BW35 Whine

keynsham1

Active Member
#1
My BW35 gearbox whines with a noise like a straight cut gearbox in first. The noise completely disappears in the other gears. The box seems to work perfectly apart from this noise. Any ideas what it could be?
 

harveyp6

Well-Known Member
#2
The normal cause is a blocked filter, but that's going to be noisy in all gears, (including P&N) but often as the speed increases you can't hear it over the normal road noise. If it isn't the filter it could be a problem with the gearset.
 

keynsham1

Active Member
#3
I was wondering if it could be the forward brake band. From reading the Rover manual, it would seem that the forward brake band slips when in first but locks when in second and top. As the noise only occurs in first, it seems to be the only part and action common only to being in first gear. Any worn gears I would assume will make noise all the time as they are always meshing and rotating although possibly not under loads?
 

harveyp6

Well-Known Member
#4
The front band is only applied in SECOND. It's not applied in FIRST or TOP so effectively the drum does slide around inside the band. First gear in "D" is the front clutch and the one way clutch in operation, first gear in "1" is the front clutch and the rear band, so if the noise is there in "D", but not in "1" it could be the one way clutch. I doubt it, but there's an easy way to try to find out if it's a possible. All the gears in the gearset are in mesh all the time, but they're not all under load all the time.
 

keynsham1

Active Member
#6
I will try driving it in "1" and see if the noise is still there. I have never tried the car in "1". Sounds surprising but I only ever drive it in "D", and occasionally "2". It's no sports car and 48 years old so I tend to treat it with care! I will try it in "1" and see what happens!
Ironically the first time it made the noise (noticeably, although I am sure first in "D" was always a little noisy) as far as I can remember was when I overfilled the gearbox. It is a NADA with the filler underneath and it is a complete bugger to fill and top up, especially with the engine running! I drained some fluid out at the time and I would have sworn it was quieter. It is really difficult to remember though. It must be something specific because the noise completely goes once changed into second and top so whatever it is, it is directly related to being in first gear and in "D".
 

keynsham1

Active Member
#7
So eventually I decided it was time to see what was wrong with my gearbox as the noise wasn't getting any better.
First fun was getting it out! Luckily I had also decided to remove large parts of the engine to sort an oil leak from the rear seal of the valley gasket so gearbox and bell housing top attachment bolts could be accessed from the engine bay!

DSCN0173.JPG
DSCN0166.JPG
DSCN0187.JPG
DSCN0162.JPG
Pic 02.jpg

The box has now been disassembled and this is the result:

001.jpg

002.jpg

007.jpg

008.jpg

009.jpg


The summary so far is this:

1) Whining - The reason why you are experiencing excessive noise is because the forward sun gear (which transmits drive in first and second gear) shows evidence of tooth damage. See pictures with white arrows. There is a ‘pitting’ effect on the gears. As a result, the sungear and the gears associated with this part (also known as the planetary gear cluster set) will have to be replaced.

2) Brake bands are worn, one much worse than the other. See picture, these will be replaced with new.

3) Clutch plates again are worn and are near the end of their life. These will be replaced with new, see pictures.

4) Although you wouldn’t have been aware, when I stripped the gearbox down I found two rogue bolts lying in the sump. It appears the gearbox has been overhauled before and these bolts were not tightened and fell out of the valve body. They could have ended up in the gears and this would have caused serious problems!

So it would seem a full overhaul was due!
 

mrtask

Well-Known Member
#8
Ouch!
What is the white cylindrical thing at the back of the drivers side of the gearbox, visible in the fourth and fifth photos?
 

keynsham1

Active Member
#9
Its the refill tube! It's from a USA spec NADA car. They have no filler in the engine bay. Instead, it has a plastic tube with a cap fitted with a bayonet-type lock. Its a real pain and very time consuming to fill. And you have to lie under the car when it is running to check the fluid level!!

0001.jpg 0002.jpg
 

mrtask

Well-Known Member
#11
I imagine topping up the gearbox is entertaining. Presumably this was deemed to be too much fun and the engine bay filler tube was devised to ensure owners didn't get too jolly. I like the fact that the tube and mounting flange are transparent. Is it a combination fill tube and level sight?
 
#12
A lot of NADA's were retrofitted (probably while still while under warranty) with a normal dipstick - mine was... Don't know if it was some kind of official recall or what...??....
 
#13
Way to clean for it to be my thumb Harvey :)
Looking at the face of the sun shaft it is showing signs of wear, looks like the needle bearings are shot too.
Unusual for the front needle to wear badly it's usually the rear one that suffers most.

Be a good time to convert to dipstick and filler and be gone with the sight tube.
 

keynsham1

Active Member
#14
I was just looking through some old posts on this forum and found one that mentioned the BW35 serial numbers and identification plate colours and what they were used on. The plate on my gearbox from my NADA car is this:

BW35 Plate.jpg

The serial number starts 9FU which seems very different from all the others mentioned such as 303, 383, etc. Do these numbers and plate colours have any relevance to the box operation/ratios, etc or are they purely identification plates for different vehicle and engine applications?
 
#15
Plate colours and prefix code ( before serial number ) denote what that particular transmission is allocated too vehicle wise, it also denotes as you have mentioned different engine applications.
Each prefix code is allocated to a certain vehicle manufacturer and each prefix code / plate colour is the production sequence at the Borg Warner factory.
When they were first produced new they were built to a certain specification and upgraded / modified along the production run which impacted the prefix code and plate colour.
Later transmissions had fitted the latest and improved parts that were found to be either lacking in the earlier units, or just cheaper to produce, this also takes into account the car manufacturer demands for better more desirable features in their cars, they also deleted parts from production along the production run
Ratios remained the same throughout, but how they operated changed considerably from the very first ones to the last
 
Last edited:

harveyp6

Well-Known Member
#16
Series number Prefixes with letters and numbers were earlier boxes, all numbers were later. Rover were designated FU. The trouble was that often modifications occurred during the production run without altering the prefix. The 7FU was brought in beacuse it was the first with the PRND21 selector pattern, but during the run it got the self adjusting front servo, and the short kickdown cable, but without changing the 7FU prefix, and P6B boxes were still different to P5B boxes, that didn't rationalise until the 267 Series. Add in the 45+ years since the last boxes were made and fitted, and now any box can contain pretty much anything.
 

clive P62

Active Member
#17
A lot of NADA's were retrofitted (probably while still while under warranty) with a normal dipstick - mine was... Don't know if it was some kind of official recall or what...??....
Many of the sight glasses leaked, my NADA was upgraded to flexible later type tube for that reason, was reported by first owner and fixed under warranty.
 

keynsham1

Active Member
#18
I am getting my BW35 and torque converter back next week after a full rebuild. I know it is an old question but I have been looking at oils and I am aware that the word' Dexron' strikes fear an all BW35 and 65 owners. The oil recommended to me is Comma AQM mineral oil :

Capture.JPG

It says on the label 'Recommended by Comma for certain applications requiring Dexron II and IID. Am I right in thinking that this is an alternative oil that is not Dexron? I assume it has similar properties without the damaging additives of Dexron (Sperm whale oil, Jojoba oil, etc... Google it!!)?

Correct me if I am wrong!!
 
Top