Rear end Noise

[jeffw]

Got to like the title
Finnally got the car on the road
must say its been a blast, keith the tips on the "no start seeems to be working !
I cleaned te ground strap from the motor to the chasis but it was not until I cleaned the battery to chasis did it get get resolved.
As for the the OPG turns out that it was justa wire off
Thanks Baz the problems was as stupid as it sounds was finding it sensor
it was located directly behind the exhaust
luckly I was doubled jointed.
Now for my next question
Sounds like the rear Diff is making a humming sound especially in 4th gear
over 60 MPH it gets really loud
I was going to change the Diff oil and wanted to confirm how
there is one allan key plug
if I loosen the bottom bolt to allow the oil to drain then fill to the allen key plug is this the correct method?

any suggestions to what else may be causing the noise?

regards
Jeff

[jeff denton]

Take out the bottom bolt, take out the allen plug on the cover, catch the oil in a clean shallow pan. Look at the oil, is it silvery? That is metal particles from parts wearing out against each other. Does the oil smell really gross? Then it's been in there way too long. Is the oil kind of milky looking? Then it has water in it.
Anyway, then put the bottom bolt back in and fill through the plug hole till no more goes in. Put some miles on the car and change the oil again. Keep looking for silvery particles, keep changing the oil till you don't see them.

[jeffw]

jeff I removed the plug and even with the car jacked up on tha right side oil came out
it was a golden color
not sure of what I was doing I put the plug back in
the oil did feel gritty
do you think that repalcing the oil will resolve the problem or am I soon in the market for a new Diff?
jeff

[opelgt73]

I would say junk it and find another one. No amount of chaning the oil is going to get rid of the problem.

On one of my GT's there was a howl whenever you let off the gas over say 50mph, I drained the diff and took a look inside. The gears were toast, I can't believe it ran as long as it did. So I swaped it out for another one.

[jeffw]

Did you rebuild or swap it for another
Jeff

[opelgt73]

Originally Posted by jeffw Did you rebuild or swap it for another Jeff

Swaped it. Removed the "new" rear end from a parts GT. Removed all the brake components from the old one and installed them on the new one. Actually did the entire swap start to finish in about 2 hours. In the driveway of a fellow opeler!!!

[GTJIM]

The parts and bearings to rebuild an Opel diff either cost an arm and a leg - or cannot be found!
Just one point - get a later model GT diff from 1972 or 73 as they have the later style of conventional wheel bearings - the earlier ones have roller bearings which run directy on the axle shaft - and are very hard to find.
Thelater diff has a plastic breather on one axle tube - the early one a metal breather (Tiny pressed sheet metal thing in the top of the tube - with a wee "hat" on it!).

[jeff denton]

Both diffs I worked on had the front pinion bearing ate up. Others were fine.
If you swap rear ends be sure to use the later style! Be forewarned that the brake backing plates don't quite interchange from early to late, though. Get the entire unit complete with brakes.
Jim is right on about the bearings. No problem to find, but expensive!!!
Look at all the threads about swapping in an alternative rear end. That would be my preference unless I had to keep it stock for some reason...

[Turbo X]

JEFFW,, I think ebay has a rear end for an opel gt that was rebuilt with shocks, check it out... also when you drain the oil , take the cover off and wash it out with solvent, and check for wear. put the cover back on using gasket sealer, add 90wt oil to 115wt , make sure to check your universal joint, they will make same sound when worn.. and its not hard to change the gearing in the rear end with another set..turbox

[Turbo X]

here some more info for you.
Reply to Letter about Rear Axle Noise Diagnosis, 1 page
Describes conditions possible to diagnose rear axle noise; Noises only on turns indicates worn axle or carrier bearings, high pitched whine starting at very low speeds indicates worn pinion bearings, and a noise when coasting 40-50mph (in neutral, with no acceleration) indicates worn ring and pinion gears.

Gear Oil Change, Transmission & Rear Axle; 1 page
Roger L. suggests Kendall 80-85-140W "three star"gear oil, and states that removing the lower center bolt is the best method of draining the rear axle, while removing the oil pan is the best method of draining oil from the 1968-1970 "early style" Opel manual transmission. (The later 1971-1975 Opel manual transmissions can be more easily drained by unscrewing and removing the cylindrical rear-mounted reverse switch. Oil refill capacity for the rear axle is 2 1/4 pints, and another 2 1/4 pints will refill the manual transmission.

[jeffw]

I have drained the diff replaced the oil ran it for a while and last night drained and removed the cover. no sigh of any metal or ware that my untrained eye could detect.
there did seem to be some backlash when I rotated the wheels. would these pictures help? I refilled the diff, and ran it while on the stands.
there seems to be some noise from the u-joint area. could this be whats causing the noise?

[baronbors]

Originally Posted by jeffw there seems to be some noise from the u-joint area. could this be whats causing the noise?

How are your center supports and donut?

[jeffw]

Originally Posted by jeffw I have drained the diff replaced the oil ran it for a while and last night drained and removed the cover. no sigh of any metal or ware that my untrained eye could detect. there did seem to be some backlash when I rotated the wheels. would these pictures help? I refilled the diff, and ran it while on the stands. there seems to be some noise from the u-joint area. could this be whats causing the noise?

I ran the car while on stands, there was noise coming from the propeller shaft centre support area
Any known problems

[kwilford]

Originally Posted by jeffw I ran the car while on stands, there was noise coming from the propeller shaft centre support area Any known problems

There is a bearing in the central joint on the rear drives shaft, hidden inside the rubber "Donut". It can happen that as the donut deteriorates, it allows dirt to get up inside and the bearing gets "crunchy" (new technical term!). On mine, I took it apart to beef up the donut (there are a couple of thread in the early days of the "Central Joint" Forum about "How to Stiffen the Central Joint"; I think it beats your "Rear End Noise"!).

The bearing has a pair of steel covers that "almost" seal it from the elements, but mine had gotten dirt and such inside. I had to pull the entire torque tube assembly off the car, then I removed the rear drive shaft out of the torque tube, and pulled the yoke off (that attaches to the front driveshaft U-Joint). Then the one bearing cover was pulled off (the other is welded to the shaft), cleaned out the bearing, and no more noise. I was worried about the bearing, but it seems fine.

HTH

[jeffw]

Originally Posted by kwilford There is a bearing in the central joint on the rear drives shaft, hidden inside the rubber "Donut". It can happen that as the donut deteriorates, it allows dirt to get up inside and the bearing gets "crunchy" (new technical term!). On mine, I took it apart to beef up the donut (there are a couple of thread in the early days of the "Central Joint" Forum about "How to Stiffen the Central Joint"; I think it beats your "Rear End Noise"!). The bearing has a pair of steel covers that "almost" seal it from the elements, but mine had gotten dirt and such inside. I had to pull the entire torque tube assembly off the car, then I removed the rear drive shaft out of the torque tube, and pulled the yoke off (that attaches to the front driveshaft U-Joint). Then the one bearing cover was pulled off (the other is welded to the shaft), cleaned out the bearing, and no more noise. I was worried about the bearing, but it seems fine. HTH

Last Night while I had the car on stands, I did a little pokeing around the Donut looks worn (go figure after 33 years) I sprayed a little Rust check arround to see if that would make a difference,
I still am little afraid to start taking things apart cause I'm not sure what parts are avaiable and what's not! the last thing I want to do is to have the car laid up because parts are not avaiable, Around here people can't even spell opal
I will poke a little futher tonight see if I can see any dirt around the donut
Did you have to remove the shaft afterall?

There are a couple of leaks that I want to investigate as well
a few theads suggest looking at the speedometer cable area

I was going to fush the Transmission as well
do you know if you remove the transmission cover plate if you will require a gasket or can you use silcone

Jeff

[jordan]

All of the bushings and the torque tube donut are available. I just did mine and I am still surprised every time I upshift and I dont hear a clunk. I believe if you remove the panhard bar and the center support along with the U bolts it will allow you to drop the torque tube down so you can then remove the center support.

[matl59]

I have a howl coming from my rear end when at speed and let off the gas. Started wednesday, I knew there was a reason I should have tools at my apartment This morning I could hear it slightly even when on the gas. Still have to drive it about 60 more miles before I can check it out later today Hope I find some oil in there when I get back to my parents house. Early rear end too, hope it holds together! Oh well this will motivate me to swap it for one of the ones I have with factory sway bar mounts.

[opelgt73]

Originally Posted by matl59 I have a howl coming from my rear end when at speed and let off the gas. Started wednesday, I knew there was a reason I should have tools at my apartment This morning I could hear it slightly even when on the gas. Still have to drive it about 60 more miles before I can check it out later today Hope I find some oil in there when I get back to my parents house. Early rear end too, hope it holds together! Oh well this will motivate me to swap it for one of the ones I have with factory sway bar mounts.

I had that happen to my Yellow GT. I think it was the drive shaft bearing thats on the pumpkin that gave out. Once it is bad you might as well toss the diff gears as they start to get shredded. Just swap it out with a good rear end, it only takes about three hours to swap one out.

[RallyBob]

If the gear oil level gets low the front pinion bearing often gets wiped out. With the early style rear axles, low oil level can also be terminal for the outer axle bearings.

Bob

[matl59]

Yeah, I'm kind of figuring its going to be toast, as long as it gets me home, it owes me nothing. It was pretty well worn when I got the car. If I remember correctly the axle seamed to have about 5 degrees free play back and forth when I rotated it 3 years ago when I first bought it. The axle probably has about 200,000 miles on it with little to no maintenance over the years. I've changed the oil and put about 10,000 miles on it since I first registered it in March of 2005. Really should have checked the oil level about 5,000 miles ago, live and learn i guess

[matl59]

Well, it got me home. Doesn't seam to be due to lack of oil. I'll pull the cover off the back of it in the morning and have a closer look.

[matl59]

Took a closer look at things yesterday. I removed the rear cover and inspected the gears, everything actually looked pretty nice. The pinion gears to the pinion shaft seam to have a bit of play but didn't seam to be chewing its self to bits. I really found nothing alarming so I reinstalled the cover and put some fresh oil in it.

While I was under there I noticed one of my exhaust hangers was missing. Relaced that as well.

Took in for a short spin and no noise. Could have possibly just been the exhaust system vibrating but seams strange that it only did it when I was decelerating or coasting.

[opelgt73]

if there is any play at all in the pinion gear bearing, it needs to be replaced. I'm guessing that the new oil has made the noise quiet for now. I don't remember how long I drove mine with the howling noise, but I think it was after 2 or 3 weeks of daily driving. By then there were tons of little pieces of metal in there.

[matl59]

The play has been there since I bought the car and the noise only just started this week after over 10,000 miles of driving. I'll keep an eye on it for now. I plan on swapping it out for another one in the near future anyway. Just don't really have the time to do it now if I don't have to do it.