kdirk Posted February 2, 2017 Share Posted February 2, 2017 I am facing having to do some geriatric work on my 91 coupe due to minor rust issues that I want to get under control before they progress too far. I'm needing the following: 1. Transmission cooler upper and lower hoses 2. power steering hoses to and from the cooler. Looking online I find the lower transmission cooler hose by several suppliers with different part numbers, but no upper hoses. Can't seem to get any straight answers on the powersteering hoses, so thought I'd ask if anyone here had done these recently and had part numbers to post. Kevin Link to comment Share on other sites More sharing options...
Ronnie Posted February 2, 2017 Share Posted February 2, 2017 Does the '91 model transmission have cooler hoses with special fittings or something. I thought other models just had hose clamps holding them to the metal lines. I don't think there is much pressure on the cooler lines so you might could uses hoses clamps on your '91. Link to comment Share on other sites More sharing options...
Ronnie Posted February 2, 2017 Share Posted February 2, 2017 After looking on RockAuto I see that the '91 transmission line hoses are crimped onto the steel lines and they are sold as a single unit. Sorry, I don't know of a better place to get them. Did you notice that RockAuto has a Shift Improvement Kit for the '91 model transmissions? I wonder what it does? Link to comment Share on other sites More sharing options...
kdirk Posted February 2, 2017 Topic Author Share Posted February 2, 2017 Ronnie, Thanks. Found an old post on here after locating and searching for the Dorman part numbers (for upper/lower transmission lines), and all (OEM and Dorman) have been discontinued. So, I guess I get to roll my own. Have not seen or heard anything of that shift improvement kit, so know nothing about what it does. I might be able to salvage the current lines by cleaning the rust off (really just light surface rust) and painting it, then having new rubber hose crimped on. Will see what the place I have make hoses has to say about that. I can bend and flare tubing, so maybe I'll fab my own metal pieces and then have the rubber crimped onto those if I can't reuse the current ones. KD Link to comment Share on other sites More sharing options...
fordrodsteven Posted February 2, 2017 Share Posted February 2, 2017 I found a lower trans hose on carparts.com. It says it's "in stock" for $20.05. P/N AC03540435. I have a used lower hose assembly (for a 1988)that I purchased from Jim Finn last year. I don't know if it will fit a 1991. They also list a return/low pressure power steering hose "in stock" for $24.70 P/N GAT370840 Under their "engine" section they list an oil cooler line that looks like it might be the upper line fo the transmission cooler. Also listed "in stock" Dorman P/N RB624034 @ $32.53 Link to comment Share on other sites More sharing options...
kdirk Posted February 3, 2017 Topic Author Share Posted February 3, 2017 Steve, Thanks for that lead. I found several lower trans cooler hoses that are supposed to fit on eBay, but several different part numbers, some GM, some Delco, some other brands as well. 1991 is different from 88, actually is unique from all three previous years. To make matters worse, the GM Buick E platform parts manual 86-92 that I have shows each year has different part numbers, and Rivieras are different from Reattas even. No idea why there are so many variations, since the 88-90 3800 is nearly identical irrespective of the model, and even across Buick/Oldsmobile/Pontiac. The illustrations are nearly useless as they lack the level of detail to tell what the physical differences are. I hate to order something and find it doesn't fit and end up sending it back. I do have a confirmed fit lower trans cooler hose coming from a local auto parts house I deal with, but that is the only one available. Everything else is discontinued and unavailable. eBay has some stuff if you trust the cross reference data they provide (I'm not so confident in their database). But, I pride myself on being a resourceful and determined guy, so I'll figure something out come hell or high water. Kevin Link to comment Share on other sites More sharing options...
Aztec62 Posted February 3, 2017 Share Posted February 3, 2017 After looking on RockAuto I see that the '91 transmission line hoses are crimped onto the steel lines and they are sold as a single unit. Sorry, I don't know of a better place to get them. Did you notice that RockAuto has a Shift Improvement Kit for the '91 model transmissions? I wonder what it does? Hello Ronnie, the 91 Reatta is equipped with a 4T60E Transmission. The "Shift Improvement Kit" RockAuto offers is nothing more than a simple pin. I think this pin is part of the 4T60E variable oil pump output pressure feature. The oil pump contains a slide which pivots around this pin. On high mileage transmissions this pin may show signs of wear wich has an impact on the oil pump pressure and on the way the transmission shifts. Replacing this pin requires to remove the transmission and partly pulling it apart. Not difficult, but lots of work. If you want to make changes to the way the transmission shifts, there is a much easier way: The 4T60 and 4T60E Transmissions have a vacuum modulator which modulates the trans oil pressure in relation to the manifold air pressure of the engine. The newer types of these modulators are adjustable manually. This way you can make the trans shift harder or smoother. The stock original modulator was not adjustable. You will find the modulator when you follow the vaccum line going from the engine throttle body to the transmission. Standing in front of the car, the modulator is at the right front side. It is easy to replace, just one bolt holds it in place. Henning Link to comment Share on other sites More sharing options...
Ronnie Posted February 3, 2017 Share Posted February 3, 2017 Henning, Thanks for the information. Sounds like you really know the Reatta transmissions. Link to comment Share on other sites More sharing options...
Aztec62 Posted February 3, 2017 Share Posted February 3, 2017 Henning, Thanks for the information. Sounds like you really know the Reatta transmissions. Ronnie, my first Buick was a 91 Park Avenue, which has the 4T60E Transmission just like the 91 Reatta. When I got it, the transmission did not work because the planetary gears were broken. I read every bit of documentation available on the internet for the 4T60E and watched all of the 4T60E video on youtube before I tried a repair and overhaul. It was a success, the trans worked fine after my repair. So I know quite a bit about it, but it was only the second time I tried to repair an automatic transmission (First was a Chrysler 41TE from my Sebring convertible). So I would not consider myself an expert. I do not have a lot of experience in trans repair. Most people scare away from it, but actually, it is not that difficult to repair a automatic gearbox or transmission. You wont need a lot of special tools either. What you need is a clean workspace, a good overhaul manual, patience and its good when you are not "all thumbs". I would always prefer a repair and overhaul over the installation of a "good used" trans. You never know what you get. When you repair and overhaul the one you already have, then you know its good. So anybody have a Reatta transmission question, I will be happy to try and answer them. Henning Link to comment Share on other sites More sharing options...
Frogware Posted February 3, 2017 Share Posted February 3, 2017 Hi Henning, A while back my 4T60E wasn't shifting and come to find out my detent/TV cable had been melted from laying on the exhaust. Took me a bit to find a replacement but it works great now. The question I had was; it was mentioned that the detent cable is also used to adjust the shift points is this true, I have been curious ever since. It was also stated that improper adjustment could cause severe damage to the transmission. I'm just wanting to clear things up and satisfy my curiosity. Thanks Scott Link to comment Share on other sites More sharing options...
Aztec62 Posted February 3, 2017 Share Posted February 3, 2017 Hi Henning, A while back my 4T60E wasn't shifting and come to find out my detent/TV cable had been melted from laying on the exhaust. Took me a bit to find a replacement but it works great now. The question I had was; it was mentioned that the detent cable is also used to adjust the shift points is this true, I have been curious ever since. It was also stated that improper adjustment could cause severe damage to the transmission. I'm just wanting to clear things up and satisfy my curiosity. Thanks Scott Scott, when you have a 1990 Reatta and have to adjust a TV cable, you have a 4T60 (also referred to as a 440T4) transmission and not a 4T60E. The difference between the two transmission is this: The 4T60 is almost fully mechanical, only the torque converter clutch is engaged with a solenoid by the BCM. The 4T60E shifts fully electronic with solenoids controlled by the PCM. The 4T60 has a throttle valve (TV) cable, a park/ lock cable and a detent cable. The TV cable connects the accelerator pedal with the throttle valve in the valve body of the trans. The position of the throttle valve determines when the trans shifts up or down. The detent cable connects the shift lever in your car with the manual control valve in the valve body. The manual control valve puts the trans into gear (P-R-N-D-L) The park/lock cable is conncted to the ignition lock cylinder and keeps the engine from getting started when the trans is not in P or N. In a 4T60 trans the shift points are controlled by the position of the accelerator pedal, the MAP in the throttle body of the engine and the actual speed of the car. The 4T60E does not have a TV cable and no park/lock cable. Shift points are determined by the PCM with the help of a number of sensors like throttle position, engine coolant temp. vehicle speed sensor etc. The detent cable works just like with the 4T60 plus a 4T60E has the "PRNDL switch". This switch sends information about the selected shift lever position to the PCM and provides the park/lock function. The adjustment of the TV cable of a 4T60 is important. Here is a good video which explains the adjustment very well: Improper adjustment of the TV cable can in fact damage the transmission in a number of ways: The throttle valve in the trans valve body may get damaged The shift clutches get burned from too early upshifts The tv cable linkage may be damaged. If you want more information on your trans, just google "440T4" or try youtube. Hope this helps, Henning Link to comment Share on other sites More sharing options...
Frogware Posted February 4, 2017 Share Posted February 4, 2017 Scott, when you have a 1990 Reatta and have to adjust a TV cable, you have a 4T60 (also referred to as a 440T4) transmission and not a 4T60E. OOOPS!!! Sorry my bad I didn't mean to include the E on the end, I knew I had the 4T60 and not the 4T60E. Although I did not know the E does not have a TV Cable, interesting how many things were changed between the two. But thank you for the great information it is good to know and a great read. Thanks Scott Link to comment Share on other sites More sharing options...
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