1975 L-48 4 speed radiator

[Lynn S.]

The supposed original radiator in my '75 - L48 motor car with Manual trans has ports on the inlet/outlet tank to accommodate automatic trans cooling lines. Did Manual trans car radiator tanks also come with these ports or were these only on automatic trans cars? Thanks for everyone's advice.

[Joe L.]

Re: 1975 L-48 4 speed radiator

The supposed original radiator in my '75 - L48 motor car with Manual trans has ports on the inlet/outlet tank to accommodate automatic trans cooling lines. Did Manual trans car radiator tanks also come with these ports or were these only on automatic trans cars? Thanks for everyone's advice.

Lynn------


In general, PRODUCTION radiators are specific for manual and auto trans applications----auto trans applications with oil cooler and manual trans without. In SERVICE, if the radiator without oil cooler is ever available, it is usually rather quickly discontinued and replaced by the with oil cooler radiator. In other words, in PRODUCTION GM wants to save the extra cost of the oil cooler for manual trans applications which don't require it. However, in SERVICE, things change. Then, they want to consolidate part numbers and the buyer just has to bear the extra cost of the oil cooler in the price of the SERVICE part.

For 1975, I think that this MAY have changed. I think that for 1975 the 3 different radiators used for 1974 MAY have been consolidated into one----the GM #3030684 which included a transmission oil cooler. If your radiator has a tag on it you might check it for part number, broadcast code and, especially, date. That might help determine if it's original to the car. Also, keep in mind that even if there were oil cooler and non-oil cooler radiators used for 1975, the factory could have easily substituted an oil cooler radiator for the non-oil cooler version for cars with manual transmission.

[Tom R.]

Re: 1975 L-48 4 speed radiator

Lynn
In addition to what Joe, posted our study that is included in the 3rd edition of the 75-77 TIMJG is the following:

All radiators are copper, painted gloss black. By 1975, radiator applications are consolidated into a single assembly used for all transmission installations. Outwardly, they are identical except the use of transmission fluid cooling lines on cars equipped with automatic transmissions. See Table 19 on the next page for radiator application, broadcast code and GM usage.

Heavy-duty defines the difference rather than transmission. So both A/C and the ZN1 (76-77) calls out the heavy-duty radiator. GTM# 3030684 was the base radiator...non A/C with broadcast code ME. if You have a buildsheet, check the radiator box where it calls out the code.

[Brad Hillhouse (37766)]

Re: 1975 L-48 4 speed radiator

Lynn can you please post several photos of the radiator you have? That may help us identify it is an original or not.

thank you

Brad Hillhouse

[Lynn S.]

Re: 1975 L-48 4 speed radiator

Thanks guys for your guidance. Unfortunately no build sheet. But we can move forward again with this info.

[Patrick H.]

Re: 1975 L-48 4 speed radiator

Lynn
In addition to what Joe, posted our study that is included in the 3rd edition of the 75-77 TIMJG is the following:


Heavy-duty defines the difference rather than transmission. So both A/C and the ZN1 (76-77) calls out the heavy-duty radiator. GTM# 3030684 was the base radiator...non A/C with broadcast code ME. if You have a buildsheet, check the radiator box where it calls out the code.

Tom,

Do the radiators from 75 onward have the typical square and rectangular cutouts on the upper and lower support bars, as in earlier years?

Patrick

[Tom R.]

Re: 1975 L-48 4 speed radiator

Patrick
Those we looked at did but we also see the greater use of the black foam shrouds in 76 with the transition of the 75 cowl induction to the ThermAC air cleaner system. Meaning gaps between hood and surround were better covered up