Datsun Differential Troubleshooting Guide

1978 DATSUN DIFFERENTIAL SERVICE GUIDE

DIFFERENTIAL ROAD TEST AND DIAGNOSIS

INTRODUCTION:

BEFORE you remove the differential from a vehicle, perform a complete diagnosis. Road testing a vehicle to detect exact symptoms is essential for proper diagnosis. This will save time, since you may avoid overhauling the differential because of a noisy transmission or wheel bearing. A complete diagnosis will also tell you exactly where to look for defects during disassembly. Be sure to print out the blank road test worksheet for your records.

Read Background Notes about this Datsun Service Guide

CONTENTS:

Road Test Procedure
Interpreting the Road Test
Diagnostics on the Bench Prior to Disassembly
(#3 information not published at this time)
Read important "Caution" statement
ZP printing instructions
Due to many request zpARTS is attempting to produce a CD version of this manual. To be notified when ready please place yourself on the CD Waiting List.

1. ROAD TEST PROCEDURE

A complete road test includes the following steps.
Make a note of any malfunctions or noises.

ROAD TEST STEPS	Noise Factors
ROAD TEST STEPS	Med	Loud	Clunk	OK
1. Steady acceleration, light throttle.
2. Steady acceleration, heavy throttle.
3. Steady deceleration, from high speed.
4. Light deceleration-on and off accelerator pedal.
5. Cruising at low speeds up to 30 - 45 MPH.
6. Cruising at high speeds 45 MPH and over.
7. Cornering, steady speed at part throttle.
8. Cornering, deceleration and acceleration.
9. Harsh shifts, first to second on straight road and around corners.
10. Vehicle stopped, shift between first and reverse, brake applied.
11. Shift between first and reverse, brake released.

2. INTERPRETING THE ROAD TEST

Use the following Diagnostic Chart to isolate the problem.

Customer Comment	Probable Cause of Defect	Diagnostic Step - Road Test	Final Diagnosis - Shop Test CAUTION (click here)
Whines at high speeds.	(A) Transmission speedometer gear. (B) Defective differential front pilot bearing (independent suspension models). (C) Defective wheel bearings.	(A) Drive vehicle at speeds 45 MPH and over. (B) If whine present on de-celleration, this indicates front bearing or pilot bearing.	(A) With vehicle on lift, use hearing device to locate noise at transmission hous- ing and gear cable. (B) Use hearing device to locate bearing noise at front of differential housing and to make sure that the noise is not caused by wheel bearings or transmission problems.
Whines or howls at low speed under a load (heavy throttle or when 2 or more passengers occupy vehicle).	(A) Defective rear pinion bearing. (B) Improper pinion height causing poor tooth contact area.	(A) Drive vehicle at low speeds up a hill if possible, and under a load. If noisy, see (b) shop test. (B) Check noise factor on decelleration If present, see (b) shop test.	(A) Using a hoist or jack and stand, run the vehicle to verify loudest noise using hearing device. Replace rear pinion bearing. (B) If noise is present on both acceleration and deceleration, it is most likely caused by improper pinion height. Be sure to take a pattern reading.
Whines or howls on deceleration only.	(A) Improper backlash. (B) Improper pinion height.	(A) Drive vehicle at all speeds. (B) If noise only present on deceleration, the problem can usually be corrected by adjustment of backlash or pinion height. If backlash is incorrect, you will also feel a slight clunk if you accelerate and decelerate quickly.	(A-B) Testing on a lift will usually not be beneficial as you would not hear the noise factor without de- celeration load. Disassemble and check tooth pattern.
Clunks when shifting or going around corners.	(A) Differential hangers, bushings loose or worn. (B) Improper clearance of side gears. (C) Spider gear shaft worn. (D) Improper backlash.	(A) Drive vehicle and shift under load and no load conditions. If the differ- ential hangers are loose or the mounts are defective, the clunk will be heavy and felt through the entire body. (B-C-D) If more of a knocking sound, drive the vehicle around corners while shifting. This will in- crease the clunk effect.	(A) Check on hoist using pry bar. Replace defective parts. (B) If the vehicle clunks while testing on straight road, this indicates improper backlash. (C) If the vehicle clunks on straight roads when shift- ing and around corners, this indicates side gear clearance. Readjust or replace side gears.
Howls or growls at all speeds	(A) Defective gear set (B) Defective side bearings. (C) Rear wheel bear- ings.	(A-B) Drive vehicle at various speeds to determine if noise changes tone under load or coasting. (C) Drive the vehicle around corners to see if the noise level is high around right or left turns.	(A-B) If the noise level changes very little, the problem is most likely bearings. If the noise level changed excessively, it is most likely the gear set. (C) If the noise level changed around corners, jack up one wheel at a time (use jack stand). Run in gear while one wheel is lock- ed. Observe noise factor change. Use hearing device to isolate the loud- est area (wheel bearing or side bearing).
Leaks	(A) Front case pinion shaft seal. (B) Cover gasket. (C) Loose plug.	(A) Road test to verify that the leak is not accompanied by a noise indicating a defective pilot or front pinion bearing.	(A-B) Place the vehicle on a hoist and inspect for loose pinion shaft seal or defective gasket. (C) Check the drain plug and plug socket (may be cracked around housing).

CAUTION ZP Note: Attempting to perform the shop tests at home on jack stands or other such unstable lifts or supports is extremely dangerous to attempt where the listening device requires a person to get under the vehicle while the drive components and rear wheels are turning. Loose clothing, jewelry and limbs can become easily caught in turning drive shalfs and other components resulting in severe injury or death. The possibility of the car falling off unstable supports and running over the tester is also a very real danger. An idling engine has enough power to make hamburger of a person that becomes entangled in the revolving components.

This last test should only be done by a qualified mechanic using proper lifts, tools and experience. Do not attempt this last test at home.

Notes about this Datsun Differential Service Guide.

The above information, aside from my own ZP Notes, is a very faithful HTML reproduction of the first 3 pages of the "Diagnosis" section of a Datsun Factory training manual produced exclusively for the training of it's own mechanics in the diagnosing, repair and overhauling of the Datsun "H" and "R" differentials used on the majority of their vehicles up to 1978 (and later). This information is from the 2nd edition published in 1978. The first edition was published in 1974.

The HTML pages have been laid out to look very close to the original manual pages. All data has been aligned across the chart in order to make it easy for someone trying to troubleshoot problems to study it online or print it out on a printer. The Road Test Procedure Chart has been setup to allow a person to print it out at home to use as a blank worksheet form to write Dow his test observations on. Late, those notes can be used to analyze his observations using the interpretation chart above.

Printing instructions. From my end, using Netscape Communicator 4.04, the top chart will print out as black type on white and a gray highlight overtones. Unless your browser is set to print out colored backgrounds all yellow and blue chart backgrounds will print out as very light gray, leaving a very useable set of pages for your Tech Library. The colors in the chart were chosen for monitor viewing only. Let me know of you have troubles so I can correct it for all that come later. Top of Page

This service guide was brought to me 2 years ago by a Nissan master mechanic which pointed out the excellent and clear instruction qualities of this guide as well as one that covered the fuel injection systems up through 1978. Although, many Nissan factory manuals have somewhat overlapping information to what is presented here, I have always regarded this factory training diagnosis and overhaul guide superior to others I have seen.

My assessment is that many owners of older Datsuns in the present day are frequently faced with the numerous problems developing in the older Datsun rear ends. It seemed that it might be timely to reproduce such a fine quality trouble shooting guide as this one. There is another 3 pages full of relevant photos and text in the Diagnosis section that I may reproduce a bit later. The entire Differential Service Guide is 172 pages and covers theory of design of both the H type solid axle and R type independent rear ends. If I receive sufficient requests to publish more of the guide I will try to add to what is above. Please let me know what interests you about this kind of information so I can consider what else to work on. Perhaps a CD in Adobe Acrobat format? Please give me some feed back if interested or if this info is helpful to you.

Regards, Eric Neyelin - Z PARTS e-mail: eric@zparts.com Website: http://www.zparts.com

ZP Home Page

Top of Page

ZP Tech Section

Classified Ads

This page last updated November 19,1999

Differential Service Guide produced by the Nissan Motor Corporation 1978

Lay out and page design by Eric Neyerlin.