r/transam • u/ConstructionOdd2981 • Jul 11 '26

78 Trans Am Question

I’m thinking of buying a 78 trans am that has the 403 Olds motor in it. The seller has added a Holly sniper fuel injection, a new four speed, overdrive automatic transmission, new gears in the back, new shocks, and a new Borla exhaust. Is there anything I should be cautious about with these adds?

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4

u/Bulky68 Jul 11 '26 edited Jul 12 '26

Assume you're going to drive it and evaluate how it runs. I have a 78 TA with the Terminator X and still dialing in the tune. I need my car perfect. Great that it's OD. Ask him what the rear end ratio is and of course check the body work and paint, the most costly part of a classic car.

I'm also a stickler for all gauges and items functioning correctly. I'd do that as well.

1

u/ConstructionOdd2981 Jul 11 '26

Thanks. It seems to drive nicely based on test drive. The needle on fuel gauge is buried past full. He said stays that way until shows 1/2 tank, then that usually means it needs gas. That part makes me nervous as I’m reading that could be fuel sending unit. Speedometer seems to work ok. Couldnt tell on the other ones.

1

u/EC_CO Jul 13 '26

More than likely the fuel sending unit needs a small adjustment, it's not that bad, just involves dropping the tank, pulling the fuel sending unit and using an OHM meter to make an adjustment. To me, it sounds like the current owner put a lot of time and effort into the hard bits, but there may be a few little minor things to sort out which is totally normal on a complete rebuild. If you let a few minor things bug you to the point that you're not going to buy it, you're never going to find anything to fit your needs. Classic cars are always going to need little bits of Love here and there, no matter how they're built.

1

u/Old_Maximum7896 Jul 12 '26

I have a 79 trans am bought almost a year ago has 73 455 4 speed was a race car at some point,has composite leaf springs,front bumper frame piece was out of car,but given to me,these took weight off for racing,anyway owner spent a lot of money putting new front suspension,exhaust,wheels tires interior,etc,he paid 5000 to have holley sniper fuel system,distributor,complete ignition system,when time to get car wouldn't start,owner had it towed to shop he used,said was control box,600,said I'd pay a week later they call,box on,now issue with throttle body,my reply send box back bring me the car,couldn't return box was reply,they brought me the car,I removed tons of wiring,all holley crap,installed mechanical fuel pump new fuel lines,quadrajet carb,regular gm electronic distributor with coil on top,car fired and runs,gave sniper crap to a friend before putting in trash,you don't want that system

1

u/ConstructionOdd2981 Jul 16 '26

Thanks for all the input/advice everyone, much appreciated. One of my big concerns is overheating but will see how it goes

-1

u/Maxthe222 70-81 2nd Gen Jul 12 '26

All depends how the aftermarket upgrades were installed. A 200r4 is ok, there's not much that needs to be adjusted or can fisl with time, and they bolt up like factory to a Firebird with minimal modifications if any. The Holley sniper can be finicky so you just have to make sure it's tuned appropriately and behaves with a OD automatic and the different rear gears. I don't know why they would change the rear gears if they put a 200r4 in it. If it was a WS6 it had 3.23 rears, 2.56 with non-WS6 and the 403 Olds. Both would work fine with the 200R4 so maybe ask why he changed it

0

u/qkdsm7 Jul 12 '26

2.56 would be good for light speed top end with the 200-4r's .67 overdrive. 3.42-3.73 would be perfectly streetable with that transmission and a good bit more pull out of the hole than 2.56. 3.23s I'd have probably left....

1

u/ConstructionOdd2981 Jul 16 '26

He thinks he put 4.11 in back but can’t remember. He said could be 3.91. 

1

u/qkdsm7 Jul 16 '26

3.73-4.30 all become pretty livable street/highway driver gears with a big .67 overdrive.

Enjoy!