc		5.4		±0.1		4.8
13	Backlash between input shaft and PTO gear		0.18 - 0.46
14	Clearance between PTO gear and bearing		Standard size	Tolerance			Standart clearance	Clearance limit
				Shaft		Shaft
			65	+0.030 +0.011		. 0.015 -0.015	-0.045 - -0.011	-
15	Clearance between bearing and case		120	.0.015 -0.015		+0.010 -0.025	-0.025 - -0.025

*1 Refer to "Method of measuring dimension of bushing sliding portion"

Method of measuring dimension of bushing sliding portion

Measure inner diameter (A) and thickness (B) of bushing sliding portion with output side bushing (2)
and input side bushing (3) installed to outer race (1).

Power transmitting route

1. When lockup clutch is "disengaged"

Drive case (4) is disconnected from boss (8) and turbine (7) and lockup torque converter works as an ordinary torque converter.

The power from engine > Output shaft > Front drive shaft > Coupling (1) > Input shaft (2), clutch housing (3), drive case (4) and pump (5) rotate together > Oil is used as medium > Turbine (7) and boss (8) > Transmission input shaft (9)

~ The power transmitted to input shaft (2) is also used as power for driving the pump after being transmitted through PTO gear.

2. When lockup clutch is "engaged"

Drive case (4) is connected to boss (8) and turbine(7) and lockup torque converter is locked up.

The power from engine > Output shaft > Front drive shaft > Coupling (1) > Input shaft (2), clutch housing (3), drive case (4) and pump (5) rotate together > Lockup clutch (6) > Boss (8) > Transmission input shaft (9)

~ The power transmitted to input shaft (2) is also used as power for driving the pump after being transmitted through PTO gear.

Oil flow

• The oil flows through the main relief valve and its pressure is reduced to below the set pressure by the torque converter relief valve. It then flows into inlet port (A), goes through the oil passages of stator shaft (1), and flows into pump (2).
• The oil is given a centrifugal force by pump (2), and then it enters turbine (3) to transmit its energy to turbine (3).
• The oil from turbine (3) is sent to stator (4) and flows into pump (2) again. However, part of the oil passes between turbine (3) and stator (4) and is sent from outlet port (B) to the oil cooler to be cooled. It is then used to lubricate the transmission.

Torque Converter Valve

No	Check item	Criteria (Unit: mm)					Remedy
1	Clearance between the torque converter relief valve and valve body	Standart size	Tolerance		Standart clearance	Clearance limit	Replacement
			Shaft	Hole
		32	-0.035 -0.045	+0.016 +0.016	0.035 - 0.061	0.081
2	Clearance between the main relief valve and valve body	32	-0.035 -0.045	+0.016 +0.016	0.035 - 0.061	0.081
3	Clearance between main flow rate selector valve and valve body	25	-0.035 -0.045	+0.013 +0.013	0.035 - 0.058	0.078
4	Clearance between check valve and valve body	25	-0.020 -0.041	+0.052 +0.052	0.020 - 0.093	0.113
5	Main relief valve spring	Standart size			Repair limit
		Free length	Installed length	Installed load	Free length	Installed load
		123	99.5	1213.2 N {123.8 kg}	119.3	1153.8 N {117.6 kg}
6	Torque converter relief valve spring	137	93.5	331.2 N {33.8 kg}	132.9	315.0 N {32.1 kg}
7	Poppet spring (Torque converter relief and main relief)	26	17.0	32.0 N {3.3 kg}	25.2	30.8 N {3.1 kg}
8	Main flow rate selector valve spring	95	55.5	96.7 N {9.87 kg}	92.2	91.9 N (9.38 kg}
9	Check valve spring	45	30	3.97 N {0.41 kg}	43.7	3.82 N {0.39 kg}

10. Solenoid valve for main relief valve
11. Solenoid valve for main flow rate selector valve
12. Oil pressure switch for main relief valve
13. Oil pressure switch for main flow rate selector valve

Main flow rate selector valve

Outline

This valve switches the amount of oil to be fed to the main relief valve.

If one of the 2 charge pumps is enough to secure the main pressure, oil from the remaining pump is flown to the torque converter bypassing the main relief valve. This arrangement reduces the pump load and improves the fuel consumption.

This switching takes place automatically responding to the engine speed being set at each gear speed.

Operating condition

Gear Speed	Engine Speed (RPM)
	From ON to OFF	From OFF to ON
F1, F2, RL, RH	1,000	1,100
N	1,450	1,550

Normal operation takes place at F3 - F7.

Principle of operation
When the solenoid is "de-energized" (When oil from the pump is merged)

When current is not conducted to solenoid (1), oil pressure force does not work on chamber (A). Thus, main flow rate selector valve (2) is pushed to the left by spring (3).

In this case, all of oil delivered from pumps (B) and (C) flows through main relief valve (4) to the torque converter.

When the solenoid is "energized" (When oil from the pump is divided)

Conducting current to solenoid (1) generates oil pressure in chamber (A). Thus, main flow rate selector valve (2) is pushed to the right.

In this case, oil from pump (B) alone flows through main relief valve (4). And oil from pump (C) flows to the torque converter, bypassing main relief valve (4).

Main relief valve

Outline
This valve has the function of switching the main relief pressure. When a high gear speed (F4 - F7) is
selected and, thus, a lower clutch holding pressure is required, function of this valve reduces the main
relief oil pressure, which decreases the pump load and enhances the fuel consumption.

When solenoid is "de-energized" (RL, RH, N, F1, F2 or F3)

• When current is not conducted to solenoid (1), chamber (A) is connected to the drain port and no oil pressure is generated. Thus, oil pressure in chamber (B) is balanced against force of spring (4), starting pressure regulation by main relief valve (3).
• Main relief pressure: 3.53 MPa {36.0 kg/cm2} (At engine speed 1,900 rpm)

When solenoid is "energized" (F4, F5, F6 or F7)

• As current is conducted to solenoid (1), oil pressure is generated in chamber (A). Thus, oil pressure in chamber (A) is balanced against force of spring (4), starting pressure regulation by main relief valve (3). Since diameter of piston (2) at this point is larger than diameter of chamber (B), the oil pressure as current is conducted to solenoid (1) is adjusted to a level lower than that when current is not conducted.
• Main relief pressure: 2.16 MPa {22.0 kg/cm2} (At engine speed 1,900 rpm)