Dealership pre-approved me for a car loan over the phone but wont tell me how much I was approved for. Is that normal they want me to go in?

No, there is nothing normal about this.  EDUCATED buyers find their own loan and then decide what they can afford.

Nope--it's NOT normal. Usually you get approved for a car loan for a PARTICULAR car. Not "in general". If you pick out a car, THEN then do the loan application. They just want you to come into the dealership so they can up-sell you or sell you something they can't otherwise get rid of. 

What they mean by "approval" is that your credit score and your down payment amount will PROBABLY result in a buy. 

The dealer is pulling your leg. You are NOT approved for anything. It's his way of reeling you into his office where he has full control of you. Once you select a car and agree to buy with financing, it is only then that your credit and finances are checked and you are approved -- or not. 

If you want a real pre-approval, go to your local banks and credit unions and apply. Then you'll know whether you are approved and for how much.

You are not approved for a certain amount only any car you want 

Pre-approved just means you are breathing--it is NOT "approved"  That is totally different.

They are salesmen after all and they can't get money on the phone.  When you are there, they can sell you  a car IF you can SHOW THEM THE MONEY.   Then and only then, will they "waste time" talking to you otherwise, watch their commercials on TV.  Every person is different because every income situation is different.

. That is the way it goes.

It should be expected.

. I would NEVER get a car loan from a dealership because their interest is higher than the bank.(so they are paying themselves from the extra interest money you are paying out. Basically you are giving them "free cash" just for the convenience of not going to your bank and borrowing the money from the dealer. $100+ here and there free money - the lot is happy with that bonus cash.

Other answers are correct.

This is just one of the many tricks that car dealers use to get you on their lot, hopefully get you to fall in love with a vehicle, then take you for the proverbial 'ride'.

They wouldn't tell you how much you were 'pre-approved' for, because they probably didn't actually 'pre-approve' you for jack sh**.

Another trick is to tell you that you've 'won' some little bullsh** trinket (a little bluetooth speaker, or something) or send you a fake 'key' that you can use to see if you won a car they are giving away (the key doesn't actually do anything).

They want to get you on their turf so they can sell you something or anything before you leave.

That's just bait to lure you in. 

It's a sales trick. They got your name from a list and they'll still have to run your credit for real, this time with actual information you fill out on the application. I'll bet you weren't even car shopping at the time when they called you out of the blue to tell you the good news.

You weren't approved. You were "pre-approved." Not the same thing.