im looking for rear end and this place says he has a 91 z28 with a 5.7 and a t5, thats how he says it has 373 gears. I have been looking and i dont see any information that they even had a t5 in 91. so im looking for 373 gears, but the specs i can only find says 323 in 91 so how much better is 323 than 277 verses 373.

 

GM never put a T5 on any 350 engine. Didn't think the tranny was strong enough to handle a 350.

Now, having said that, I've got my original 91 World Class T5 behind my 383 in my 91 Formula, so far so good. There are aftermarket T5's that are a lot stronger, too.

GM also never put 373 gears in any F-body. Highest I've heard of is the 342 in the T5's like mine (which originally was a 305).

Sounds like a pretty worked over setup to me. I'd see what shape it's all in before proceeding.

373 is more a racing gear size, highway mileage will drop a bunch due to the higher RPMs the engine will be turning. 277 was an automatic gear size, 342 was for manual tranny. 323 could probably be either but I'm not sure.


- Vern

 

Just what I thought. Thanks! I might as well salvage the rearend I have now since it was custom from the factory and all numbers are matching. Spend extra-get it right or spend a little-quick fix.

 

GM put 3.73s in plenty of F-bodies; just not any 91 ones. My 83, and most other L69 cars, came with 3.73s.

They definitely had T-5s in 91; in fact, until I put a T-56 in my 83 car, I had the T-5 out of a 91 1LE car in it. They also were available in lesser 305 TPI cars than that one, and in the base-model non-performance L03 (TBI) and 6-cyl versions.

As stated, GM never put the T-5 behind a 350; and they never put 3.73s behind a 350 either. Typically, the 350 TPI cars came with either 2.73 or 2.77 gears (10-or 9-bolt) in the non-G92 cars, or 3.23 or 3.27 (10- or 9-bolt) in the G92 cars.

But, people change stuff all the time, and it's not impossible that some car in the boneyard might happen to have that combo in it. The factory didn't build it like that but someone else might have. Gear ratios are pretty much good at face value; if it's 11 and 41, it's a 3.73, no matter what motor and trans it is.

On the other hand, buying used gears at the junkyard isn't exactly the smartest thing in the world to do, especially not if you're having to pay somebody to install them. You'll only save a very small percentage of the total cost, and you'll be taking a considerable risk. I would recommend against it, as cheap as gears are. That gear set is only about $180 new.

Rear ends don't have VINs, so there's no "numbers matching" about it. Nobody else would ever care anyway.

 

All true. Good post.

 

If you eant to find out what the rear gear is you need to do a bit of work.
Put the rear on jack stands
Mark the drive shaft and one of the tires
with car in neutral turn the tire
count how many times the shaft turns in order to rotate the tire one complete time

 

If you really want to know what's in teh rear, with no guess work or uncertainy of any kind whatsoever, take off the cover and look. All of this about turns counting and "codes" and "2 stripes and "turns the same way" and all of that crap, just leads to confusion and wrong answers.

What's there, is what you find there. Go straight to the source and bypass all the detours.

Buying used gears based on counting drive shaft turns is at least one full notch in intelligence (or at least, in risk-taking) below buying used gears in the first place.

 

My mom wrote the orginal post. the plan was to just take the whole rear form the 91. I was calling around and I asked for disk breaks and posi, that appears to be a very hard combo to find, he said that he know's its a 373 posi because it has a 5.7 and a t5. I didnt think that was the best way to determin whether or not its 373.

Randy's ring and pinion has a carrer for the 9bolt posi for $999, and the gears (yukon, are they good?) only for like $160 or so, with all other parts the toltal rebuild kit for the 9bolt its $1342.67, but if i had a 10 bolt it would be about $700. only problem is im sure I wouldnt be able to find a 10bolt with disk breaks and 3:73's, so if anyone knows a better price on the carrer for a 9bolt it would be great help.

Is it even worth it, will it just break again?. The 277 in there now only broke because it ran out of fluid, it started grinding, put fluid in it and it still broke. If I stomp on the new 3:73's every once in awhile is it going to break fast or should I get some life out of it?Ive never had rear end trouble before.

 

What new 3.73s?

The 9-bolt you have is so expensive to repair, and such a dog of a rear to be putting money into in the first place, that I think you'll do better to just replace it.

There are so few rears that you'll find in junkyards with 3.73s, posi, & disc brakes, it isn't worth trying to find that combination. And even if you do, it will most likely be a 84 10-bolt with a Gov-lock and Saginaw calipers. Yuck.

Your best bet to come as close as possible to that combo is probably going to be to locate either a 9-bolt from 89 ONLY with 3.45 gears and the PBR brakes; or a 10-bolt from 90-up, with the PBR brakes, and put your own 3.73s and posi in it.

As far as what you're likely to be able to come up with easily, you should be able to come up with a 9-bolt with 3.27s and disc brakes, without too much searching; they'll most likely be the same crappy Saginaw calipers you have now, which will make it as near a direct bolt-in as possible. All you'd need to change is your speedo gears.

As far as predicting how likely another rear is to break, that all depends on how you take care of it. Some people can break an anvil with a rubber mallet; and some are just the opposite. The things that tear up a rear (besides running dry!!) are hard launches especially with slicks, and one-wheel-peel, and speed shifting a manual transmiassion.

Just FYI, I built the rear for my car that's in it now. It's a 91-92 housing, with PBR brakes; LCA lowering brackets; an Eaton heavy-duty posi; 3.73 gears; crush sleeve eliminator; main cap studs; and a brace girdle cover. That's pretty close to as maxed out as you can max out one of the stock rears for these cars. You're not going to find one like that in the boneyard I wouldn't think.

 

Converting a 10 bolt drum rear to discs is cheap and easy. If you are interested in an 87 9 bolt 3.27 gears and disc brakes I have one.

 

Problem is money

I found the entire gear and carrer kit for the 9 bolt 3.73 for 895$
that way I could keep my disk breaks. It seems I could get a 10 bolt, but I would still have to spend money putting 3.73s in it and would be hard to keep the disk breaks.

 

If you are looking at spending that kind of cash buy a used 10 bolt and rebuild it. Gears are like 200, used zexel torsen take off is 100. you can easily find a disk brake 10 bolt for less than the remaining 595.

 

AFAIK the used Zexel take-offs are long since all gone, unfortunately.... I'd strongly recommend calling SLP and making sure you can actually get one, before assuming you can take that course of action.

 

After hunting around for my own 9 bolt stuff the last few years, I would recommend that you hit the Thirdgen classifieds and look for a used 3.27 posi/gear combo instead of spending $900 on a new one.

I could be wrong, but I didn't see you post specs on your engine combo that would warrant a 3.73 posi rear.

It also seems that you are a bit young...which is fine...but don't get yourself set on a particular part, like a 3.73 posi, without taking into account the rest of your engine combo.

If you have a stockish TPI setup, with a T-5...keep the 3.27 or equivalent for mileage...it will be decent enough performance with a 5 speed.

 

My factory 305HO (TPI w/dual cats) had a 3.42 posi from the factory. I'm still using that with my 383 SuperRam setup. If this is going to be a daily driver you're trying to put together, I'd suggest following 88TPI406GTA's advice and either use a 3.27 or a 3.42.

A 3.73 is pretty much getting into the drag racing only territory with a T-5.

A 3.73 would probably be fine with a T-56 due to it's lower overdrive gear ratio, but it gonna kill you on mileage with a T-5.

Just my two cents....



- Ye Old Phat Phart, Vern

 

I should also note that my suggestion is in the context of keeping your existing 9 bolt as well.

If you want to look into swapping to a 10 bolt, that is an option, but not the simpler one, IMHO...

If it were me, it would depend on if you have any $$$ into the rear brake parts recently or not.

 

Yeah--my 3.73's with a T5 and dead stock 305 are just a bit low. It cruises 70 mph (I guess, speedo isn't hooked up yet) at about 2400 rpm, gets about 24 mpg (I think). I bought the car with the 3.73's and the original '82 automatic and drove it from Tallahasse to West Texas at 60 mph--what a drag--but now with the T5 it's acceptable.
If I could, and had unlimited cash, I'd go for the 3.23's to use the midrange better. From light to light though, the 3.73's pull really strong, even with the 305, and I'd probably miss that little chirp in second when the secondaries open. The motor seems to hit a sweet spot cruising at 2500, sort of lazes along below that, and pulls up to 4000 rpm easily in 5th--I have no idea how fast that is but neither I nor the car want to go faster without a cage.

 

Can you not get a T-5 built with a really small (numerically) 5th gear for the highway?

The 3.73 I just installed seem to be fine behind my 700-R4 on the highway, but I've been planning a T-5 swap for a couple of years now and was probably going to do it over the winter...do I really need to be looking at a T-56? Seems like a much more complicated and expensive swap....

 

Well, I looked very carefully into the T56 v. T5 business last spring; then Chevy High Performance had an article on just this about March or April--they said the T56 is basically an emissions tranny to bring a large displacement motor down to low rpm to pass smog regulations, which you can do with EFI, but the T56 weighs 30 lbs more, requires a bunch of propreitary clutch stuff and reverse lockout, and to use 6th in a mildly built small block without EFI you need at least a 4.10 rear end.
Tom at TKOPerformance quoted $700 to upgrade my T5 to take 450 hp, including a standard rebuild.
My complete swap from an automatic to T5 cost under $1000 including a light flywheel and it's solid, looks factory original, and everything lined up the first time--no headaches. My advantage was that I found a cheap parts car.

 

rbjones - What gears are you running?
I'm encouraged to hear a success story on a T-5 swap, and the price is sure right..

Is anyone running a stock T-5 with 3.73's, and if so, what RPM's are you turning @60MPH?

 

Ka-Z-Canuck; Yup, I'm running a dead stock Quadrajet '82 305 in my '82 Camaro with a dead stock '91 WC T5 and Torsen 3.73 posi, Moser axles, and it's just fine. I ended up with this combination because my brother, who is much more of a drag racer than me, moved to Florida with this rust-free car after he'd done the rear end--also with the boxed arms and hard plastic bushings--and he found a rust spot on it after about six months down there. He sold it to me to get it back to a dry climate, so it had the back end set up for drag racing and the front end stock. There's a little junk yard in our town owned by a guy who likes to drink beer and a friend of mine told me he had a stick shift Camaro that had just come in--I went right over there and he was sitting in his pickup hoping for beer money, and sold me the whole car, minus the engine and radiator for $200. It's a '91 RS and had the 26 spline T5.
I bought a GM nodular iron 11.4" 15 lb. flywheel new for $169, matching clutch set for about $200, new pedal pads, new slave cylinder, clutch fork and pivot, needle bearing pilot bushing, and that's about it. Did a bunch of cleaning and painting--local upholstery shop made a new shift boot for $10--repainted the ash tray so it looks like it's never been smoked in.
The plan was to build a 4-bolt 350 I have in the barn--but--this thing runs so well and is such a clean, original '82 that I don't want to mess with it. I put in the 3" HO exhaust back to a 40 series Flowmaster with dual 2.5" exits and with that light flywheel it sounds almost like a DZ 302. This thing is all GM, was extremely easy to put together, sounds great, dependable and gets good mileage on 87 octane.
There was deep confusion at one point because '82 Camaros had mechanical linkage but guys on this website guided me through cutting the hole in the firewall and reinforcing the pedals and now it looks dead original stock. I lucked out getting the parts car so cheap and the tranny being in good shape. The T5 has a tall overdrive--drops about 1200 rpm from 4th to 5th (from 3000 to 1800 rpm). I heard there were three gear sets in the T5's of those years, one with the tall 5th, and I guess I got it.
If I were ever gonna go with the 350 I'd build it to match the 3.73's. If I were choosing gears to match the stock 305 with the T5 I'd go with 3.42's--but now that I have the 3.73's I really like them.
I would guess that cruising at 60 mph it's doing maybe 1900-2000 rpm, getting 25 mpg.

 

Thanks for the post...that was a great bit of luck getting the parts car that cheap. Because I will be paying for the labour to get this done, I think I will spend the money to get a rebuilt T-5. But it's nice to know it won't be to racical a combination.

 

Cra-Z-Canuck--somebody has a '91 or '92 T5 rebuilt in the classifieds of this website for $500, I think, another for $375. If you're gonna have one rebuilt I'd recommend you contact Tom at TKOPerformance and have them put in some of the forged steel parts they have--they also recommend an aftermarket shifter. My shifter is stock and does just fine but I see how it could be better.

 

After just dropping $1600 on my rear end, I probably won't be looking at the trans for a few months, but I'll be sure to check the classifieds when I do....That's interesting about the 3 different gear sets in the T-5, is there a way to tell which ones are in there? Can you swap out the 5th gear easily and put in the low one?

 

Well, some of the members of this board say they have bins full of T5 parts. Maybe if you post a new subject like T5 parts wanted or how to rebuild one they will answer. The cases on the WC T5 are all the same, they say, so any gear set will go in there.
One very popular place, I don't remember the name, wants as much to rebuild a T5 to 600 hp capability as it takes to buy a Tremec--$1500 to $2000 USD.
The rear end in my car cost around $2000 altogether--I know what you mean--but that's money well spent for a bulletproof setup. I'd recommend you contact Tom at TKOPerformance--he's a member of this website, has fair prices and knows his stuff as to ratios and strength. When I go with the 350 I'll send him my T5 for an upgrade--some time.

 

I did a google search for "TKO Performance" and it came up with a Corvette site? Do you have any contact info?

 

Yeah, I've had that problem, too. One of the first listings at the head of this category is common questions on the T5/T56 swap and it's hosted by TKOPerformance--maybe that's it. The company that gave me the good information and quote is in Delaware, a guy named Tom, and I still have his pm to me from last May but I haven't been able to get the reply function to work--no computer whiz. I'll look around again and see if I can dig him up.

 

91formulaSS--yup, that's him; second listing in this category, helpful/useful T56 information--click on TKOPerformance in the column on the right and you can send him a personal message. Note that there's no space between TKO and Performance.

 

Whoops, wrong thread.

 

I was also trying to find tkoperformance and have thus far only been able to find the corvette site and the tremec site

 

OK--check it out: under this topic we're in right here, "transmissions and drivetrain," the second thread listed is "helpful information, frequently asked questions about T56 swap." When you see it, follow it across to the column on the far right and you'll see "TKOPerformance." Click on "TKOPerformance" and you'll get a box to send a personal message to them in Delaware, not the Corvette site. That should work--I hope.

 

Found TKOPerformance's e-mail address: BigRedK5Blazer@aol.com Using this, you should get Tom at his shop in Delaware.