Rear Differential Growl?

[Frank Thomas]

I am currently working on a TR7 Spider that has begun to make some strange sounds from the rear differential (I think). The car runs great, and shifts well - but get the car to 45/55 MPH and let off the gas, it makes a very loud growling (lack of a better term)/ vibration and whine from the rear end.

The noise is more pronounced and louder when you are downshifting to slow down.

With the 5 speed transmission, does the propshaft have a cv joint that could be going bad? Or could it be a pinion bearing in the differential that is going bad?

Any ideas or suggestions would be helpful - many thanks!


1980 TR7 Spider

[Underdog]

I would bet on the pinion brgs. Any idea of the mileage?

72 MGB BRG
80 TR8 Persian Aqua
If women don't find you handsome, they should at least find you handy.

[Frank Thomas]

According to the odometer, it has right at 22k miles. It has the original top, and, until recently, the original drive belts from BL on the car; so I think it is pretty closs to accurate. However, one can't be sure....

The wildcard IMO is how the PO drove it - if he was rough (4th gear synchro is a little weak) and he may have done some damage. I did change the fluid in the rear diff a month ago and it was nasty. This has been there since I got the car in early March and I am just getting to the point of wanting to sort it out. I was told it might be the CV joint, but for the life of me, I dont see a joint at the end of the prop shaft, unless it is inside it.

By the way, the diff is fairly quiet (makes some whine) when you have your foot in/or on the accelerator. Its only when you let off that you get the noise from the diff.

Thanks again!










1980 TR7 Spider

[busheytrader]

I just replaced my propshaft which was vibrating and groaning about 10mph further up the scale than yours. The old one had to be replaced as it had worn CV joints at both ends.

I thought it was the rear axle until I dropped the shaft and had it inspected. The splines were worn at both ends and made most noise when lifting off the gas pedal.

It's easy to remove from the car so it might be worth looking at it before you strip down the rear axle.

Adam



TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes, Anti- Dive, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 5 Spokes and Cruise Lights. No Door Stickers. Mine since July 1986, V8 from 1991

[Frank Thomas]

Adam,

I will definately check it out. I guess there are joints inside the propshaft that can't be seen, other than the splines that stick out from either end of the prop shaft? It almost looked like a sealed unit...but nonetheless, I haven't disconnected from the transmission and the rear diff, yet...

Frank



1980 TR7 Spider

[Beans]

Indeed first check the CV joints, they are the weakest (transmission) link.
5 Speed axles are fairly solid.

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[jclay (RIP 2018)]

OK, real cheap check! Lift the gear shift knob straight up. If it goes up a 1/2" or more, then I would say that the shifter housing bushings have perished and the housing is rubbing on the drive shaft when you let off the gas. Also check the rear motor mount (transmission mount) because when they get old and soft, they will let the back of the trans drop down.

jclay

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[Frank Thomas]

Already got put in new shifter bushings on it - that was the first thing I did when I bought the car (thanks to the forum!)

This is strictly a mechanical sound that is really really noisy on the downshift. It could be that mount, as it is somewhat nasty, but I wanted a "second" opinion before tearing into it.

Is there any failsafe way to tell if it is the CV joints in the shaft, and to replace them if that is the problem?

Many thanks!



1980 TR7 Spider

[saabfast]

The propshaft CV joints are effectively the same as the ones on the inner end of Mini driveshafts. The only way I know to check them is to get under and check for obvious play. They are not 'serviceable' as far as know (no kit like with the Hardy Spicer UJ on the 4 speed shaft) but they can be stripped down and repacked with grease and rubber boot, which is often split, replaced with the Mini driveshaft inner one. These are available for a few pounds at shows or from mini specialists. The alternative is to replace the propshaft with one with UJ's from he usual suspects like S&S.

Alan
Saab 9000 Stg 1
Saab 9000 2.3 FPT Auto
'81 TR7 DHC

[Rblackadar]

Ted at TSI I think has the 4 speed prop shaft modified for the cv joint issue. I believe they both have the u-joints on the ends so they are totally serviceable.

[Frank Thomas]

Latest update - I talked to Ted at TSI this morning. He gave me some pointers on how to isolate the issue. Hopefully, over the weekend, I will have a chance to do some testing and checks back there.

Consensus from other people I have talked with tend to think it could be a propshaft cv joint issue. The good news is that if it is the propshaft, Ted does sell a shaft modified with fully serviceable u-joints on the ends, which eliminates the cv joint issue completely.



<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Rblackadar</i>

Ted at TSI I think has the 4 speed prop shaft modified for the cv joint issue. I believe they both have the u-joints on the ends so they are totally serviceable.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

1980 TR7 Spider

[Rblackadar]

Keep us posted....I'm curious

[busheytrader]

The propshaft specialist advised like the others here, that CV joints are unserviceable. The wear wasn't immediately apparent but there were tight spots at various extensions of the splines.

I had a new bespoke item made up which was effectively a shortened SD1 propshaft with 2 x CV joints. It was half the price of one with 2 x U/J's, hence the attraction.

Adam

[Frank Thomas]

Just a quick update on this issue - as the issue is finally resolved.

VB here in the States sells an OEM style driveshaft with CV joints. Since it would be cheaper (and overall better to my sanity) than having to take apart the rear axle, I went ahead on a whim and ordered one and finally got it installed late last week.

And, since replacing it, all of the noise coming from the car is gone. Upon inspection of the old driveshaft, the boots were not torn. However, the joints are very "loose" compared to the new one. Unfortunately, I am not an expert at CV joints, but just from looking the two shafts side by side, there certainly is something wrong with the old shaft.

Many thanks to all!!! Now, I need to replace the rear motor (transmission) mount...

Frank




1980 TR7 Spider

[bmcecosse]

Good to hear that sorted the problem - I have been wondering baout the CV joints for a while. The inner 'Mini' ones seem to go on for ever, on a Mini - they don't get much articulation.