69 Impala, several upgrade questions...

[gsteffens]

Well I've been away from the forum for a while due to a multitude of reasons, but I'm getting back to wrenching at home and I've come to some questions.

Some of you may recall us bringing our 69 Impala up to the Dyno Day in Plainfield. Well after that I took the front of the car apart and she has sat apart since then. I took the hood, core support, fenders... etc... all to primarily repair the fenders and rebuild the suspension.

I recently had a friend of a friend install the fender patches, and all that will be needed on them will be the bodywork/touch up and paint (once installed). Much still remains on the suspension.

But I now come to the mechanical things. I never plan for this to be an all out drag car. But in light of not ever having intentions to fully 'restore' the car to OEM, I want to make it have a little more reward to the butt dyno.

I am going to take it over to the Exhaust Works in Montgomery and have him put a set of long tube headers on and mate it to the existing exhaust, which I think will wake it up a bit, being a good 'ol 350 small block.

I also want to install a shift kit in the transmission, and put a bigger gear in the differential along with a limited slip upgrade.

For the transmission... this is a TH350 three speed automatic. I do not want an all out race setup. I would like it to behave somewhat normal under gentle driving, maybe with a little firmer shift. Is it possible to have this AND also when I go WOT, to get a kick/tire chirp with the 1-2 shift?

For the differential... I know it is the 12 bolt, and that is about it. I am not sure of which gear it has, but I believe it to be a 2.XX because 1st gear goes forever and in 3rd it cruises at 1800 rpm at 55mph(approx, with no locking TC). I want to replace it with a 3.55, and a limited slip. Are there any recommendations for a "plug and play" limited slip... as in, install and go? Fuel economy change is not even going to be an issue. It loves gas as it is, and is going to be a weekend fun car for the rest of its days. So a mpg or two drop will be fine.

I will be taking a class in which we service differentials where I plan to pick up the skills to do the swap myself. I also have about four neighbors who could help if I needed it (all hot rodders.)

Any advice to all I mentioned is welcome. Hope everyone has been doing great since I've been gone. Thanks!!!

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[gsteffens]

I was reading up on the B&M kit for the trans set to strip mode, it seems to be what I'm looking for in that respect. Any ideas? How about the other stuff?

 

[Runtz52]

i would go with a B&M kit. being that it is an impala im assuming it is a column shift auto and not on the floor. i know B&M makes a manual valve body that also retains factory shift points when placed in D on the selector but also give the option of manually shifting the gears like u would in a stick car, but i dont know if that is what u would want assuming it is a column shift, as for the rear end a 3.55 should do nicely, but as for companies to look at i have no idea.

 

[gsteffens]

Yeah it is column shift, and we don't need the manual shift option. I just want it to shift firmer but only really "hit" and "chirp" under WOT... so as to either "heavy duty" or "street strip" mode I'm not sure.

Thanks for the input. It'll never be a 10 second car, but I'm hoping to wake it up a bit.

 

[Runtz52]

Yeah it is column shift, and we don't need the manual shift option. I just want it to shift firmer but only really "hit" and "chirp" under WOT... so as to either "heavy duty" or "street strip" mode I'm not sure.

Thanks for the input. It'll never be a 10 second car, but I'm hoping to wake it up a bit.

i would say street strip, because ur trans is controlled by fluid pressure, so it shouldnt shift hard under normal conditions, and then bang under WOT. and im tryin to do the same thing with my car

 

[Oreif]

If the diff is a standard GM 12-bolt for a 1969 vehicle, You can buy the performance LSD from drivetrain outlet. It's made by Eaton to fit the 1965-1971 GM 12-bolt rears. You can pick any gear ratio from 3.07 thru 3.73.

http://www.drivetrainoutlet.com/Loc..._Posi_Limited_Slip_1965_1971_GM_3_series.html

 

[gsteffens]

Thanks guys! I had a guy at my work tell me not to do street/strip because it would shift to hard. I was reading the descriptions on B&M's website and they said the heavy duty was just for a vehicle hauling a lot of weight that wanted a more positive shift, and street/strip was for a performance shift. I think street/strip would be good.

The car has a small transmission cooler mounted on the radiator.... would it be a good idea to get a larger cooler while I am doing this?

And to Oreif, thank you for the differential information. I know almost nothing when it comes to researching this type of changes, so that helps a lot. I am taking a class now where we will learn how to overhaul differentials, so I'm hoping to learn enough to tackle the swap myself at home with no time constraints (afterall the car does not need to be done at a certain time.)

Thanks much !!!!

 

[gsteffens]

If the diff is a standard GM 12-bolt for a 1969 vehicle, You can buy the performance LSD from drivetrain outlet. It's made by Eaton to fit the 1965-1971 GM 12-bolt rears. You can pick any gear ratio from 3.07 thru 3.73.

http://www.drivetrainoutlet.com/Loc..._Posi_Limited_Slip_1965_1971_GM_3_series.html

Is $600 or so what I will expect to pay for that LSD setup? Are there any less expensive suppliers? Is that the only type to run, or the best? Seems a bit pricey, but then again I don't know a whole lot about these.

 

[HILROD]

The rear diff is probably an 8.2 10 bolt. with a posi unit upgrade and gears it will hold up pretty good. A bolt in 12 bolt if you could find it would be better but way more pricy. The B+M kit if installed street and strip will shift nice and hard under full throttle but soft under part throttle. The towing mode will shift harder part throttle but weak full throttle.

 

[Runtz52]

i would get a bigger trans cooler, heat is what destroys an auto trans. so id a get a decent sized cooler

 

[gsteffens]

The rear diff is probably an 8.2 10 bolt. with a posi unit upgrade and gears it will hold up pretty good. A bolt in 12 bolt if you could find it would be better but way more pricy. The B+M kit if installed street and strip will shift nice and hard under full throttle but soft under part throttle. The towing mode will shift harder part throttle but weak full throttle.

I laid under there and counted it out. 12 bolts for sure. Seems like a strong rear end to me. This is a good thing right?

As for the B&M kit... it's settled. Street/strip mode it is!! I can't wait to get it now.

i would get a bigger trans cooler, heat is what destroys an auto trans. so id a get a decent sized cooler

Thanks for backin me up on that. I will add that to the list.

EDIT: I looked on Summit racing's website. There are a ton of different sizes. Any idea how to pick one?