How much is the rear end good for & why?

[CoriolisSTORM]

Alright gents, I'm going to search after this, but anyway, how much HP and torque is the rear end on an Opel good for? What is the weak link in the rear end? I've seen 100 HP or so thrown around, is this a decent safe number? What about torque wise? I'd think some stronger shafts and slightly less heat treated gears would be good for it from what I've read.

[Paul]

It sounds like shock loading of the components is the biggest factor in spread of the number range you will be receiving from different folks. For instance, if the differential is open and the tires are of the street variety, the power levels will be much higher than if sticky "R" compounded tires and a limited diff is used. Also, I remember reading, as one level of weakness of solved then another appears.

So, IIRC, the spider gears are the first weak point followed by the shaft inside the torque tube. What the absolute capacity levels are, IDK, but will be watching to see what shakes out......

[CoriolisSTORM]

haha, I'd like to avoid shaking stuff out. This thing reminds me of a Jeep Dana 35 rear axle, there's a saying about kicking the rear tire and if it falls off, its a Dana 35 rear end. Broken differential parts (specially when you cant convert it to FWD like you can a jeep, at least temporarily) will ruin your day rather quickly. So putting in a limited slip would be helpful? What do you mean by the shaft inside the torque tube? This discussion is going to influence my engine selection.
edit: Can it withstand a VW TD?

[namba209]

I would guess it depends on what you're going for. I've got 160 advertised HP in Willit? with about 200 ft. lbs. of torque. A drag racer it will NOT be. RallyBob has stated here on the site he's destroyed numerous rear-ends wih stock HP. The weak link according to Bob is the splined shaft inside the torque tube that engages the gear. He also said that with my ZF posi, I should be good to about 250 HP. But I'll let others, more knowledgeable, advise you.

[opelnut10]

Originally Posted by namba209 I would guess it depends on what you're going for. I've got 160 advertised HP in Willit? with about 200 ft. lbs. of torque. A drag racer it will NOT be. RallyBob has stated here on the site he's destroyed numerous rear-ends wih stock HP. The weak link according to Bob is the splined shaft inside the torque tube that engages the gear. He also said that with my ZF posi, I should be good to about 250 HP. But I'll let others, more knowledgeable, advise you.

The weakest link I found to be the spider gears, and i can assure you I tested every part of the Opel driveline. The spline inside the torque tube propeller shaft will stay togather pretty good as long as the bolts that hold the torque tube to the differental are pulled up tight, and the axles are most likely the strongest parts in the assembly. I would estimate that on a street driven car with street tires in would safely handle 130-135HP unless you really try to break it. The hardest punishment you can give it is from a dead stop with a lot of rev's or cornering with hard acceleration in the corner. Of course there are some people that can tear up a cast iron outhouse with rubber hammerand those folks need something a little more heavy duty. The last drag car I ran had a 8 3/4 MOPAR narrowed up with Summer"s Brothers Full Spool and Axles and a Doug Nash Super T-10 Transmission (pro Shifted with shifting dogs and 9310 nickle gears) that will stay with you with 10 inch drag slicks and 210 HP at 7500 RPM if you are inclined to have a need for it but with a 5:57 gear it is made for short trips only (1/4 mile)

[nobody]

With another gear set (not Opel ) you can push it to over 200 horse and 13 second quartermile runs. I've lunched several 4 speeds and one split the case but never had a diff fail if it was properly maintained.

Try some math. The number who have actually broken a rear end divided by the number of pictures of one destroyed divided by the member list here to give you a true probability of failure. 1 divided by 0 divided by some 5000 is a pretty small number. Prove me wrong. i'd like to know

[CoriolisSTORM]

I'd like to get it the equivalent of a modern TDI eventually. 90 or 100 HP (bigger's better!) and about 150 or 177 or so on torque (different generations ya know) is what the TDI is rated at, keep in mind I'm looking at a TD which is rated significantly lower in HP and torque. I might go a little higher than that but nothing absolutely exciting out of it of course. It would be just a commuter car and such, able to handle it if I really stomp on it, but not a drag racer mind you. So, is it possible to anneal the spider gears so that they aren't as hard and prone to shattering? I read on another thread that they were hardened almost excessively. Thoughts?

[GTJIM]

It is possible to increase the strength and decrease the brittleness of the spider gears by re-heat treating them - the problem is guessing what type of steel Opel used to make them from. Different steels require different temperatures for hardening and annealing. Perhaps heating to around 250/300 degrees Centigrade and letting them cool slowly buried in sand might do the job of drawing down the hardness a bit.

Another avenue worth considering is Cryogenic treatment - the gears are 'frozen' in liquid nitrogen and when returned to normal temperatures are both tougher and more wear-resistant. Worth a look!

!Cryogenic Metals Treatment

[Paul]

Originally Posted by CoriolisSTORM I'd like to get it the equivalent of a modern TDI eventually. 90 or 100 HP (bigger's better!) and about 150 or 177 or so on torque (different generations ya know) is what the TDI is rated at, keep in mind I'm looking at a TD which is rated significantly lower in HP and torque. I might go a little higher than that but nothing absolutely exciting out of it of course. It would be just a commuter car and such, able to handle it if I really stomp on it, but not a drag racer mind you. Thoughts?

Actually, the stock rear end might just handle the output of a TD. Just stay away from drag starts and hard shifts and you might just get away with it... Sounds like it would be worth a try anyway....

[yellaopelgt]

In a everyday driver type car even with a "hot" motor of lets say 150 hp or so, how many people here have actually destroyed a rear end??? I am curious to the actual number. I can see it happening IF the driver was intent on doing this by dumping the clutch at every stop light or getting on it around corners but just normal or a little "spirited driving"?? I've never met anyone that has wrecked one. I actually heard stories of people doing some very hard driving and the rear end has held up for long periods of time, longer than other driveline parts as a matter of fact. Can we get a show of hands?????
Joe

[briarrose]

We haven't seen one fail yet. We went through a period where 4 speed transmissions were like candy but never had a rear end fail.

[blancojp]

Early rear ends do not last however the '72 and '73 rears are very good.
I have been running my V-6 with a TH350 since 1995 with the stock rear end, not see a failure yet.

[opelwasp]

Originally Posted by yellaopelgt In a everyday driver type car even with a "hot" motor of lets say 150 hp or so, how many people here have actually destroyed a rear end??? I am curious to the actual number. I can see it happening IF the driver was intent on doing this by dumping the clutch at every stop light or getting on it around corners but just normal or a little "spirited driving"?? I've never met anyone that has wrecked one. I actually heard stories of people doing some very hard driving and the rear end has held up for long periods of time, longer than other driveline parts as a matter of fact. Can we get a show of hands????? Joe

I can just see it now...
Bob Legere with both hands and feet sticking up in the air.

[briarrose]

It's a valid question Chris, have you or your dad had one let go?

[CoriolisSTORM]

Originally Posted by GTJIM It is possible to increase the strength and decrease the brittleness of the spider gears by re-heat treating them - the problem is guessing what type of steel Opel used to make them from. Different steels require different temperatures for hardening and annealing. Perhaps heating to around 250/300 degrees Centigrade and letting them cool slowly buried in sand might do the job of drawing down the hardness a bit. Another avenue worth considering is Cryogenic treatment - the gears are 'frozen' in liquid nitrogen and when returned to normal temperatures are both tougher and more wear-resistant. Worth a look! !Cryogenic Metals Treatment

Cryogenics is a good idea, its one I had forgotten about, as we did not discuss it much in class. Knowing the exact alloy and such is a problem with these like you said. Its a 1975 rear end, so it should be a little better than the earlier ones right? A TD's power output at stock is, well for the 1.6L anyway, is slightly lower than the standard 1.9L's output. The 1.9L TD is almost the same.