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Discussion Starter #1
hello after tear down of the differential of my GT I need a new ring and pinion, the post on rebuild on here from last week lists splendid with a gear set but cannot find it on their site and he said 850.00 which i am sure are euro. scouring the forum i keep finding the debate of crush sleeve and Isuzu bearings will fit but the Isuzu crush sleeve only works with the Isuzu pinion and talk about a 3mm spacer. Can someone please tell me what Isuzu ring and pinion can replace the original GT and what modifications need to be done? it is a late style axle with no clips and the car was supposedly originally an automatic so not sure of the ratio. quite honestly i was so PO'ed i just kicked it into the shop corner and walked away. I have a 73 in the yard but am trying not to waste the time of swapping them to hear the firetruck behind me with that one also.:no::ugh1:
 

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Opeler
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Can you explain why it is you need to replace the gears?

There are new and used gear sets for sale on German ebay. You probably want to know what ratio you want before you start searching. If you do need another gear set, now is the time to change the ratio. I can't address your Isuzu questions but someone else may be able to tell you where to find crush sleeves for the Opel.
 

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Discussion Starter #3
Can you explain why it is you need to replace the gears?

There are new and used gear sets for sale on German ebay. You probably want to know what ratio you want before you start searching. If you do need another gear set, now is the time to change the ratio. I can't address your Isuzu questions but someone else may be able to tell you where to find crush sleeves for the Opel.
the ring gear is pitted and the wear pattern is way to low on the heel, it whines horribly when in 4th gear with no load just at highway speed so it is definitely gear wear. I got a GT crush sleeve from OGTS i just know if i put it back together the ring gear will flake and burn up 500.00 worth of new bearings.
 

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Can you explain why it is you need to replace the gears?

There are new and used gear sets for sale on German ebay. You probably want to know what ratio you want before you start searching. If you do need another gear set, now is the time to change the ratio. I can't address your Isuzu questions but someone else may be able to tell you where to find crush sleeves for the Opel.
One has to remember that the original diff carrier only can take 3,44:1 or 3,18:1 gears without a 3mm ring gear spacer. Gears from 3,67:1 and numerically higher have a different carrier.
 

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Just Some Dude in Jersey
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PJRomano is the only Opeler I can recall who has rebuilt his rear axle. It's not a job for the squeamish. You more or less have to guess what thickness shims you need, laboriously disassemble and put it all back together, and HOPE it works. If you were incorrect with your guess you have to take it all apart again, throw away the crush sleeves and start over with your next best guess.

Personally, I wouldn't spend one second rebuilding one. Ones from cars with automatics are usually in great shape, manual trannies wear out the entire drive train because everything is locked together with no slippage, so every bump in the road goes straight to your piston rings and every other part. Every time you ease off on the gas pedal every part of the drive train now gets reverse wear at all the contact surfaces. This effect is greatly lessened with an automatic and it's torque converter. Guys with stick shifts tend to drive like Mario Andretti, guys with autos tend to drive a bit tamer.

So I would suggest trying to find a rear axle from an auto tranny car. Even if you have to buy it from California and have it shipped, I feel that the cost of shipping is well worth the price to avoid the chore of rebuilding one.

OGTS has the shims and crush sleeves if you want to go ahead and rebuild the one you have.

:veryhappy
 

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Spaceman
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329 Posts
@mgwinner,

Splendid Parts do not have a ring & pinion set, they do however have a complete rear axle bearing set, should you come in need of that.

As @Commodåren states 3.18 & 3.44 carrier / housing is the same, but if you want to go 3.67 or 3.89 you have to purchase a new carrier / housing.

ATZ teile, https://atz-online.com/ have all of the above, but they are eye-watering expensive, around 1100$ for a ring & pinion set, a new carrier 392$, and if you need new spider gear, you have to dig deep into your pockets, as a set is around 522$...- plus shipping.

You might be able to source used parts on ebay.de. Trouble is that they could be worn as well. I have also searched and heard about the Isuzu solution, but I'm unfortunately not in a position to advice. I'm handing over my diff, well actually the hole rear axle to a professional to do the rebuild.

Cheers.
 

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Discussion Starter #7
well Scifi Guy just explained the beauty of a 9 inch ford diff. This was an automatic car originally and the guy swapped it when the tranny started to slip badly. I was an auto mechanic for 30 some years and worked nights in a 4wd shop so I have rebuilt more differentials than i care to remember, for those who come across this post in the future some helpful advice, The crush sleeve is NOT needed to set pinion depth only for final assembly and bearing pre-load, leave it out until all is correctly set. if you are replacing your old bearings hone the center hole of the old ones with a cylinder hone to reduce the press fit from .002 to .0005 a nice snug press fit and when you want to re-shim things the bearings press right on and off with ease. dykum dye will give you a wear pattern and you want horizontally centered on the ring gear teeth and NO contact on the vertical top edges of the teeth.
 

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Discussion Starter #8
@mgwinner,

Splendid Parts do not have a ring & pinion set, they do however have a complete rear axle bearing set, should you come in need of that.

As @Commodåren states 3.18 & 3.44 carrier / housing is the same, but if you want to go 3.67 or 3.89 you have to purchase a new carrier / housing.

ATZ teile, https://atz-online.com/ have all of the above, but they are eye-watering expensive, around 1100$ for a ring & pinion set, a new carrier 392$, and if you need new spider gear, you have to dig deep into your pockets, as a set is around 522$...- plus shipping.

You might be able to source used parts on ebay.de. Trouble is that they could be worn as well. I have also searched and heard about the Isuzu solution, but I'm unfortunately not in a position to advice. I'm handing over my diff, well actually the hole rear axle to a professional to do the rebuild.

Cheers.
thanks for the info i kinda thought it was going to go that way......for 2500.00 ill cut down a F9 and be done with it. I also laughed and loved how a 1 inch axle has 1/2 inch splines for the spider gears, gotta love the Germans.
 

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Opel Key Master
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Talked with you on the phone today, and no, don't mess with any Isuzu parts, the rear differential parts are available.

Gordo, they do make measuring tools that will tell you how much shimming the pinion will need, and shown in the factory service manual.


If I were you, since you have been into differentials before, get a good used one, pull out the chunk with the ring and pull the pinion and the inner bearing race to get the shims for that gear set...then you do not need to do any measuring, simply add the shims back, or replace with the same thickness, and then set your pre-load. I have posted 3 videos of setting the pre-load on YouTube, if it helps. New bearings are different from used bearings as far as pre-load. You can buy all the bearings, although they are expensive
 

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Spaceman
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329 Posts
I'm so looking forward to get rid of the whining. I'm also quite curious to find out if I have a 3.67 instead of the standard 3.44.

At 100 km/h (GPS reading), in 5'th gear (Getrag 240, ratio 0.81), I read 2650 - 2700 rpm., and I'm running on 185/70/r13 wheels. So when I do the math I get a 3.67 axle ratio (final), but I can't believe that previous owner should have changed the standard 3.44. If I really do have a 3.67 I could be very tempted to go 3.89.

@opelspyder, could you by any chance link to the 3 videos you have posted on you-tube setting pre-load, can't find them.

Cheers
 

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Opeler
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I'm so looking forward to get rid of the whining. I'm also quite curious to find out if I have a 3.67 instead of the standard 3.44.

At 100 km/h (GPS reading), in 5'th gear (Getrag 240, ratio 0.81), I read 2650 - 2700 rpm., and I'm running on 185/70/r13 wheels. So when I do the math I get a 3.67 axle ratio (final), but I can't believe that previous owner should have changed the standard 3.44. If I really do have a 3.67 I could be very tempted to go 3.89.
Yes, you have 3.67 differential. The picture shows rpm vs. speed with 3.44 differential in 5th gear.
I would not recommend 3.89 in the GT for the street and road. First gear is already ridiculously short which makes it almost unusable with 3.89 differential, not to mention increased noise and fuel consumption at highway speed.
 

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I'm so looking forward to get rid of the whining. I'm also quite curious to find out if I have a 3.67 instead of the standard 3.44.

At 100 km/h (GPS reading), in 5'th gear (Getrag 240, ratio 0.81), I read 2650 - 2700 rpm., and I'm running on 185/70/r13 wheels. So when I do the math I get a 3.67 axle ratio (final), but I can't believe that previous owner should have changed the standard 3.44. If I really do have a 3.67 I could be very tempted to go 3.89.

@opelspyder, could you by any chance link to the 3 videos you have posted on you-tube setting pre-load, can't find them.

Cheers
The fifth gear ratio is 0.804. Are you sure that the factory tach shows the true RPM ? Perhaps you should take a look under the cover to see what the ratio is, either by dividing the ring gear teeth with the pinion gear teeth or, if possible, see what ratio is engraved on the ring gear.:)
 

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Yes, you have 3.67 differential. The picture shows rpm vs. speed with 3.44 differential in 5th gear.
I would not recommend 3.89 in the GT for the street and road. First gear is already ridiculously short which makes it almost unusable with 3.89 differential, not to mention increased noise and fuel consumption at highway speed.
Denmark is a relatively small dense populated country and half of it consists of islands so a 3.89:1 wouldn't be so bad on the local roads if you ask me, but that is of course just my personal opinion. Besides, I understood that he got the bug for track days after driving at the Sturup track in Sweden.
 

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Spaceman
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@Commodåren,

No, the factory tach might not show the actual rpm. precise enough, but I'm not going to remove the cover as I'm only a 1½ week away from handing over the "problem" to the work shop. I'll be pleasantly surprised if reality shows a 3.67.

Yes I got the bug for more track days after my visit at Sturup in Sweden :yup:

My friend Asger want us to go on ring Knutstorp next spring, probably because the track layout suits his JAG E-type and his 240hp, much better. He wasn't thrilled that I could keep up with him at Sturup. Truth is that he is riding on original springs and dampers, where mine are relativ new koni's, lowering springs, etc., so in the corners he didn't stand a chance.

Cheers
 

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3.89 axle ratio and Getrag 240 is a nice combination. You end up with 3.13 final drive ratio which still allows for high speed driving but greatly improves low speed acceleration.

I had this in one of my cars with a 97 hp 1.9 liter engine and it was very fun to drive.
 

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The fifth gear ratio is 0.804. Are you sure that the factory tach shows the true RPM ? Perhaps you should take a look under the cover to see what the ratio is, either by dividing the ring gear teeth with the pinion gear teeth or, if possible, see what ratio is engraved on the ring gear.:)
I thought if you jacked up 1 rear wheel and turned it 1 revolution the driveshsft would turn 3.67 times (making it easier to compare, 6 revolutions of the tire would be 22 at the drive shaft. The 3.44 rear would make slightly less than 21 turns so it should be easy to determine. Of course, if you have a limited slip differential (or locked!), it won't work IIRC.

The difference between .81 and .804 in 5th would be about .04 at the rear axle so, not a 3.44.

Doug
 

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3.89 axle ratio and Getrag 240 is a nice combination. You end up with 3.13 final drive ratio which still allows for high speed driving but greatly improves low speed acceleration.
This is what I have in my GT but I also have 1986 Isuzu Impulse gears installed into a Buick Opel rear. I do not have the stock carrier since I have a Gripper LSD in my car. I did the work on my rear axle and it was not easy, but I have no whine at all.
 

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Opeler
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I guess, choice of differential ratio is personal preference and how you use your car. Also, larger displacement engine (I run 2.5) provides plenty of power and torque for brisk acceleration even with standard differential. I mostly drive long road trips, so when I added Quaife LSD, I made special effort to keep standard 3.44 diff ratio. Two days ago I drove my GT eleven hours from Pennsylvania. I certainly enjoyed keeping 75 mph at some 2600 rpm. But for smaller engine short ratio could certainly be fun when jumping from traffic light to traffic light or for the track event.
 

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Spaceman
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Gentlemen, thank you all for your contribution, whether I should go 3.89 or not

@mgwinner, sorry to have "hacked" your post, and I excuse for the slight detour it have taken from you original question. Don't mean any harm.

Cheers
 
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