1999 GP Replacement Parts Selection Questions

For the most part, we all have daily drivers that don't use a Pontiac V8. Just doing my homework before I proceed with some purchases. If you don't know/care anything about front wheel drive cars, go ahead and pass over this post. Looking for specific rather than general info. Thanks.

I drive my junker 1999 Pontiac Grand Prix GT coupe twenty miles twice a day with dozens of stoplights and speeds below 60 mph. It has the naturally aspirated L36 231 CID engine and the 4T65-E trans. I installed Dorman's redesigned upper intake manifold and had the trans rebuilt with new stock differential, gears and all, at around 120 thousand miles. Recently I installed a 2.5" aftermarket downpipe with hi-flow cat and I run an O2 emulator with no problems.

I have 170 thousand miles on it now, and of course repairs are snowballing quickly at this point.

But somebody ran into me a few weeks ago. Didn't hurt the driveability at all. After much looking around, I've decided to keep and restore it because I truly enjoy driving it. Its a loaded luxury coupe with satisfying performance and outstanding efficiency, very comfortable year-round in all weather, city or highway. Just what I want. The plan is to achieve tip-top mechanical condition aside from an engine rebuild (runs great), then fix the wreck, maybe.

Here are the questions. Hopefully some of you "do it every day" mechanics (Hi Steve, Wayne, Stillwell, anyone else?) can assist me with choices on a few replacement parts. The 3800 forums seem to be all about performance upgrades and I'm just maintaining a stocker and want my repairs to last. These are just the items I am considering but needing input on- thanks in advance for any solid input you can offer from your own repair experiences.

LOWER INTAKE GASKET-

Comes from FelPro or GM now in an aluminum-framed version, as opposed to the leaky plastic first design. GM's current offering is $64.48 list, $45.20 online. Can't tell if thats the plastic or aluminum. FelPro aluminum is $75, plastic is $49. The car has iron heads, an aluminum lower intake and a plastic upper plenum, stock. Mine is leaking again now under the UIM, and I have the Dorman-specific gasket set. What would you use?

EGR VALVE-

Mine isn't bad yet, as far as I know. GM is $333.88 list, $205.34 online + 5 for the gasket. Borg Warner is $160 plus requires a $50 pigtail. House brand is $150, direct fit. What would you use?

FRONT STRUT MOUNTS WITH BEARING-

GM $157.21 list, $110.22 online. Moog $149.99, KYB $40, House brand $34. Which would you use?

FRONT STRUT AND SPRING ASSEMBLY-

KYB OE spec $190. Monroe EconoMatic $136.99. Monroe QuickStrut $216.99.

I kind of like SensaTrac Monroe shocks. Struts only in that are $85 each. Would my springs still be any good at 170K?

WHEEL BEARING / HUB ASSEMBLY, FRONT-

I have had trouble with cheapos, want the best there is but dang.

GM $476.32 list, 292.94 online. Precision brand $125. House brand is $90 and they suck, Precision is OK. Which would you use?

FUEL PUMP-

GM $481 list, 295.83 online. Precision or AirTex $252, both require connector swap (part included). Delphi OE spec is $317.99. Which would you use? Mine still works.

OTHER-

How often should I change ATF and filter? Preferred filter / fluid? Got 50K on the rebuild.

Anybody tried a shift reprogramming kit in one of these? Its a simple spring swap deal, no computer mod required. Wondering if it might extend trans life.

THANKS-

I'm more of a four barrel glass packs and HEI person and I've done more body repair than mechanical on these newer cars. This place seems to have plenty of mechanical knowledge on hand, so I thought I would pick some brains. Mine is smoking from all the options. Big differences on some parts. Can you help? Thanks again.  

I am aware that I may be able to find better prices but I am mostly looking for feedback on quality.

Here are the references I am using:

www.oreillyauto.com


www.newgmparts.com  

Looks like its the buy-and-try method for me then. Thanks for the email, wayne.

Just add this post to the blooper reel.  

whats up junkman! naw this aint no blooper!

  hey I have had major computer issues the last couple of weeks on top of working a lot and  working in the shop on mine and my brothers  old junk and a few side jobs.  
 Im gonna make a thread of GM tilt steering column tear down and rebuild.  Me and bro did one in the black truck it got the royal treatment so it should lay down a good thread I hope

 Ok My advice with your GP, Ill just go in order as you asked.

EGR valve: if yours is still good, leave that original GM on there until it dies!!  they rarely go bad,  when they do your car will act like it basically has a terrible vacuum leak.  The worst it can do is stick open and that is what causes the poor running.

front struts and springs: as long as those factory springs are holding the car at ride height?  let em eat unless your wanting an upgrade and im not getting that vibe.  

I have used gabriel and monroe gas shocks and liked em both so which ever is close and lighter on the wallet and you should be good.  Yes replace the upper strut bearings and bushings while yours are out (moog)  is a pretty good name I have used several of their pieces and they appear to be quality for the money.

 Oh and check them tierods real good inner and outer usually the inners are ok and the outers only wear out.
 ((((((((any strut work will require a front end alignment so replace everything your gonna while its torn down)))))))))).

front wheel bearings:  GM is perdy darn good chit prolly best! but I think autozone timken is pretty close.  all else is indeed crap.

fuel pump:  leave it alone, the GM is rock solid.  if it ever gets hard to crank or surges on a full throttle run, thats it talking to ya and then get ready for replacement.

trans fluid:  pull the stick and wipe it on a white papar towel if it nice and pink, and has a normal smell, leave it alone.
 if it smells burnt and kind of an onion funk then its time for a change. if you do change it. only use the metal rubber coated gasket.  I usually keep the factory one and only change the filter
I like ATP filters most of them are metal screens only these days and changing the filter usually aint necessary.
 If the dipstick has a gunpowder type residue then its time to pull and clean the pan, it will show up on the paper towel.
  if for some reason its really dirty (50k is not high miles on a 'cars' trans fluid)   then just drain and refill on the next couple of oil changes to clear up the fluid then id say install a new filter.

 dont get suckered into one of those $100 "t tech" units at the local oil and quick lube that circulate  a couple of qts of fresh fluid into the trans! pure waste, a couple of fluid changes will clear it up and do the same thing.

shift reprogram,,, is yours shifting sluggish?  is it cable operated like the older units?   if so I would check to make sure the cable is fully extended at WOT  yours could be stretched a couple thousands and may need snugged up.

and if your still using dexcool,,,,,,,,,,, it needs to be changed about every 50 to 60K to be on the safe side.

thats all I can think of at the moment.  

Chevelle! Thanks for stopping in, man. Didn't know if I was hexed or what, just needed a little advice / discussion with a rego car fixin guy. Still learning FWD & EFI. Again, thanks this is just what I needed, plain car talk.

A column teardown and fix picture post sure might help some folks. I hit my turn signal lever (in the OLD GP) too hard once (oops) and I think I cracked a plastic piece inside there. Still works, but resists when trying to switch on the signal with the wheel turned sometimes. I'm just gentle with it, been that way for years. What y'all doing to that one when you tackle it?

EGR valve- I think you're right, I'll ride whats on it. Starting to show it's age visually, and its an important piece concerning MPG. Wayne's advice was to use an advanced scan tool and confirm that it can open and close 100% by "manually" controlling the valve and watching the percentage on the tool. Could clear up a lightly stuck one, too. No problem yet on that, doing nothing now but would probably buy the MasterPro when it craps.

Outer tie rod ends are already greasable MOOGs, thats one of the first things I did. I should check ball joints at this point, bushings are fine. New control arms might not be needed till a quarter million miles or so!

Struts- I think I'll leave the springs, the ride height is fine. Much cheaper that way but then I need the big strut tool. May just remove em and have a front end shop do the spring swap. Kinda leaning towards the KYB stock-type and using KYB mounts. Or Sensa-Trac struts and MasterPro mounts.

I still can't figure out why the MOOG mounts are so dang high? Not a pair. They are an important wear part, and I think my other buddy swears by the MOOG mounts. Wish I had both in hand to compare. Maybe thats one item I'll need to visually compare at the store, to make my decision.

The wheel bearings ... agreed. But man I just don't know if I can see my way clear to pay what GM is asking. I gotta call the dealer anyway so I'll double check that price. And see about Timkens from AZ, at least thats a brand I've heard of.

Fuel pump must be OK. For some reason I pause before cranking just to listen to it. Still quiet and prompt. Filter new (WIX), old one may have been original because it was awful dirty. Need me a new vacuum pipe assembly for the fuel reg, I had to make one out of modulator pipe and plug boots and its not pretty, lol.

O'Reilly's only stocks one brand of transaxle filter now, not ATP. Thats what I want to find. Trans health appears to be great, tiny gunpowder amount on tip of dipstick. I did ask the shop that rebuilt it, how much for a fluid and filter change and they said $150. I didn't let my eyes bug out like Daffy Duck, just spun on my heel and said "I believe I'll do that one myself!".

My 4T65-E works perfect, 5,800 every time, at WOT. Its a busy little box in traffic. It uses a shift cable and "range switch" and the throttle is a cable but the kickdown is electronic I believe. The shifts feel like perfect little clutch stabs but I'm used to TH400 thumps so I thought I'd ask about the shift kits in case anyone had feedback. HPP used to mess with these cars.

I do use orange Prestone (Dex copy) still, never had a good opportunity to flush it out so I used it. Had enough leftovers from the manifold job, to also do the radiator replacement last weekend. So I still use orange, but its bleeding from the intake again so I gotta go in soon. If I ever do a heater core, thats probably when I'll go green. Its just such a pain flushing out all the old. At least it don't hold much.

Anyhow, thanks again Brandon. Hows the hot rod doin? I really need to work on the 455.  

I just read up on the GP problem, and posted there.

 Coolant from the intake gaskets is  very routine in these year models V6 and V8 engines GM products.

Have you already replaced the intake gaskets before?  Fortunately they usually leak out the front or rear.



Rarely when the plastic gasket cracks they can leak water inside the engine! so I recomment replacing the intake gaskets asap.  Iv done a few and my best friend was my inch pound torque wrence with all the tiny bolts.  

 Be extra careful with those (Popeye) arms of yours, a 1/4 drive metric socket set will do dang near the whole job.

On the ole gp is it straight or tilt?  the old straight columns are so easy to work on I could dang near do it in my sleep!  all you need is a lock plate tool (cheap from part store) and in about an hour or so you could be signaling with confidence and not acting like its fittna break off LOL.

OK your trans sounds good, a fluid swap to keep it fresh with detergents and you should be good to go.  There is indeed nothing like the punchy shift of a TH400 trans! both of my duallys have them and it makes them a joy to drive with the confident trans under the hump!
 Im sure there is probably a 2-4 servo upgrade somewhere, it may even be the same as a 700r?  ive never checked on such.  Your description tells me to let er eat tho



Oh and you can rent the strut tool from azone or advance and return for a refund.   shop will prolly charge you $20 just to use a press.   have you ever installed new struts before?  

I did the lower intake gasket before, used a Fel-Pro plastic for that and swapped the upper intake to the redesigned Dorman which uses a specific gasket. Got that, and just picked up the GM aluminum framed lower intake set. Mine is leaking now at the rear end mainly, barely in front. Hope my EGR pipe stayed put when I swapped upper intakes and drove in the new Dorman pipe, to the lower intake. I'll find out! Ordered a GM + cable and a fuel reg / evap vacuum harness while I was at the gettin place. GM doesn't offer aluminum coolant elbows yet but they are available aftermarket. I'll use my old GMs if they don't break, Dormans suck.

I picked up a new tiny torque wrench, borrowed last time. Those things are cute, lol. Gonna re-use the bolts. The specs are not much more than finger tight. I'm hoping the spec on the LIM bolts is same with the different gasket.  

Old 69 GP is straight column and column shift. Got a '72 buckets and console car though, with tilt. Hell even the dash is different on console models. But I wanted the seats and factory rachet shifter, for future use. Its a #s match tan plain 400 car, hoping with virgin block. Not too concerned about the turn signal nuisance, but yeah its just a lock plate tool away from fixin if I don't ditch my column.

I do love the TH400 bang but they sure gobble power. Wouldn't want my half shafts to be subjected to anything too harsh. Think I'll do like you said, just change my filter and get some fresh fluid in, then let er eat. She likes Acura flavor.

I've always just changed strut assemblies on wrecks. Never my own. Usually had a mech tech do the front end work after the crash is fixed. Seen struts come back put together wrong and such. Prolly call a buddy or two and see who has what then go from there.

GM wants 157.21 each for front strut mounts and 380.60 for a hub. Not today! Man I got a lot of work to do. Better hurry or they will both be broke at once! Thanks again for the good ole boy advice, man. I think about stuff too much, and that input helps me decide things. Great because I just don't have much time or energy to spend wrenching.  

I just got back from loafing around with the family in the big family dually

I love bucket seats, though I never had a problem with a good column shift, I would only swap in the column simply for the tilt, going to floor shift would simply be an extra.

 Rekon why it seems that our own driver cars seem to be the most difficult cars to work on???????  Man I got a new motor mount that needs to be put on my beater ford focus.  Its been rolling around in the floor board for at least a month!!!
 
I dont see how GM can even sell a part for some of the prices attached to them!

 Man dont sweat the strut job, as long as your car aint rusty underneath I could do that whole swap in about 4 hours tops, without air tools.  Having to go get the alignment is prolly the biggest headache.  Around here they are $65 for front, an another $25 for rear.

Did you say the hub assemblies are already bad and need replaced?   Have you jacked the car up to see if they have any wobble?  
Yes, Dorman parts have had me cussin many times! I look that brand part over real good before I take any out of the store. I cant believe us humans will waste good earth resources to make what is basically garbage!!!
 
 You have probably already know this, but when it comes to expensive jobs that I dont want to fund all at once. Ill buy up the parts over several weeks or months, and just save all the receipts incase I had to take something back.

Even if I had the cash to cover it all, Ill just span it out to soften the wallet attack.

Your welcome, and good chatting with ye as well! ask anything anytime. if ye need to call ill shoot ye my number. sometimes all the typing can be exhausting.  

Tried to PM you, the forum was acting wierd again and doing the double post thing and refreshing to an older version of the page. Let me know if you got it or not.

Already put on front hubs, cheapos. Need to re-check them. Right rear has a decent parts store one on it, left rear is original and maybe loose/noisy now. That or the tire I had patched has gotten noisy, its on that corner.

You're right about that wallet hit. For me its more like a time off hit, because I work full time and I'm using wreck money to fund my mini-resto on this car. Need to go see my fam too but it looks like I'll be wrenching to keep myself out of hot water this weekend! The gang probably needs a break from all my posting   and I need the practice!

Y'all have a peaceful weekend, I'll try to work through all this now.  

I won round one.    Ding-ding!

Yesterday I installed FelPro valve cover gaskets, GM lower intake manifold gasket, Dorman upper intake plenum gasket, GM coolant elbows and fuel reg vac harness, and new lower injector o-rings. Did not install the supplied PCV valve or thermostat because my existing are still good and they can go in anytime so I'll just have spares. Also picked up my GM + bat cable and ordered another vacuum line. It was eating a slow steady flow of coolant and everything was nasty. Acura dude said it was puffing when I stomp it and now that should be gone. Plus it was leaking to the outside, coolant from the plenum gasket and oil from the lower manifold end and then oil from the front valve cover. There have been a couple occasions when it ate some unfiltered air from the big rubber intake hose not being on good, and when I bought it the wrong (smaller) air filter had been installed by an oil changer. With all that plus the coolant / oil fog floating around in the plenum, my throttle body was caked. It was even beginning to stick shut a little, on the first pedal press of each day. Runs like it ought to now. Last time I changed injector O-rings I cracked one of the plastic injector tip shrouds and a chunk broke off this time. I'm not too worried about that, it doesn't affect the function but I'm not so sure it will stay put so I'll probably get another injector. I'll keep an eye on it this week and plan for stage two.  

Heres the 3800 guts, if you want to look:



The plenum with removeable runners, good for cleaning!



Bottom of the lower intake:



Top:



All happy again, and much cleaner!    My hands sure are dirty!

Thanks to Rob for the pizza and for calling out the torque pattern. I'll rest today and go again next weekend.

 

looks good!  

 Better be glad it dont have the 3.1 engine those things have the pushrods going through the intake!  and the rocker arm bolts are easy to pull the threads out of the head!! Happened on my dads alero.

Did ye change them back spark plugs while you had it down.  I always do on customer cars if they aint just been changed.  

Yeah I did plugs and wires not that long ago. Delco Iridium, I may try NGK next time. Helps access if you take the dog bones loose and rock the engine forward first.

My Dad had a Celebrity wagon with that 3.1, never had to work on it though but it had decent pep. That engine is probably just a different set of problems. Later 3800s have aluminum upper intakes.

I figure as always, I can't call this a good fix until I have a couple days on it. That cooling system took a long time to purge this time (air bleeder on therm. housing), it always takes two or three heat cycles to get it full of coolant. Don't see any leaks yet and she sounds pretty happy for now ...  

ah yes the ole bleeder valve.  I wonder how many folks have damaged engines trying to fill them with coolant and never noticed the bleeder valve!!!  

Matt, sorry I missed this thread somehow but I agree with all the advice the others have given. My only comment about the struts is to carefully compare the cost of the complete assemblies vs buying the struts/bearings/mounts separately and the added time/cost of getting the spring changed out. Other than that, if it has been eating coolant you may need to consider replacing the o2 sensors since they degrade when exposed to coolant residue and that causes mileage woes due to an incoorect air/fuel ratio.
Steve  
A little help... 'cause we don't all have to learn the hard way!

I was checking her for leaks after today's drive. That bleeder gets coolant all down the back of the engine so its hard to tell exactly whats what but I did see a little coolant still on the intake. Soaked it up with a rag so I can re-check tomorrow. If its a leak, it probably just needing more thread sealer on the back bolt.

The idle is smoother. Reset the MPG computer today and it was in the high twenties until I got into traffic. Usually settles in around 22. A green Integra with red wheels actually tried me at two stoplights on the way home. He learned something.

Steve, better late than never! Thanks for droppin' in. I ain't done, still playing catch-up. What I thought was my driver's strut mount clunking was the core support brace against the airbox, a rubber piece is missing. I stuffed a coil pad from a HEI in there to stop the noise, so maybe I don't need mounts yet. I know if I ever want my front OR rear alignment to be within spec, I need to start with struts and that means yep, doing it all at once to save. Until tire wear becomes an issue I'll just keep replacing whatevers noisy or bleeding.

Thanks for reminding me about the O2. Got a favorite brand? Rear one is just a hole plug but the front could be nasty now. Thats the expensive and important one that "adjusts the carb" on the fly. The other one is just a yes or no "is the cat home?" asker. I'm sure the front one is past it's prime but the OBD still gives it a pass. Thats probably the biggest difference between my GP and the rest ... I keep that check engine light OFF!